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MARS 
 
 BY 
 
 WILLIAM H. PICKERING 
 
 HABVABD A8TBONOMICAL STATION, JAMAICA 
 
 BOSTON 
 
 RICHARD G. BADGER 
 
 THE GOBHAM PRESS 
 
 HLMV 
 
CoPTBiGHT, 1921, by RicHABD G. Badoeb 
 
 All Rights Reserved 
 
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 Made in the United States of America 
 
 The Gorham Press, Boston, U. S. A. 
 
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PREFACE 
 
 The following list of Collected Papers on Mars con- 
 tains all those of importance prepared by the author 
 between 1890 and 1914. Excepting the first and the 
 last, they are arranged in chronological order. All 
 have been revised, and some of them shortened. No 
 important additions have been made, yet it is beheved 
 that it wiU be found that they represent very satisfac- 
 torily the latest modern views on the physical conditions 
 of the planet's surface. 
 
 William H. Pickering. 
 
 Mandeville, Jamaica, B. W. I. 
 August, 1921. 
 
CONTENTS 
 
 cBApma rAos 
 
 I. Facts About Mars 11 
 
 Peculiarities of the Planet 
 The Shifting Marshes 
 II. Photographs op a Snow Storm on Mars ... 21 
 III. The Glacial Period and the Planet Mars . . 24 
 rv. Colors Exhibited by the Planet Mars ... 26 
 
 V. Changes and Floods on Mars 42 
 
 VI. Mars in 1892 56 
 
 VII. Sohiaparelli's Latest Views Regabdinq Mass . 64 
 The Planet Mars by Giovanni Sehiaparelli 
 
 VIII. The Seas of Mars 97 
 
 IX. Recent Studies of the Martian and Lunae 
 
 Canals 103 
 
 X. An Explanation of the Martian and Lotjab 
 
 Canals 108 
 
 XI. The Double Canals of Mars 113 
 
 XII. The Martian Snows 116 
 
 XIII. What We Know About Mars 120 
 
 The Orbit of Mars 
 
 Gravitation, Water and Atmosphere 
 
 Climate and Meteorology 
 
 Seas, Canals and Lakes 
 
 Duplication of the Canals 
 
 Seasonal Changes 
 
 Is the Planet Inhabited by Intelligent Beings? 
 
 XIV. Different Explanations of the Canals of Mars . 147 
 XV. Signalling to Mars 158 
 
 XVI. The Canals of Mars 162 
 
 XVII. Mars — Things Known and Surmised .... 167 
 Index 17S 
 
MARS 
 
MARS 
 
 CHAPTER I 
 FACTS ABOUT MARS 
 
 1 
 
 Mars is to many persons the most interesting 
 body in the heavens, chiefly because it exhibits phe- 
 nomena that we cannot explain unless v^e assume 
 that life in some form or other exists there. 
 
 Before describing the more recent observations of 
 Mars, it is well to mention a few astronomical facts 
 about the planet that are more or less familiar. 
 Mars revolves in an orbit outside that of the earth 
 in a period a little short of two years, and we over- 
 take it on an average once in every two years and 
 fifty days. I say on an average, because the orbit 
 of Mars is very eccentric, and the time we need in 
 order to catch up with it varies appreciably; it is 
 longer when we overtake it in August than when 
 we do so in February. The date on which we over- 
 take and pass it is called the date of opposition, 
 because the planet is then just opposite the sun, 
 and rises at sunset. In August, when Mars is near- 
 
 ' Youth's Companion, 1917, 91, 639. 
 11 
 
12 Mara 
 
 est the sun, we approach to within 35,000,000 miles 
 of it, but at a February opposition we do not get 
 nearer than 62,000,000 miles. The day of Mars is 
 about forty minutes longer than ours, and the in- 
 clination of its axis to its orbit virtually the same 
 as ours, 23.5°. 
 
 PECULIAEITIES OF THE PLANET 
 
 The diameter of Mars is 4230 miles — only a lit- 
 tle more than half that of the earth; and the force 
 of gravity on its surface is about two-fifths as great 
 as that on the surface of the earth. That fact is 
 of the greatest importance to the life on Mars, for 
 because of it the atmospheric pressure on its sur- 
 face is probably not much more than one-tenth of 
 our own. The boiling point of water on Mars, 
 therefore, is only about 115° ; if Mars were as warm 
 as the earth, water would boil when merely exposed 
 to the sun. 
 
 Snow melts at the same temperature on Mars 
 that it does on the earth, namely 32°. When the 
 north pole of Mars is turned toward the sun, the 
 huge snow fields that surround it melt rapidly, and 
 large dark areas, which sometimes cover two mil- 
 lion square miles, form round them. These are un- 
 doubtedly marshes. 
 
 At times certain parts of the marshes become 
 
Facts About Mars 13 
 
 dark blue in color, and we believe therefore that 
 those parts are lakes. Although they are usually 
 confined to the regions that surround the polar 
 snowcaps, they sometimes appear in other parts of 
 the planet. None of them are permanent, however ; 
 the blue color seldom lasts more than a few weeks. 
 We suppose, therefore, that they are shallow, and 
 that the water evaporates rapidly under the low 
 atmospheric pressure. 
 
 Often great indistinct yellowish-white bodies rise 
 from the marshes and, as the planet revolves on its 
 axis, follow them across the face of the disk. We 
 can hardly doubt that these objects are clouds and 
 fog. 
 
 When the polar caps are melting, the atmosphere 
 of Mars contains as much water vapor as our own, 
 but much less of the permanent gases. Because of 
 that, and of the low temperature of the boiling 
 point, evaporation and condensation occur much 
 more rapidly on Mars than on the earth. As a re- 
 sult their atmosphere at sunrise and sunset is full 
 of cloud, which probably lasts all night. These 
 cloudy nights help to keep the planet warm, and the 
 clear days also tend to warm it up. Except near 
 the equator, however, the climate on Mars must be 
 subject to great extremes of temperature, and its 
 nights are without much doubt bitterly cold. Of 
 one thing we can be quite sure: to beings consti- 
 
 A )s 
 
14 Man 
 
 tuted like ourselves the climate there would be very 
 disagreeable. 
 
 The surface of Mars may be roughly divided into 
 two parts — the dark areas and the bright ones. 
 The dark areas were formerly supposed to be seas 
 and the bright areas continents, but now we know 
 that that is not the case, and that there are no 
 permanent seas on Mars. What seems more likely 
 is that the regions that are permanently dark are 
 areas covered with vegetation ; that those that are 
 temporarily dark are marshes ; and that the bright 
 regions are deserts. Crossing both the dark and the 
 bright regions we find a network of canals — per- 
 haps not so many as are shown by some observers, 
 but certainly a large number. At the junction of 
 the canals with one another, and with the seas, we 
 often find little dark spots, which we call lakes. 
 
 Of course we do not call them canals and lakes 
 in the terrestrial sense of the words. Those are 
 merely names, just as we call dark markings on the 
 planet seas. We do not know yet what the canals 
 and lakes reaUy are, but of one thing we are fairly 
 certain, and that is that they are not water. Prob- 
 ably, Hke the seas, they are strips covered with 
 vegetation. Of course there may be some water in 
 them. The polar seas are really marshes, and the 
 same may be true of the ephemeral canals — those 
 that are short-lived and that soon dry up. 
 
Facts About Mars 16 
 
 Some observers believe that each canal contains 
 a central ditch or pipe by which the canal is irri- 
 gated, and that what we see is the vegetation grow- 
 ing in that irrigated region. They beUeve that the 
 main object of the canals is to conduct water from 
 the polar caps to the great so-called seas, situ- 
 ated in the southern hemisphere of the planet, and 
 that huge engines pump the water through those 
 pipes or ditches. One writer has even gone so far 
 as to compute what horse power would be necessary 
 to accomplish that task, and finds that it would 
 require about four thousand times the amount of 
 power that Niagara gives. 
 
 THE SHIFTING MAESHES 
 
 All these conjectures seem to other observers 
 most improbable. If the snow at one pole of the 
 planet is exposed to continuous sunlight, under 
 which it melts rapidly, it adds a great deal of water 
 vapor to the atmosphere, and so increases the pres- 
 sure; if the other pole is exposed continuously to 
 the terrible cold of interplanetary space, it has 
 scarcely any atmosphere to protect it. We cannot 
 doubt therefore that strong atmospheric currents 
 must pass from the sunlit pole to the other, bearing 
 the water vapor with them. In fact, we know that 
 that is the case, for we can see that the snow is 
 
16 Mars 
 
 transferred from pole to pole and back again every 
 year by a process of distillation and condensation. 
 
 Indeed it seems to me that the hard thing to un- 
 derstand is, not how the water may be transported 
 across the planet, but rather how it may be kept 
 from going too fast and leaving the intermediate 
 surface a waterless desert for a large part of every 
 half year. If the so-called canals have some func- 
 tion to perform in the tremendous transportation 
 scheme on Mars, it is surely not that of conduits but 
 rather that of reservoirs to hold back the flow. 
 For, with the low atmospheric pressure on the planet, 
 the evaporation from every liquid or moist surface 
 must be intense. 
 
 If a current of air bearing moisture sets south 
 from a certain point, let us say a large marsh near 
 the north pole, it will not long retain that direction. 
 When it starts it is moving not only south over the 
 surface but also toward the east with the surface 
 of the planet, as it revolves on its axis. As the cur- 
 rent of air gets farther and farther away from 
 the pole, the underlying surface travels faster and 
 faster; thus the air current that it leaves behind 
 seems to blow toward the west as well as toward the 
 south; that is, it seems to come from the northeast. 
 We are quite familiar with this phenomenon on the 
 earth, under the name of the trade winds. 
 
 When the sun rises on such a polar marsh or 
 
Facts About Mars 17 
 
 lake, the water at once begins to evaporate. It 
 does not generally form a cloud, however, but re- 
 mains a transparent volume of vapor or gas, mov- 
 ing slowly southward. When night falls it con- 
 denses to a cloud, and much of it remains in that 
 condition until the following morning, when we see 
 it following the marsh, and sometimes at one or 
 two hundred miles distant from it. The part of the 
 cloud that does not remain in that condition through 
 the night must be precipitated on the surface as 
 snow. When the sun again rises on it, it will melt, 
 and thus moisten the western or following side of 
 the marsh, whUe the eastern side gradually dries 
 up. If the surface of Mars is very level, as we 
 believe to be the case, and if our reasoning is cor- 
 rect, those marshes should then be found to shift 
 their positions slowly, and to travel southward and 
 westward. 
 
 Now, that is exactly what has been seen to take 
 place. In December, 1913, an observer drew a map 
 to show the marshy region that formed a part of 
 the great marsh surrounding the polar snowcap of 
 Mars. In the following January he again ob- 
 served that region, and made another map. Much 
 to his surprise, he found that the two maps did not 
 agree — that the marshes had shifted slightly toward 
 the west. At first he thought he had made a mis- 
 take, but after a little thought he found the ex- 
 
18 Mar$ 
 
 planation. Since then other polar marshes have 
 been observed, and the same shift has been seen. 
 
 The fact that the polar canals also shift at times 
 with the retreat of the snowcap is one of the rea- 
 sons why we believe that some of the canals are 
 merely marshes. Certain other canals sometimes 
 shift, however, and for no apparent reason, and in 
 no predictable direction. The same is true of the 
 southern permanent seas. The canals are so nar- 
 row that we cannot teU what their color is, but the 
 seas turn from gray to green when the moisture 
 from the polar caps first reaches them ; the color 
 is at times very vivid, so that we feel fairly confident 
 that the seas at least are areas of vegetation. 
 
 If on the earth an area of the size of our New 
 England States should within thirty years change 
 from a fertile plain to a barren desert, we should 
 consider it as a real catastrophe. It is because ap- 
 parent changes of that character do occasionally 
 occur upon Mars, and because similar temporary 
 changes occur frequently, that astronomers find the 
 planet of so much interest. 
 
 The temporary changes are most frequent at the 
 time of the development of the dark regions, which 
 occurs when the polar caps are melting most rap- 
 idly; but astronomers have only begun to study 
 them within the past few years. Since no single ob- 
 server can keep all parts of the planet under con- 
 
Facts About Mars 19 
 
 stant inspection, an association of observers inter- 
 ested in Mars has been formed. These observers 
 are stationed in the United States, in Japan, in 
 Australia, in Asia, in Italy, Denmark, France, and 
 Great Britain. They send in re^lar reports to 
 a central bureau, which publishes the results in one 
 of the astronomical magazines, whence they are dis- 
 tributed to astronomers throughout the world. 
 
 It is easy to measure the length of the canals, and 
 also the breadth of the wider ones, but to measure 
 the breadth of the narrower ones is more difficult. 
 There are many canals from one thousand to two 
 thousand and even three thousand miles long. When 
 they first appear they are often more than two hun- 
 dred miles, broad, but as the season progresses they 
 narrow, and new and much smaller canals appear. 
 We have measured some of these smaller canals, and 
 believe that some of them are less than ten miles 
 wide. The larger lakes situated at the junctions of 
 the canals are sometimes several hundred miles in 
 diameter, but the smallest ones that we can observe 
 are probably no more than fifty. 
 
 As compared with our earth, it is certain that 
 Mars has a scanty supply of several substances 
 needed to support life. One of them is water; the 
 Martian supply of that is certainly less than one 
 one-thousandth of what we have upon the earth. 
 Of course it is true that we have a great deal more 
 
80 Man 
 
 water than we need. Another necessary is nitro- 
 gen, which is needed for plant food. We have at 
 least forty times as much of it for each square mile 
 of land surface as is found upon Mars. Another very 
 important plant food is the gas, carbon dioxide, 
 that our terrestrial volcanoes supply to our vege- 
 tation. If that supply should be cut off, our vege- 
 tation would soon die, and that would be the end 
 of aU animal life upon our planet. Mars is a world 
 more ancient than our own, and it is quite possible 
 that there is little volcanic activity there at pres- 
 ent. If so, carbon dioxide must be in great demand. 
 
CHAPTER II 
 
 PHOTOGRAPHS OF A SNOW STORM ON 
 MARSi 
 
 A box of negatives has recently been received from 
 the temporary Harvard observing station upon Mt. 
 Wilson, California, and contains among other things 
 a number of plates of the planet Mars. Seven 
 views were taken April 9, between 22h. 56m. and 
 23h. 41m., Greenwich mean time. Seven more were 
 taken April 10, between 23h. 20m. and 23h. 32m. 
 Thus the same face of the planet was presented in 
 both cases. Distinct and identifiable spots and mark- 
 ings are well shown in aU the pictures, but in those 
 taken on the latter date a considerable accession is 
 shown to the white spot surrounding the south pole. 
 It has been known for years that the size of these 
 polar spots varied gradually from time to time, ap- 
 parently diminishing in the summer, and increasing 
 in the winter of their respective hemispheres. But 
 I believe that this is the first time that the precise 
 date, and approximate extent of one of these ac- 
 
 ' Sidereal Messenger, 1890, 9, 234. 
 21 
 
22 Mars 
 
 cessions has been observed. The area affected 
 stretches from the terminator, which at this time 
 was in long. 70°, along parallel — 30° to longitude 
 110°, thence to longitude 145°, latitude —45°; 
 thence to the limb which was in latitude — 85° and 
 the 220° meridian, and thence back to the point of 
 starting. It may thus extend also over an unknown 
 area on what was at that time the invisible hemi- 
 sphere of the planet. The visible area included is 
 surprisingly large, amounting to about 2,500,000 
 square miles or somewhat less than the area of the 
 United States. Being near the limb, however, it is 
 not as conspicuous as might at first sight be sup- 
 posed. On the morning of April 9, the area was 
 faintly marked out as if pervaded by haze, or by 
 small separated bodies, too small and too far apart, 
 or too faint to be recognized individually. But on 
 Apidl 10 the whole region was brilliant, fuUy equal- 
 ing that surrounding the north pole. In the mean- 
 time a much smaller area on the limb which on the 
 9th was very bright had either vanished or joined 
 the main mass, by moving eastwardly, as we should 
 say, considering Mars as a globe. 
 
 The date of these events corresponds to the end 
 of the winter season on the southern hemisphere of 
 Mars, or what would be with us about the middle of 
 February. The numerical data given above are 
 
Photographs of a Snow Storm on Mars 23 
 
 founded on the extremely useful tables published by 
 Mr. Marth in the Monthly Notices. 
 
 As to what these observations mean, might most 
 naturally be explained by terrestrial analogies, but 
 be that as it may, the facts are that these appear- 
 ances are conspicuous upon each of the fourteen 
 photographs, and so distinctly so, that no one who 
 had once seen them would hesitate an instant in de- 
 ciding on which day any particular plate was taken. 
 
CHAPTER in 
 
 THE; GLACIAL PERIOD AND THE PLANET 
 MARS^ 
 
 It seems to me that one of the chief secondary 
 causes of the Glacial Period, as based on an increased 
 eccentricity of the Earth's orbit, has not heretofore 
 been sufBciently enforced. During the short winters 
 and long summers, whatever precipitation occurs will 
 be largely in the form of rain. On the other hand, 
 during the long winters and short summers it wUl 
 be, on the whole, mainly in the form of snow. Now 
 the snow by its great reflective power will cause 
 the earth to lose a very large proportion, perhaps 
 nearly three-quarters, of whatever radiant energy 
 does fall upon it. Moreover, during the short sum- 
 mer, when the sun is able to melt the snow, there will 
 be an extensive evaporation from its whole surface, 
 forming clouds. These wiU in their turn reflect away 
 the sun's rays, and at the same time by their shade 
 protect the snow beneath them from melting. 
 
 This cause requires for its action the presence of 
 
 " Knowledge, 1892, 113. 
 
 24 
 
 \ 
 
The Glacial Period and the Planet Mars 25 
 
 considerable moisture upon the surface of the planet. 
 It has been stated that the glacial theory does not 
 appear to apply to Mars. In the case of this planet, 
 however, we have good reason for thinking that it 
 formerly had extensive oceans upon its surface, and 
 the gradual cooling to which it has been subjected 
 has enabled room to be formed for them in its in- 
 terior; that is to say, there are probably extensive 
 regions in its interior which are not sufficiently hot 
 to convert water into steam. The water would there- 
 fore, naturally, as is the case with the earth, go un- 
 derground, filling all the microscopic cavities be- 
 tween the rocks. Be that as it may, the appearance 
 of the surface of this planet leads us to think that 
 it possesses at present very much less water in pro- 
 portion than does our earth. That being the case, 
 there could not be sufficient evaporation to form the 
 extensive snow-caps required by the glacial theory. 
 As an illustration of this point, we should expect that 
 the northern or continental slopes of the Himalaya 
 Mountains would be colder but also drier than the 
 southern ones, which are exposed to the ocean. Yet 
 upon the warm southern slopes we find the line of 
 perpetual snow considerably lower than upon the 
 colder northern ones. Thus, because the supposed 
 snow-caps upon Mars are small, it does not neces- 
 sarily indicate that the temperature of the planet 
 is higher than that of the earth. 
 
CHAPTER IV 
 
 COLORS EXHIBITED BY THE PLANET 
 MARS^ 
 
 The following preliminary account of an investi- 
 gation made ia Cambridge at the last opposition of 
 Mars, is published at this time, in the hope that 
 others may take advantage of the present favorable 
 circumstances, to verify the results here described. 
 One of the most difficult branches in practical as- 
 tronomy is that pertaiuiag to the colors of the heav- 
 enly bodies, for no other optical illusions can be 
 found to be so complete as those pertaining to color. 
 The planet Mars is frequently spoken of as the red 
 planet, yet its color is by no means as red as that of 
 an ordinary candle flame. To illustrate this fact, let 
 the observer so place himself that the planet Mars, 
 an electric Ught, and a candle or gas flame, all ap- 
 pear to him to be of the same brilliancy. He will 
 then find that while the planet is redder than the 
 electric light, it is bluer than the candle flame, and 
 is, in fact, very nearly half way between the two in 
 
 'Astronomy and Astro-Physics, 1893, 11, 449. 
 26 
 
Colors Exhibited by the Planet Mars 27 
 
 color. If either source of light is made brighter 
 than the other, its tendency is to appear whiter. 
 
 During the last opposition, sixty paintings were 
 made of the planet, with the 12-inch Harvard re- 
 fractor, and sixty-six uncolored drawings. They 
 were all constructed upon a uniform scale of 
 800 000 000 ' ^^^ planet being represented by a disc, 
 34 millimeters in diameter. Usually powers of 
 200 to 400 were employed. It was found that in the 
 evening, the most prominent and striking color of 
 the planet could be represented very well by car- 
 mine. It was also found that it could be equally well 
 represented by golden yellow. When painted in the 
 day-time it was orange, with more or less carmine, 
 depending on various circumstances. If a high 
 power was used it was much redder than with a low 
 power. All of these changes may be readily ex- 
 plained by the elementary principles of physics, but 
 they illustrate very well some of the difficulties that 
 were presented by the research. As the planet is 
 illuminated by sunlight, it is evident that in order 
 to obtain a correct result, the pigment used to repre- 
 sent it should be illuminated by the same source. 
 The paintings should, therefore, be made in the day- 
 time. 
 
 Experiments were also made in a darkened room, 
 the only light transmitted being through a small 
 round hole bored in the shutter. Various pieces of 
 
28 Mars 
 
 colored stone were placed upon a mirror, which 
 reflected the light of the sky into the room. Reflec- 
 tions of these stones were then viewed in two pieces 
 of flat glass, supported inside the room. By varying 
 the angles of the glasses, the intensity of the sun- 
 light reflected from the stones could be varied, so 
 as to render them either brighter or fainter than the 
 planet, as seen in the telescope. Paintings of the 
 planet, illuminated by the same light as that used 
 in the evening, were then compared with the light 
 from the stones. 
 
 The other shutters of the room were then opened, 
 and the paintings illuminated by daylight. It was 
 found that the same laws of color held good with 
 the stones that had been previously found appli- 
 cable to the planet. The various stones tried were 
 a piece of brown lava from Vesuvius, a piece of red 
 basalt, a piece of brown sandstone, a piece of very 
 red granite, and two pieces of brick, one an orange 
 red, and the other the color of dragon's blood. The 
 former may be best represented by dragon's blood 
 with a little Saturn red in it. The red granite, which 
 is half way in color between the two pieces of brick, 
 is well represented by dragon's blood and sienna, 
 half and half. It was found that this piece of gran- 
 ite under suitable illumination could be made to 
 match exactly any of the paintings of the planet. 
 As its color was not far from that of an average 
 
Colon Exhibited hy the Planet Mars 29 
 
 brick, our next experiment was to select a distant 
 building made of brick of the proper color, and make 
 a painting of it as seen in the telescope. This paint- 
 ing was necessarily made by daylight, and another 
 telescope had to be used, as the building was not 
 visible from the dome of the 12-inch. The building 
 selected was two and a half miles distant. The tele- 
 scope employed was a 6-inch refractor by Clacey. 
 The result was as anticipated, that when the paint- 
 ing of the building was compared with some of the 
 daylight paintings of Mars, the colors were identical. 
 In each case the colors were separately mixed at 
 the time, although the components were the same, 
 and in each case the result exactly satisfied the eye. 
 The reason that a red planet or distant brick 
 building can be matched by daylight with an orange 
 pigment is because of the bluish white light reflected 
 from the atmosphere, lying between the distant ob- 
 ject and the eye, which is mixed with the red light 
 coming from the object, changing it from red to 
 orange. If the brick is examined close at hand, a 
 red pigment must be employed to represent it. When 
 the planet is viewed at night, or when a piece of brick 
 near at hand is illuminated by sunlight, but the 
 pigment is illuminated by a yellow artificial light, 
 this light by enforcing the red components of the 
 pignient, and absorbing the blue, makes the pigment 
 really appear red, and therefore match the Sun- 
 
30 Mars 
 
 illumined object. The object, therefore, although 
 painted yeUow by night, reaUy appears to the eye 
 redder than when painted orange by daylight. This 
 fact was well brought out by an experiment made 
 at night, employing the magnesium light instead of 
 the oil lamp as a source of illumination for the pig- 
 ment. In that case the color best matching the 
 planet was found to be dragon's blood which, as we 
 have seen before, is probably not far from its true 
 color, which we considered to be the same as the 
 red granite, and therefore to be represented by equal 
 parts of dragon's blood and sienna. 
 
 But red is by no means the only color visible upon 
 the planet. When near the limb, the reds always 
 appear yellowish, indicating probably an atmo- 
 spheric absorption of the red portion of the spec- 
 trum, an effect quite at variance with the action of 
 our own atmosphere, which tends to absorb the blue 
 rays. 
 
 Next to the reds and yellows, the most important 
 colors are the grays and greens. The latter colors 
 one would actually at first attribute to an optical 
 illusion, due to contrast with the prevailing tint. 
 If this were the case, however, these portions of the 
 planet should be painted blue, blue being the com- 
 plementary color of the orange seen by daylight. 
 Blue pigment seen by lamp light becomes green, 
 which is the complementary of the red seen at night. 
 
Colors Exhibited by the Planet Mars 81 
 
 Therefore in either case blue would be the comple- 
 mentary color and not green. Experiments under 
 both of these conditions, however, made upon sev- 
 eral occasions, conclusively showed that these greens 
 could not be matched by blue pigment of any tint, 
 but were a true and genuine green. Although rare, 
 yet upon four occasions it was noted that green 
 was the most conspicuous color visible. This was 
 due sometimes to its covering a large area, and some- 
 times to its being a more intense color than the red. 
 This also indicated that the green could not be due 
 to contrast. It was found by experiment that the 
 effect upon green pigment produced by using an 
 artificial illumination was very much less marked 
 than upon red, the only effect being, that when so 
 illuminated, it appeared rather more yellow than 
 when seen by daylight. This would imply that the 
 greens upon Mars were in reality slightly more yel- 
 lowish than the evening paintings would indicate. 
 
 When the seeing became bad the greens and reds 
 united to give a whitish tint, and the colors dis- 
 appeared. This further indicated that the greens 
 were not due to contrast. A piece of black paper 
 was introduced into the field of view of the telescope, 
 cutting off the red, but the green color remained 
 unchanged. An examination was made of Jupiter, 
 the disc being a bright yellow, but no green could 
 be detected upon it. The greens, especially the light 
 
32 Mar$ 
 
 greens, usually appeared near the poles, which were 
 necessarily near the edge of the disc, but on these 
 occasions a region near the center was seen of a light 
 green color. The green could not therefore be at- 
 tributed to the secondary spectrum of the glass. 
 Moreover, the telescope was thrown alternately 
 slightly in and out of focus, changing the color of 
 the outside fringe of light, but without altering the 
 green hue upon the disc. 
 
 The green was not due to atmospheric refraction 
 since it was seen near both poles, besides which the 
 color due to this cause is easily overbalanced by that 
 due to the lack of achromatism in the eyepiece when 
 the planet is placed near the edge of the field. The 
 green is not due to an optical illusion caused by the 
 brightness of the snow. It is sometimes seen between 
 the snow and the red regions of the planet, and is 
 also seen when the snow is not visible. Indeed I think 
 it has been often mistaken for the snow, as it is a 
 much larger and more conspicuous object. The real 
 snow is much more difficult to see than is generally 
 supposed, and is frequently not visible at all. I have 
 only seen it occasionally when it was readily dis- 
 tinguished by its extreme brightness and whiteness. 
 An excellent idea of its appearance is given in 
 Chambers' Astronomy, fourth edition, and I have 
 seldom seen it of much greater extent. The draw- 
 ing is by Green, and like all of his work upon Mars, 
 
Colors Exhibited hy the Planet Mars 33 
 
 is most accurate and life-like. The gray objects 
 upon Mars, when the seeing was poor, acquired a 
 slightly yellowish, and in the day-time a brownish 
 tint, owing to their confusion with the surrounding 
 regions, but when the seeing was good, they were 
 either a pure gray, or of a slightly greenish color. 
 This does not apply to all the darker regions, as 
 we shall see later. There was no difficulty in obtain- 
 ing distant green terrestrial objects to study through 
 the telescope, and it was found that even upon very 
 clear days, when over two or three miles distant, 
 they appeared either gray or greenish gray. This 
 was particularly true of the darker shades. In fact 
 I never at any time saw any colors as brilliant as 
 the bright greens upon Mars. Even when a piece of 
 bright red paper was introduced into the field of 
 the telescope, no appreciable contrast effect was 
 produced upon the terrestrial greens. This fact, 
 together with the other that the greens on Mars 
 were seldom seen by daylight, made me think that 
 those seen upon the planet must be due to some 
 illusion, whose origin had not as yet been eliminated, 
 for one cannot well conceive of more vivid greens 
 than those due to some of our own vegetation. I had 
 been observing a tree some two and a half miles 
 distant with the telescope one very clear morning, 
 when I noticed that there was an electric lamp just 
 by the side of it. That evening I pointed the tele- 
 
34< Mars 
 
 scope again on the tree, and it instantly shone out 
 a most brilliant bluish green, fully equalling in in- 
 tensity anything I had seen upon the planet, and a 
 trifle bluer. This explained why it was that in the 
 day-time I had only detected the greens upon Mars 
 with difficulty while at night they were conspicuously 
 visible, — the white light reflected by our own atmo- 
 sphere had corrected them into grays. 
 
 Numerous observations were made of the colors 
 of particular regions, especially of those which ap- 
 peared very dark in tint. Attempts were also made 
 to determine the color of the canals. This latter 
 is an extremely difficult undertaking, as the smaller 
 the area, the harder it is to assign any particular 
 color to it. The apparent area of any very small 
 region always strongly affects one's judgment of its 
 color, and in comparing two colors, it is most im- 
 portant that their apparent areas should be equal. 
 Regarding the colors of these smaller regions, as it 
 is very desirable that the opinions of others be 
 formed independently of my own, I will defer de- 
 scribing them until another paper, merely stating 
 that there is some evidence that certain regions do 
 not seem to remain at all times of the same color. 
 
 In closing, I shall mention that these colors have 
 been seen through three different telescopes, 12-inch 
 and 15-inch at Cambridge, and more recently 
 through the 13-inch instrument at Arequipa. The 
 
Colors Exhibited by the Planet Mars 35 
 
 latter instrument brought them out very finely, the 
 greens showing well even in the day-time. On April 5, 
 I could see the great canal north of the Syrtis Major 
 with a power of 810 diameters. It will be noted 
 that in what precedes I have carefully abstained 
 from advocating any hypothesis regarding the true 
 sources of any of the colors, merely confining myself 
 strictly to a statement of the observed facts. 
 
 In my former paper upon this subject, attention 
 was called to the important effect of our own at- 
 mosphere in misleading our judgment as to the true 
 colors exhibited by the heavenly bodies. A good 
 illustration of this effect may be obtained from a 
 mountain summit upon a slightly cloudy day. The 
 distant greens of the landscape, which are by no 
 means as brilliant as when viewed close at hand, are 
 at once changed to grays either by the passing over 
 them of a cloud shadow, or by the passing of a very 
 thin mist between them and the eye. In the former 
 they become darker, and in the latter lighter, but 
 in either case the greenish tint entirely disappears. 
 
 The sudden changes of color exhibited by some 
 of the smaller areas upon the planet Mars are some- 
 times almost startling. A recent view was obtained 
 shortly before sunrise, when the snowy region about 
 the south pole appeared of a most brilliant green, 
 quite equalling in color the rather narrow green 
 band situated just to the north of it. Later as the 
 
36 Mars 
 
 Sun came up, the color of the snow changed to bright 
 yellow, the rest of the disc changing in the mean 
 time to orange. Later the seeing improved, several 
 of the canals became visible, and the snow became as 
 colorless as that upon our surrounding mountains. 
 The two former effects were probably due to bad 
 seeing, the fluctuations of our own atmosphere super- 
 posing the colors of the surrounding regions upon 
 the snow. We have laid it down as a rule never to 
 rely greatly upon our color observations unless the 
 snow caps of the planet appear perfectly colorless, 
 and the canal system is well defined. These condi- 
 tions we find always combined with the best seeing. 
 For these delicate color observations it wiU therefore 
 be seen, that not only do we require a telescope of 
 the very first quality, but also the very best obtain- 
 able atmospheric conditions. 
 
 In studying the smaller dark regions, such as 
 the northwestern part of the Syrtis Major, great 
 differences of color have been noted from night to 
 night, and I have colored sketches in my possession, 
 taken at difi^erent times, in which it is represented 
 as grey, as green, as blue, as brown and even as 
 violet. The latter color was so extraordinary that I 
 endeavored to make that portion of the planet ap- 
 pear to my eye of some other color, but it was 
 impossible, and no other color but violet lake could 
 be made to match it. This color upon the planet 
 
Colors Exhibited hy the Planet Mars 37 
 
 has only been seen by me upon one occasion since. 
 The brown color above noted was undoubtedly due 
 to bad seeing. At one time I felt convinced that 
 the real color of the darkest spots upon the planet 
 was a deep blue, and this may in reality be the case, 
 but of late, under the most favorable circumstances, 
 they have appeared to me of an absolutely colorless 
 dark grey. Probably this point can be settled at 
 the present opposition. 
 
 Before describing the colors of particular regions 
 more at length, it may be well to give a description 
 of the general characteristics of different longitudes, 
 as observed during the opposition of 1890. For this 
 purpose we may divide the surface of the planet 
 into six sections, each sixty degrees of longitude in 
 breadth, the first having the 0° meridian central. 
 The times of transit of the 0° meridian of the planet 
 may be readily computed, but the amateur will find 
 them given in cpnvenient shape in the excellent 
 ephemerides published by Mr. Marth in the Monthly 
 Notices. The only pity is that these ephemerides 
 cannot appear about six months earlier, in order to 
 be of the most use to astronomers outside of the 
 British Islands. 
 
 The most striking marking upon the planet, and 
 that most readily seen with a small telescope, is the 
 Syrtis Major, or Y mark. This is nearly central 
 in the sixth position of the planet, with the 300° 
 
88 Mars 
 
 meridian in the middle of the disc. Owing to the 
 period of rotation of Mars heing 37 minutes longer 
 than that of the Earth, in about six nights Mars 
 wiU be found at the same hour in the fifth position 
 with the 240° meridian central. This region in 1890 
 was interesting as containing the most conspicuous 
 canals visible upon the planet, excepting the large 
 one which terminates the Syrtis Major upon the 
 north. At this opposition these canals will aU be 
 too far north to be well seen. The fourth and third 
 regions of the planet were both extremely uninterest- 
 ing as showing very little detail of consequence. 
 The second position with the 60° meridian central 
 was interesting as showing the great southern ocean, 
 which is nearly as conspicuous as the Syrtis Major 
 itself. In the first position with the 0° meridian 
 central the ocean is disappearing and the Syrtis 
 Major coming into view. 
 
 We now come to a curious feature of the observa- 
 tions, namely, the actual changes in color which, 
 eliminating all probable sources of error, the sur- 
 face of the planet really seems to undergo. When 
 the Syrtis Major is central, before the autumnal 
 equinox of the northern hemisphere, the region to the 
 east is seen to be distinctly more greenish than that 
 to the west. As the season wears on the difference 
 in color becomes less marked, and the greenish hue 
 is confined more closely to the region immediately 
 
Colors Exhibited by the Planet Mars 89 
 
 bordering the Syrtis on the east. In most of my 
 drawings made in 1890 the two arms of the Syrtis 
 are shown of equal breadth. This appears to be 
 the case also upon Green's map published in Cham- 
 bers' Astronomy, although this point is not well 
 shown by him. At present there is no doubt but that 
 the eastern arm is much the wider of the two, per- 
 haps twice as wide. Early in 1890 the entire region 
 enclosed between the arms of the Syrtis Major, as 
 far as the snow cap, was of a brilliant green color. 
 On June 27, however, or eleven days before the 
 vernal equinox of the southern hemisphere, a yellow 
 spot appeared at the extreme northern point of the 
 triangular area. As the season advanced this yellow 
 spot increased in area, till it covered the whole 
 region as far south as could be seen. This year when 
 first observed, this area was entirely green, but on 
 May 9, or seventeen days before the vernal equinox, 
 the yellow or perhaps reddish spot appeared in the 
 same place, and it will be interesting to determine 
 if, as the season advances, this color again pro- 
 gresses towards the pole. Changes to the east of 
 the Syrtis Major have also been noticed by Schi- 
 aparelli. These he ascribes to extensive floods. On 
 June 8, 1890, thirty days before the autumnal equi- 
 nox in the northern hemisphere, there was a large 
 greenish area visible in longitude 180°, latitude 30° 
 north. By July 16, or eight days after the equinox, 
 
40 Mars 
 
 this spot could not be found, the whole region ap- 
 pearing of a yellow tint. In longitude 10°, latitude 
 40° north, is a large crescent-shaped area. In June 
 and July, 1890, it was well seen and appeared quite 
 as dark as the great southern ocean. This was noted 
 upon a number of occasions. It was however painted 
 green, and the ocean to the south of it blue, the 
 difference in color on one evening being very clear, 
 as seen by my assistant, Mr. A. E. Douglass, and 
 myself. On March 22 of the present year the cres- 
 cent was well shown, but was markedly fainter than 
 the ocean, which was again suspected of being blue, 
 but the color could not be satisfactorily confirmed. 
 This crescent is now too far north, owing to the 
 motion of the planet, to be satisfactorily studied. 
 
 While these indications of change of color upon 
 the planet are too few and isolated at present to 
 enable us to form a satisfactory explanation of their 
 causes, they still hold out a promise that should 
 these observations be carefully repeated at future 
 oppositions, under suitable conditions, we may in 
 time be able to deduce the laws affecting them, and 
 perhaps even predict their changes in advance. Too 
 much stress however cannot be laid on the danger 
 of optical illusion in this matter. It is generally 
 considered that a very good instrument, and some 
 practice is required, before an observer can cer- 
 
Colors Exhibited by the Planet Mars 41 
 
 tainly see the canals even, but in order that satis- 
 factory results in this branch of the research may 
 be achieved, the more important canals must be seen 
 with distinctness, and the snow caps, if present, 
 must appear perfectly colorless. 
 
CHAPTER V 
 CHANGES AND FLOODS ON MARS ^ 
 
 In the previous chapter an endeavor was made to 
 show that actual changes do occur upon its sur- 
 face, besides the well known annual change in the 
 size of the snow caps. This effort has perhaps 
 proved unnecessary since the changes which have 
 actually occurred at the present opposition have 
 been so conspicuous and startling that they might 
 easily be detected even by the possessors of six-inch 
 telescopes. The canals can now be observed read- 
 ily any evening. Many of those that we have seen 
 here agree with Schiaparelli's, and several do not. 
 Several of his more strongly marked ones have not 
 been found at all. This, however, I am quite pre- 
 pared to attribute to seasonal changes. Some very 
 well developed canals cross the oceans. If these are 
 really water canals and water oceans, there would 
 seem to be some incongruity here. When the snow 
 melts, it seems that there reaUy should be some 
 oceans, and a careful study has been made of the 
 
 ' Astronomy and Astro-Physics, 1892, 11, 668. 
 42 
 
Changes <md Floods on Mars 43 
 
 dark spot previously referred to, at the northern 
 end of the Syrtis Major. Although sometimes dark 
 gray, yet in the great majority of cases when the 
 seeing is satisfactory, and the spot is central, it 
 appears of a clearly defined dark blue color. An- 
 other spot presenting a precisely similar appearance' 
 occupies a portion of the Sinus Sabaeus or Herschel 
 Strait. 
 
 These two spots when near the limb have on sev- 
 eral occasions been observed to be of a beautiful 
 bright blue color. If they are really oceans, they 
 must, under these circumstances, be reflecting to our 
 eyes the color of the Arean atmosphere, as water 
 would, under similar conditions, do upon our Earth. 
 
 Viewed with a double image prism these spots 
 when near the limb seem to present faint traces of 
 polarization, the plane being radial to the planet. 
 Until very recently they were much darker than any 
 other spots visible, although a dark region near 
 SoUs Lacus (Terby Sea) has upon one occasion ap- 
 peared quite black. It is my impression that these 
 two areas are really water, and in the present arti- 
 cle they wiU be referred to provisionally as the 
 Northern and Equatorial Seas respectively. As I 
 have stated in former articles I very much doubt 
 if what are usually known as oceans and canals con- 
 tain any water at aU. That is to say, any water 
 which is visible as such, for it is quite possible and 
 
44! Mars 
 
 perhaps probable that they may owe this color in- 
 directly to the presence of water, stationary or run- 
 ning. 
 
 The boundaries of the Equatorial Sea (Fig. 2) 
 are all sharply defined. It is 1,300 miles in length, 
 east and west, and averages a trifle over 200 miles 
 in breadth, with two deep bays slightly curved, and 
 almost precisely alike, opening southward, at its 
 western end. In this article I have adopted the 
 precedent set by Professor Schiaparelli in applying 
 the terms east and west with the same signification 
 as is given to them in maps of the Earth. That is 
 they are reversed as compared with other celestial 
 maps. Its total area is 275,000 square miles. The 
 shape of the Northern Sea (Fig. 3) is that of an 
 irregular quadrilateral, 750 miles in length by 600 
 in breadth. On the north its outlines are as clearly 
 defined as those of the other sea, but on the south 
 it is bounded by a dark gray region, never seen 
 hitherto to be blue and which I am inclined to 
 ascribe for reasons which wiU appear later to low 
 land. If its shores were indented, this might ac- 
 count for their rather indistinct appearance. Its 
 area is nearly equal to that of the Equatorial Sea, 
 being approximately 225,000 square miles. What 
 we may therefore speak of as the permanent water 
 area upon Mars amounts to about half a million 
 square miles. This is exactly one-half the area of 
 
Chcmges cmd Floods on Mars 45 
 
 the Mediterranean Sea. A glance at the map of the 
 world in two hemispheres will give the reader an idea 
 of the enormous disparity in the water area of the 
 two planets. From this circumstance we might ex- 
 pect the climate of the smaller planet to be on the 
 whole much the dryer of the two, and if all is not 
 a desert, at least that the deserts would be much 
 more prominent than upon the Earth. 
 
 In this connection we may refer to the green 
 areas situated near the poles, and described at some 
 considerable length in the previous chapter. It 
 was there stated that after the vernal equinox the 
 greens almost entirely disappeared and the ques- 
 tion was raised whether the same effect would be 
 noticed this year. We can now reply in the af- 
 firmative, for although we have searched for them 
 with the utmost care of late, when the seeing was 
 both better and worse than before, scarcely a trace 
 of them have we been able to detect. There is also 
 a green area to the west of the Equatorial Ocean, 
 but this region we have not been able to inspect care- 
 fully of late. In case they should reappear before 
 the present opposition is over, as is possible, it is 
 hoped that others will be upon the watch to detect 
 them, and accurately locate their positions. While 
 their reappearance might with some show of prob- 
 ability be attributed to the presence of one of the 
 great branches of organic life upon the planet, 
 
46 Mars 
 
 and with this branch, as an ahnost necessary corol- 
 lary, the other one, we must still consider the mat- 
 ter merely in the light of a tentative hypothesis, 
 until further observations are accumulated, and 
 content ourselves with the statement that no facts 
 have as yet been observed inimical to this idea. The 
 one fact which we have so far attempted to demon- 
 strate is the presence upon the planet of water in 
 the liquid form, and the attempt has been made to 
 determine its exact location, and the area and shape 
 of the surfaces permanently covered by it. 
 
 As might have been expected from the position 
 of the planet's axis, the snow cap is much more 
 conspicuous at this opposition than it was at the 
 last. On June 23, the northern limit of the south- 
 em polar snow cap was, on the average, in latitude 
 — 65°. This in our northern hemisphere would 
 correspond to the latitude of northern Siberia, Ice- 
 land, and northern British America. As this date 
 was but thirty days after the passage of the vernal 
 equinox, it will be seen that the line of melting 
 snow was rather nearer the pole than we might ex- 
 pect to find it upon our own Earth at the same 
 period. The area of this snow cap was some 2,400,- 
 000 square miles. Upon this date a small dark spot 
 was noted near the center of the snow. The spot 
 was then well developed, and must have been already 
 existing for several days. Since that time it has 
 
Changes and Floods on Mars 47 
 
 grown rapidly, soon splitting the snow cap into two 
 unequal parts, and of late changing its shape ma- 
 terially. The snow cap in the meantime has rap- 
 idly diminished in size, so rapidly in fact, that con- 
 sidering the weakened power of the sunlight at that 
 distance, we are forced to believe that its depth is 
 much less than that of the similar deposit covering 
 the poles of our Earth. It will thus be seen that 
 the comparatively small snow caps of Mars by no 
 means necessarily imply a warmer climate than that 
 of the Earth, as some writers have assumed, but 
 merely a drier one. If the snow fell to a less depth, 
 a larger proportion of the heat absorbed in the 
 higher latitudes could be employed in raising the 
 temperature, and a less amount absorbed in the lat- 
 ent form. This would involve a somewhat higher 
 temperature during the summer, but a longer period 
 of intense cold during the winter, than exists upon 
 the Earth, in proportion to the length of the year. 
 
 Upon July 26 it was found that the area of the 
 snow cap had diminished to 800,000 square miles. 
 An area of 1,600,000 square miles of snow had, 
 therefore, been converted into water, in the space of 
 thirty-three days. With our extensive oceans this 
 would produce no material change upon the Earth, 
 but what must be the effect upon Mars, whose total 
 permanent water area amounts to less than one- 
 third of this figure.'' Moreover, upon the Earth the 
 
48 Mars 
 
 semi-annual transfer of the melted snow from pole 
 to pole is conducted by means of the oceans, but 
 upon Mars this transfer must take place across the 
 land. We should naturally expect that a consider- 
 able proportion of the water would be absorbed or 
 deposited upon the way. It will therefore be in- 
 teresting to notice what has actually been observed. 
 Eastward of the stem of the Y*, in what is known 
 as Libya, there was observed by Mr. A. E. Douglass 
 upon May 8, and by myself quite independently, 
 upon May 9, a light colored triangular region with 
 a bright triangular center (Fig. 1). The angles of 
 the central region were so distinct that they were 
 selected as stations for our micrometric survey of 
 the surface. At the next presentation of this phase, 
 a month later, the central triangle had entirely van- 
 ished, being of the same tint as the outer triangular 
 area, thus rendering it quite impossible to employ 
 the selected stations. The whole area was, however, 
 still much lighter than the stem of the Y. June 11, 
 it had a decidedly greenish gray tint when central, 
 and two days later it had assumed the same gray 
 color as the stem of the Y from which it was indis- 
 tinguishable. July 17, that portion of this region 
 south-east of the Northern Sea had become extremely 
 dark (Fig. 4), being only exceeded in tint by the 
 sea itself, which differed from it mainly in color, the 
 sea being blue and this region gray. 
 * The Syrtis Major. 
 
Fig. I 
 May 9, Sib 05m 
 
 Fig. 3 
 July 16, 17h 45m 
 
 Fig. 5 
 July 33, ITh 30m 
 
 Fig. 2 
 July 14, 16h 50m 
 
 Fig. 4 
 July 17, 15b 50m 
 
 Fig. 6 
 July 25, sob 40m 
 
 Note in Regard to the Figures. In the above figures north 
 is placed at the top. The date is given in Greenwich Mean 
 Time. The scale is 200 kilometers (125 miles) to the milli- 
 meter. In the last five figures 1" = 1.4 millimeters. 
 
 49 . _,. -.^ 
 
50 Mars 
 
 Upon July 10, the region south-west of the Equa- 
 torial Sea was extremely faint, and but little darker 
 than the reddish region to the north of it. A simi- 
 lar effect had been suspected in June. This seems 
 the more singular, since after the Seas this is usually 
 one of the very darkest and most conspicuous mark- 
 ings upon the planet. The region west of this has 
 also been subject to various changes, which need not, 
 however, be described in the present article. 
 
 Upon May 12, it was noticed that the southern 
 snow cap was bounded by a very fine black line. By 
 June 23 this had become quite conspicuous in some 
 places. By July 10, that portion of the line lying 
 upon the Arean meridian was as dark as the Equa- 
 torial Sea, and appeared quite like it. On July 16, 
 a small elongated black spot was noticed upon the 
 western side of the stem of the Y (Fig. 3). It was 
 then so conspicuous, that I was surprised I had not 
 noticed it before. My measurements indicated that 
 it was about 125 miles in length by 75 miles in 
 breadth. This would make it of about the same size 
 as Lake Erie, and it was connected with the North- 
 ern Sea by a very narrow straight black line. This 
 line did not at all resemble the so-called canals, be- 
 ing much finer and blacker. This spot was again 
 seen by myself upon July 17, and by Mr. Douglass 
 upon July 22, after which it disappeared unex- 
 pectedly in a way which I shall presently relate. 
 
Changes amd Floods on Mars 51 
 
 Changes were now coming thick and fast upon the 
 planet, and when evening came round, and we put 
 our eyes to the telescope, we never knew what we 
 should see next. In my August paper reference is 
 made among other suspected changes to the two 
 arms of the Y, which in the opposition of 1890 were 
 always drawn of approximately equal width. The 
 statement was then made: "At present there is no 
 doubt but that the eastern arm is much the wider 
 of the two, perhaps twice as wide." This paper was 
 completed May 13, 1892. This statement still re- 
 mained true upon June 10 and 11, but at the next 
 presentation upon July 12, a central arm was shown, 
 converting the Y into a trident. This arm connected 
 directly with the dark streak or split in the snow 
 cap (Fig. 2). The eastern arm was still much the 
 widest, but in two days the difference between it and 
 the western was much less marked, and by July 17, 
 they were equal in breadth, just as they appeared 
 in 1890 (Fig. 4). In the meantime the central arm 
 of the trident had become much more prominent, 
 being about equally conspicuous with the other two, 
 and now, to my astonishment was seen a large dark 
 area south-east of the Northern Sea and of fully 
 double its area. This dark region is the one re- 
 ferred to earlier in this paper as having formerly 
 been very light colored. It was now nearly as dark 
 as the Sea, and much darker than that part of the 
 
52 Mart 
 
 Y to the south of it. In color it was gray, and not 
 blue. This observation was independently confirmed 
 by Mr. Douglass the next evening. By July 23, this 
 darkening had greatly diminished, the color of the 
 dark region being of the same depth as that of the 
 rest of the Y (Fig. 5), which latter had now mate- 
 rially changed its shape, owing to eastward exten- 
 sions of the eastern arm. In the meantime the cen- 
 tral arm, recently so strongly marked, had com- 
 pletely disappeared. But what was most extraordi- 
 nary was that the Northern Sea had now extended 
 far to the south-west, completely concealing the lit- 
 tle lake and the channel connecting the two. This 
 result was also confirmed independently by Mr. 
 Douglass the next evening. By "independently" I 
 mean that he made his drawing without having seen 
 mine, or knowing at all what I had seen. Indeed, 
 both of us were doing so much observing at this time 
 that we had little opportunity to compare results, 
 and, unfortunately, did not fully appreciate the ex- 
 tent of the changes we were observing, and so de- 
 voted a considerable share of our attention to other 
 matters. This will account for the apparent breaks 
 in this record, for, with the exception of July 9, 
 when some repairs were being made upon the tele- 
 scope, continuous observations have been main- 
 tained since July 4. 
 
 To return to the observations, it is not clear from 
 
Changes and Floods on Mars 53 
 
 the record whether the southern extension of the 
 Northern Sea was blue or gray. It was merely re- 
 corded and drawn "as dark as the Northern Sea." 
 On July 24 Mr. Douglass also recorded a large 
 southern dark spot which appeared to him as dark as 
 the Northern Sea, but which I had not noticed upon 
 the 23d. Upon July 25 the original outlines of the 
 Northern Sea were again well seen (Fig. 6), the re- 
 gion south-west of it now being much lighter colored. 
 The southern dark area seen by Mr. Douglass, and 
 of which he had told me, was also noted. As a whole 
 this area was not now as dark as the Northern Sea, 
 but it contained a smaller spot which seemed quite 
 as dark. There was also a narrow white channel 
 extending northwards from the snow. The eastern 
 arm of the Y, formerly so wide, was now reduced to 
 a mere thread, while a trace of the central arm was 
 again visible. 
 
 The Y is now so placed that it is only visible to 
 the observatories to the west of us, and we shall not 
 be able to observe it again until the middle of Au- 
 gust. A striking difference may be noted in the ar- 
 rangement of the dark channels in figures 3 and 4. 
 In both instances they were well seen, and carefully 
 drawn, and I do not see how the difference could be 
 due to an error. The latter arrangement was sub- 
 sequently confirmed by two other drawings. Re- 
 garding the former I find the record, "The dark 
 
54) Mars 
 
 parts are usually not more than 150 miles broad." 
 I can scarcely think, however, that they could have 
 been as broad as that. 
 
 The central branch of the Y was only noted by 
 me upon one occasion in 1890, and that was upon 
 May 25, when it was extremely faint. The date cor- 
 responding to July 12, 1892, in the previous opposi- 
 tion was August 24, 1890. At that time the Y was 
 not visible in Cambridge. The corresponding date 
 at the next opposition will be May 31, 1894<. If the 
 appearance of this central branch is in any way 
 connected with the seasons upon Mars, it will be of 
 interest for those observatories which are favorably 
 situated at that time to look for it, since, should it 
 then be as conspicuous a phenomenon as it has been 
 this year, it could be readily detected by compara- 
 tively small telescopes. 
 
 In seeking to explain these observations, I would 
 merely point out the fact that the changes occurred 
 at a time when the snow was melting with great 
 rapidity, that a dark channel suddenly appeared 
 July 12, which had not been seen at the last pre- 
 vious observation of this region June 13, that it 
 shortly disappeared again, and that a few days 
 after this event the Northern Sea largely increased 
 in area temporarily, or at least that its southern 
 shores became much darker. I think these changes 
 cannot be explained by Arean cloud effects. We 
 
 N, 
 
Changes and Floods on Mars 55 
 
 have already observed large wliitish patches upon 
 the planet, which undergo considerable changes in 
 shape and extent from night to night. We are now 
 studying them carefully, although we find them 
 rather difficult of observation. These changes we 
 are inclined to refer to clouds, although the matter 
 is not so simple as it might at first appear. If 
 these effects are really due to clouds, they are quite 
 different in character from the other changes noted 
 above. 
 
 If the reader is inclined to be surprised at the 
 extraordinary character of the phenomena now ap- 
 parently occurring upon our sister planet, as re- 
 vealed by the telescope, I can assure him that he is 
 no more so than were the observers themselves. Nor 
 do we insist upon any explanation of these changes, 
 but only upon the accuracy of the observations them- 
 selves. Owing to our remote and isolated position, 
 we know nothing at the present writing of what has 
 been done and seen at the northern Observatories, 
 and it is possible that when this strikes the reader's 
 eye, it will not be as new to him as it is now to us. 
 Nevertheless, I am inclined to think that owing to 
 our splendid atmosphere, and southern latitude, por- 
 tions of what precedes may still be new, although 
 the larger northern telescopes will doubtless have 
 detected all the more important changes. 
 
CHAPTER VI 
 MARS IN 1892 ^ 
 
 Now that the opposition of 1892 has passed into 
 history, it may be well to give a brief summary of 
 the observations made at Arequipa this year, pre- 
 paratory to a more complete pubhcation elsewhere. 
 With one exception, the planet has been observed 
 every night continuously, from July 9 until Septem- 
 ber 24, when the lens of the telescope was reversed, 
 for photographic work, and the regular observations 
 came to an end. Since the beginning of the year 
 Mr. Douglass and myself have made 373 drawings 
 of different features of the planet, thirteen of them 
 being colored. Numerous micrometric measure- 
 ments of the equatorial, polar, and phase diameters 
 have been made. A large number of measurements 
 of the snow, and other observations for correcting 
 the physical ephemeris of the planet have been col- 
 lected. Ninety-two stations have been located upon 
 the planet micrometrically, many of them having 
 been observed upon several different dates. Besides 
 
 ' Astronomy and Astro-Fhysics, 1892, 11, 84i9. 
 66 
 
Mars m 1892 57 
 
 these, measurements of the clouds, and the breadths 
 of the lakes, canals, and minor features have been ob- 
 tained. Considerable data has thus been collected 
 at this opposition for future discussion. 
 
 Turning now to what we may call the definite 
 conclusions to be derived from our observations, we 
 may say: — 
 
 I. That the polar caps are clearly distinct in ap- 
 pearance from the cloud formations, and are not to 
 be confounded with them. 
 
 II. That clouds undoubtedly exist upon the planet, 
 differing, however, in some respects from those upon 
 the Earth, chiefly as regards their density and white- 
 ness. 
 
 III. There are two permanently dark regions upon 
 the planet, which under favorable circumstances ap- 
 pear blue, and are presumably due to water. 
 
 IV. Certain other portions of the surface of the 
 planet are undoubtedly subject to gradual changes 
 of color, not to be explained by clouds. 
 
 V. Excepting the two very dark regions referred 
 to above, all of the shaded regions upon the planet 
 have at times a greenish tint. At other times they 
 appear absolutely colorless. Clearly marked green 
 regions are sometimes seen near the poles. 
 
 VI. Numerous so-called canals exist upon the 
 planet, substantially as drawn by Professor Schia- 
 pareUi. Some of them are only a few miles in 
 
58 Mars 
 
 breadth. No striking instances of duplication have 
 been seen at this opposition. 
 
 VII. Through the shaded regions run certain 
 curved branching dark lines. They are too wide 
 for rivers, but may indicate their courses. 
 
 VIII. Scattered over the surface of the planet, 
 chiefly on the side opposite to the two seas, we have 
 found a large number of minute black points. They 
 occur almost without exception at the junctions of 
 the canals with one another, and with the shaded 
 portions of the planet. They range from thirty to 
 one hundred miles in diameter, and in some cases 
 are smaller than the canals in which they are sit- 
 uated. Over forty of them have been discovered, and 
 for convenience we have termed them lakes. 
 
 No repetition of the phenomena connected with 
 the melting snow, which occurred in July has been 
 observed. The Y mark has assumed its customary 
 appearance, so that the narrowing of the southern 
 branch seems to have been a temporary phenom- 
 enon, and was probably due to clouds. The central 
 branch is now continuously visible, but its southern 
 extremity which connected it ^"ith the snow has dis- 
 appeared. The southern branch of the Y also seems 
 to be gradually fading out. 
 
 Clouds have on several occasions been observed to 
 project beyond the terminator, and also beyond the 
 limb, thus confirming the observations made at the 
 
Mars in 1892 59 
 
 Lick Observatory. The height of these clouds has 
 been measured, and it appears that some of them 
 attained an altitude of at least twenty miles, — a 
 height considerably greater than that attained by 
 terrestrial clouds. This is a result naturally to be 
 expected from the small mass of the planet. No 
 direct measures have been possible of the density 
 of the atmosphere at the planet's surface, but in- 
 direct observations lead us to conclude that it is 
 less than that at the surface of the Earth, but prob- 
 ably not as much as ten times less. 
 
 A curious feature of the observations has been the 
 distinct flattening at the planet's poles, amounting 
 to at least ~ . P'rom theoretical considerations, 
 unless we assume a rather improbable internal struc- 
 ture, it cannot exceed ^^, and that is approxi- 
 mately the figure which Professor Young derived 
 from his measurements. Herschel made it i 
 Arago ~, and other observers have obtained vari- 
 ous results, in general greater than ours. The above 
 figure must not be considered by any means final, 
 but merely as an approximate minimum, since our 
 computations have not as yet been completed. That 
 the flattening at opposition was considerable was 
 very evident. As no such conspicuous discrepancies 
 among different observers occur in the case of the 
 other planets, I am inclined to think that the varia- 
 tions may be real, and due perhaps to an equatorial 
 
60 ' Mars 
 
 cloud formation. Clouds are certainly very frequent 
 upon the sunrise terminator, particularly towards 
 the equator. In any case this is an interesting mat- 
 ter for investigation at future oppositions. 
 
 As the snow in melting receded towards the pole, 
 there was a narrow, nearly straight region upon 
 which it lingered longer than elsewhere. At present 
 the snow is divided into two sections, one long and 
 narrow, the other of irregular shape, and some- 
 what mottled. The appearance is such as might be 
 produced by a mountain range and an area of irreg- 
 ular elevation, with a valley lying between them. It 
 was from this supposed valley that the dark line is- 
 sued in July connecting it with the Northern Sea. 
 
 Upon August 5, in the region just to the north 
 of Solis Lacus, latitude — 20°, a small but con- 
 spicuous white spot appeared. It was conspicuous 
 from being brighter than any other spot upon the 
 planet save the southern snow cap, which it exactly 
 resembled in color. 
 
 A similar but much smaller spot was also noticed 
 further to the southwest. Both spots had disap- 
 peared by August 7, but careful measurements upon 
 two nights, an(J several drawings, had already ac- 
 curately located their positions. The larger of these 
 spots measured about 60 miles in length by perhaps 
 40 in width, and was much brighter than any cloud 
 that I have evei seen upon the planet. I am in- 
 
Mars m 1892 61 
 
 clined to attribute both of these spots to snow. We 
 have frequently seen small white points lying along 
 the line which bounds the shaded regions upon the 
 north. Early in August the whole northern edge 
 of the Equatorial Sea was bounded by a narrow 
 white line, while later a similar line bounded the 
 Northern Sea upon the west. These lines were ap- 
 parently due to cloud, and were not as bright as 
 the spots of snow referred to above. Although 
 nearly a thousand miles long, they could hardly have 
 exceeded thirty miles in breadth. 
 
 Although Mars has been nearer the Earth at this 
 past opposition than it will be again for fifteen years, 
 I am quite inclined to believe that it will be better 
 seen in 1894 than it has been this year. My rea- 
 sons for this statement are as follows : — In the first 
 place, its distance from the Earth will not be very 
 much greater than it was this past year, and indeed 
 for part of the time it will be less remote than it 
 was when many of our most interesting observations 
 were secured. Secondly, it will be much farther 
 north, where the great northern telescopes can be 
 used upon it to much greater advantage. Thirdly, 
 following the melting of the southern snow, the 
 Arean atmosphere was filled with clouds, and these 
 did not clear away satisfactorily until the very end 
 of August, or long after the opposition was over. 
 It was only after the clouds began to clear, that the 
 
62 Mars 
 
 Arean lakes, which have proved such an interesting 
 feature of this opposition, began to show to their full 
 advantage. Owing to the change of seasons upon 
 Mars, little of this latter difficulty should be ex- 
 perienced at the next opposition, and it is thought 
 that many lakes and other delicate features still re- 
 main undiscovered, which may reveal themselves at 
 that time. Could the great 40-inch telescope of 
 Southern California then be completed, undoubtedly 
 the best views of the planet would be obtained at that 
 point, but if it is not, the Lick telescope can cer- 
 tainly be used to greater advantage, and the Are- 
 quipa telescope to no less advantage, than was the 
 case this year. 
 
CHAPTER Vn 
 
 SCHIAPARELLI'S LATEST VIEWS REGARD- 
 ING MARS 1 
 
 It is probable that the astronomer whose name is 
 most closely linked with the planet Mars at the 
 present time is Giovanni Schiaparelli. And yet al- 
 though nearly everybody has heard of Schiaparelli's 
 canals, very few astronomers even, outside of France 
 and Italy, had until recently more than a very vague 
 notion what were really his ideas in regard to them. 
 This is due probably to the fact that he has written 
 exclusively in Italian, a language which very few 
 American astronomers, and I believe very few Eng- 
 lish ones, understand. To this fact chiefly I think is 
 due the great incredulity with which his observations 
 have been treated, at least until recently, in both of 
 these countries. Astronomers could understand his 
 maps, they knew therefore what he had done, but 
 they could not understand his description of his 
 observations, and so were incredulous regarding 
 their accuracy. Moreover, such a mass of detail 
 
 ' Astronomy and Astro-Physics, 1894, 13, 632, 714. 
 63 
 
64! Man 
 
 appeared upon his maps, which had not before been 
 seen by others, that it completely masked the more 
 striking features of the planet, thus rendering its 
 appearance entirely different from that which it 
 presented in the telescope under ordinary atmospheric 
 conditions. 
 
 But within the last few years a change has oc- 
 curred. Flammarion has translated a large part of 
 Schiaparelli's writings into French, a language with 
 which most English-speaking astronomers are fa- 
 miliar, and moreover the canals have been seen by a 
 number of astronomers whose descriptions of them 
 in English and French could be understood, and 
 were found to agree with those of Schiaparelli. 
 
 But errors are stiU frequently made by people 
 who might be expected to know better. Thus, many 
 people suppose that Schiaparelli was the original 
 discoverer of canals, a claim which he never made 
 for himself. In point of fact some of them appear 
 upon maps of the planet published more than fifty 
 years ago. The former English incredulity in the 
 matter seems the more strange, since many of the 
 canals were seen by Dawes in 1864, and by Burton 
 and Dreyer in 1879. Schiaparelli however has dis- 
 covered far more canals than anyone else, and he is 
 also the discoverer of their gemination. 
 
 In this connection it may be that a brief chrono- 
 logical statement of the more important facts and 
 
Schiaparelli's Latest Views Regarding Mars 65 
 
 discoveries relating to Mars will not be without 
 interest. In compiling it I have been chiefly indebted 
 to Flammarion's classic work "La Planete Mars," 
 although other sources have also been consulted. 
 
 272 B. c. The first known observation of Mars is 
 recorded in Ptolemy's Almagest. 
 
 1610. The phases of Mars were discovered by 
 Galileo. 
 
 1659. The first sketch showing surface detail was 
 made by Huyghens. He also suggested a rotation 
 in 24 hours. 
 
 1666. Cassini determined the rotation of Mars 
 to take place in 24 hours 40 minutes. He also ob- 
 served the polar caps, and "he distinguished on 
 the disc of Mars, near the terminator, a white spot 
 advancing into the dark portion and representing 
 without doubt, like those of the Moon, a roughness 
 or irregularity of surface." This latter statement 
 is curious, but the effect was undoubtedly due to 
 irradiation, since his telescope was entirely inad- 
 equate to enable him to observe such a delicate 
 phenomenon. 
 
 1777. With the exception of Huyghens, Hooke, 
 and possibly Maraldi, no one succeeded in making 
 recognizable sketches of the surface detail upon 
 Mars for over a century, until Sir William Herschel 
 took the matter up this year. 
 
 1783. Sir William Herschel detected the varia- 
 
66 Mars 
 
 tion of the size of the polar snow caps with the 
 seasons, measured the polar compression, and deter- 
 mined the inclination of the axis of the planet to 
 its orbit. 
 
 1785-1802. Schroeter made an extended study of 
 the planet. His drawings are upon the whole rather 
 better than those of Herschel. He discovered among 
 other things the very dark spots to which I have 
 referred in my publications as the Northern and 
 Equatorial Seas. He, however, supposed them to be 
 clouds. 
 
 1840. Beer and Maedler published the first map 
 of the planet assigning latitudes and longitudes to 
 the various markings. On this map are indicated the 
 first canals, and the first of the small lakes, so many 
 of which have been discovered during the last few 
 years. The canals are Nectar and Agathodaemon 
 and portions of Hades and Tartarus. The lake is 
 Lacus Phoenicis. Their map is the first satisfactory 
 representation of the entire surface of the planet. 
 The only region which previous observers had 
 clearly distinguished was that in the vicinity of the 
 Syrtis Major. 
 
 1858. Secchi made a careful study of the colors 
 exhibited by the planet. 
 
 1862. Lockyer made the first series of really 
 good sektches of the planet, showing all the charac- 
 teristic forms with which we are now so famiHar. 
 
SchiaparelU's Latest Views Regarding Mars 67 
 
 His drawings, and also those of some of the other 
 observers, give the first indications of the appear- 
 ance of the central branch in the Y, so called by 
 Secchi. 
 
 1864. Dawes detected eight or ten of the canals. 
 
 1867. Huggins detected lines due to the presence 
 of water vapor in the spectrum of Mars. 
 
 1867. Proctor determined the period of rotation 
 of Mars within 0.1 second. 
 
 1877. iiaU discovered the two satellites of Mars. 
 
 1877. Green made a very excellent series of 
 drawings of the planet, superior to anything which 
 had preceded them. 
 
 1877. Schiaparelli made the first extensive tri- 
 angulation of the surface of the planet, and added 
 very largely to the number of known canals. 
 
 1879. Schiaparelli detected the gemination of 
 Nilus, — the first known double canal. 
 
 1882. Schiaparelli discovered numerous double 
 canals, and announced that the appearance formed 
 one of the characteristic phenomena of the planet. 
 
 The most reliable confirmation of this phenomenon 
 hitherto reported has come from Perrotin of Nice, 
 and A. Stanley WiUiams in England. If Schiapa- 
 relU's theory is correct, that the duplication occurs 
 only between the spring and autumn equinoxes of 
 the northern hemisphere, the last opportunity to 
 witness it was in 1890, and the next in January and 
 
68 Mart 
 
 February of 1895, unless the planet proves to be 
 too remote at that period. 
 
 Very few of Schiaparelli's writings have ever been 
 translated into English, and none so far as I know, 
 hitherto, without the intervention of some other 
 language, such as German or French. The following 
 translation is from "Natura ed Arte" for February 
 15, 1893. It gives the latest expression of his views 
 upon the periodical inundations experienced by the 
 planet, upon the nature of the seas, the canals, and 
 the gemination of the latter. 
 
 THE PLANET MARS 
 
 GIOVANNI SCHIAPAEELLI 
 
 Many of the first astronomers who studied Mars 
 with the telescope, had noted on the outline of its 
 disc two brilliant white spots of rounded form and 
 of variable size. In process of time it was observed 
 that whilst the ordinary spots upon Mars were dis- 
 placed rapidly in consequence of its daily rotation, 
 changing in a few hours both their position and 
 their perspective, that the two white spots remained 
 sensibly motionless at their posts. It was concluded 
 rightly from this, that they must occupy the poles 
 of rotation of the planet, or at least must be found 
 very near to them. Consequently they were given 
 the name of polar caps or spots. And not without 
 
SchiapareUi's Latest Views Regarding Mars 69 
 
 reason is it conjectured, that these represent upon 
 Mars that immense mass of snow and ice, which 
 still today prevents navigators from reaching the 
 poles of the Earth. We are led to this conclusion 
 not only by the analogy of aspect and of place, but 
 also by another important observation. 
 
 flr vp flt ip vp ip flt V 
 
 As things stand, it is manifest, that if the above 
 mentioned white polar spots of Mars represent snow 
 and ice, they should continue to decrease in size 
 with the approach of summer in those places, and 
 increase during the winter. Now this very fact is 
 observed in the most evident manner. In the second 
 half of the year 1892 the southern polar cap was 
 in full view; during that interval, and especially in 
 the months of July and August, its rapid diminu- 
 tion from week to week was very evident, even to 
 those observing with common telescopes. This snow, 
 (for we may well call it so,) which in the beginning 
 reached as far as latitude 70°, and formed a cap 
 of over 2,000 kilometers (1,200 miles) in diameter, 
 progressively diminished, so that two or three months 
 later little more of it remained than an area of 
 perhaps 300 kilometers, (180 miles) at the most, 
 and still less was seen later in the last days of 1892. 
 In these months the southern hemisphere of Mars 
 had its summer ; the summer solstice occurring upon 
 
70 Mars 
 
 October 13. Correspondingly the mass of snow 
 surrounding the northern pole should have increased ; 
 but this fact was not observable, since that pole 
 was situated in the hemisphere of Mars which was 
 opposite to that facing the Earth. The melting of 
 the northern snow was seen in its turn in the years 
 1882, 1884. and 1886. 
 
 These observations of the alternate increase and 
 decrease of the polar snows are easUy made, even 
 with telescopes of moderate power, but they become 
 much more interesting and instructive when we can 
 foUow assiduously the changes in their more minute 
 particulars, using larger instruments. The snowy 
 regions are then seen to be successively notched at 
 their edges ; black holes and huge fissures are formed 
 in their interiors ; great isolated pieces many miles 
 in extent stand out from the principal mass, and 
 dissolving disappear a Uttle later. In short, the 
 same divisions and movements of these icy fields 
 present themselves to us, at a glance, that occur 
 during the summer of our own arctic regions, ac- 
 cording to the descriptions of explorers. 
 
 The southern snow, however, presents this pecu- 
 Uarity, that the center of its irregularly rounded 
 figure does not coincide exactly with the pole, but 
 is situated at another point, which is nearly always 
 the same, and is distant from the pole about 300 
 kilometers (180 miles) in the direction of the Mare 
 
Schiaparelli's Latest Views Regarding Mars 71 
 
 Erythraeum. From this we conclude that when the 
 area of the snow is reduced to its smallest extent, 
 that the south pole of Mars is uncovered; and 
 therefore perhaps, the problem of reaching it upon 
 tliis planet is easier than upon the Earth. The 
 southern snow is in the midst of a huge dark spot, 
 which with its branches occupies nearly one-third 
 of the whole surface of Mars, and is supposed to 
 represent its principal ocean. Hence the analogy 
 with our arctic and antarctic snows may be said to 
 be complete, and especially so with the antarctic one. 
 The mass of the northern snow-cap of Mars is on 
 the other hand centered almost exactly upon its 
 pole. It is located in a region of yellow color, which 
 we are accustomed to consider as representing the 
 continent of the planet. From this arises a singular 
 phenomenon which has no analogy upon the Earth. 
 At the melting of the snows, accumulated at that 
 pole during the long night of ten months and more, 
 the liquid mass produced in that operation is dif- 
 fused around the circumference of the snowy region, 
 converting a large zone of surrounding land into a 
 temporary sea, and filling aU the lower regions. 
 This produces a gigantic inundation, which has led 
 some observers to suppose the existence of another 
 ocean in those parts, but which does not really exist 
 in that place, at least as a permanent sea. We see 
 then, (the last opportunity was in 1884), the white 
 
72 Mars 
 
 spot of the snow surrounded by a dark zone, which 
 follows its perimeter ia its progressive dimiuution, 
 upon a circumference ever more and more narrow. 
 The outer part of this zone branches out into dark 
 lines which occupy all the surrounding region, and 
 seem to be distributary canals, by which the liquid 
 mass may return to its natural position. This pro- 
 duces in these regions very extensive lakes, such as 
 that designated upon the map by the name of Lacus 
 Hyperboreus ; the neighboring interior sea called 
 Mare AcidaHum becomes more black, and more con- 
 spicuous. And it is to be remembered as a very 
 probable thing, that the flowing of this melted 
 snow is the cause which determines principally the 
 hydrographic state of the planet, and the variations 
 that are periodically observed ia its aspect. Some- 
 thing similar would be seen upon the Earth, if one 
 of our poles came to be located suddenly in the cen- 
 ter of Asia or Africa. As things stand at present, 
 we may find a miniature image of these conditions in 
 the flooding that is observed in our streams at the 
 melting of the Alpine snows. 
 
 Travellers in the arctic regions have frequent 
 occasion to observe how the state of the polar ice 
 at the beginning of the summer, and even at the 
 beginning of July is always very unfavorable to 
 their progress. The best season for exploration is 
 in the month of August, and September is the month 
 
SchiaparelU's Latest Views Regarding Mars 73 
 
 in which the trouble from the ice is the least. Thus 
 in September our Alps are usually more practicable 
 than at any other season. And the reason for it is 
 clear, the melting of the snow requires time, a high 
 temperature is not sufficient, it is necessary that it 
 should continue, and its effect will be so much the 
 greater, as it is the more prolonged. Thus, if we 
 could slow down the course of our seasons, so that 
 each month should last sixty days instead of thirty, 
 in the summer in such a lengthened condition, the 
 melting of the ice would progress much further, and 
 perhaps it would not be an exaggeration to say that 
 the polar cap at the end of the warm season would 
 be entirely destroyed. But one cannot doubt in any 
 case, that the fixed portion of such a cap would 
 be reduced to much smaller size than we see it today. 
 Now this is exactly what happens in Mars. The 
 long year, nearly double our own, permits the ice 
 to accumulate during the polar night of ten or twelve 
 months, so as to descend in the form of a continuous 
 layer as far as parallel 70°, or even further. But 
 in the day which follows of twelve months or ten 
 months, the Sun has time to melt all or nearly all, 
 of the snow of recent formation, reducing it to such 
 a small area, that it seems to us no more than a 
 very white point. And perhaps this snow is entirely 
 destroyed, but of this there is at present no satis- 
 factory observation. 
 
74 Mars 
 
 Other white spots of a transitory character, and 
 of a less regular arrangement are formed in the 
 southern hemisphere, upon the islands near the pole, 
 and also in the opposite hemisphere, whitish regions 
 appear at times surrounding the north pole, and 
 reaching to 50° and 55° of latitude. They are per- 
 haps transitory snows, similar to those which are 
 observed in our latitudes. But also in the torrid 
 zone of Mars are seen some very small white spots 
 more or less persistent, amongst others one was seen 
 by me in three consecutive oppositions (1877-1882) 
 at the point indicated upon our chart by longitude 
 268° and latitude 16° north. Perhaps we may be 
 permitted to imagine in this place the existence of 
 a mountain capable of supporting extensive ice- 
 fields. The existence of such a mountain has been 
 supposed also by some recent observers, founded 
 upon other facts. 
 
 As has been stated, the polar snows of Mars prove 
 in an incontrovertible manner, that this planet, like 
 the Earth, is surrounded by an atmosphere capable 
 of transporting vapor from one place to another. 
 These snows are in fact precipitations of vapor, 
 condensed by the cold, and carried with it succes- 
 sively. How carried with it, if not by atmospheric 
 movement.? The existence of an atmosphere charged 
 with vapor has been confirmed also by spectroscopic 
 observations, principally those of Vogel; according 
 
Schiaparelli's Latest Views Regarding Mars 75 
 
 to which this atmosphere must be of a composition 
 differing little from our own, and above all very 
 rich in aqueous vapor. This is a fact of the highest 
 importance, because from it we can rightly afBrm 
 with much probability, that to water, and to no 
 other liquid is due the seas of Mars and its polar 
 snows. When this conclusion is assured beyond all 
 doubt, another one may be derived from it, of not 
 less importance, — that the temperature of the Arean 
 climate, notwithstanding the greater distance of that 
 planet from the Sun, is of the same order as the 
 temperature of the terrestrial one. Because, if it 
 were true, as has been supposed by some investi- 
 gators, that the temperature of Mars was on the 
 average very low (from 50° to 60° below zero) it 
 would not be possible for water vapor to be an im- 
 portant element in the atmosphere of that planet, 
 nor could water be an important factor in its 
 physical changes ; but would give place to carbonic 
 acid, or to some other liquid whose freezing point 
 was much lower. 
 
 The elements of the meteorology of Mars seem 
 then to have a close analogy to those of the Earth. 
 But there are not lacking, as might be expected, 
 causes of dissimilarity. From circumstances of the 
 smallest moment, nature brings forth an infinite 
 variety in its operations. Of the greatest influence 
 must be the different arrangement of the seas and 
 
76 Mars 
 
 the continents upon Mars, and upon the Earth, 
 regarding which, a glance at the map will say more 
 than would be possible in many words. We have 
 already emphasized the fact of the extraordinary 
 periodical flood, which at every revolution of Mars 
 inundates the northern polar region at the melting 
 of the snow. Let us now add that this inundation is 
 spread out to a great distance by means of a net- 
 work of canals, perhaps constituting the principal 
 mechanism (if not the only one) by which water 
 (and with it organic life) may be diffused over the 
 arid surface of the planet. Because on Mars it rains 
 very rarely, or perhaps even, it does not rain at 
 all. And this is the proof. 
 
 Let us carry ourselves in imagination into celes- 
 tial space, to a point so distant from the Earth, that 
 we may embrace it aU at a single glance. He would 
 be greatly in error who had expected to see repro- 
 duced there, upon a great scale, the image of our 
 continents, with their gulfs and islands, and with the 
 seas that surroiuid them, wliich are seen upon our 
 artificial globes. There without doubt the known 
 forms, or part of them, would be seen to appear 
 under a vaporous veil, but a great part (perhaps 
 one-half) of the surface would be rendered invisible 
 by the immense fields of cloud, continually varying 
 in density, in form and in extent. Such a hindrance, 
 most frequent and continuous in the polar regions, 
 
Schiaparelli'i Latett View* Regarding Mart 77 
 
 would still impede nearly half the time the view of 
 the temperate zones, distributing itseK in capricious 
 and ever varying configurations. The seas of the 
 torrid zone would be seen to be arranged in long 
 parallel layers, corresponding to the zone of equa- 
 torial and tropical calms. For an observer placed 
 upon the Moon, the study of our geography would 
 not be so simple an undertaking as one might at first 
 imagine. 
 
 There is nothing of this sort in Mars. In every 
 climate, and under every zone, its atmosphere is 
 nearly perpetually clear, and sufficiently transparent 
 to permit one to recognize at any moment whatever, 
 the contours of the seas and continents, and more 
 than that, even the minor configurations. Not in- 
 deed that vapors of a certain degree of opacity are 
 lacking, but they offer very little impediment to 
 the study of the topography of the planet. Here 
 and there we see appear from time to time a few 
 whitish spots changing their position and form, 
 rarely extending over a very wide area. They fre- 
 quent by preference a few regions, such as the islands 
 of the Mare Australe, and on the continents, the 
 regions designated on the map with the names of 
 Elysium and Tempe. Their brilliancy generally di- 
 minishes and disappears at the meridian hour of the 
 place, and is reinforced in the morning and even- 
 ing, with very marked variations. It is possible that 
 
78 Mars 
 
 they may be layers of cloud, because the upper por- 
 tions of terrestrial clouds, where they are illuminated 
 by the Sun, appear white. But various observa- 
 tions lead us to think that we are dealing rather with 
 a thin veil of fog, instead of a true nimbus cloud, 
 carrying storms and rain. Indeed it may be merely 
 a temporary condensation of vapor, under the form 
 of dew or hoar frost. 
 
 Accordingly, as far as we may be permitted to 
 argue from the observed facts, the climate of Mars 
 must resemble that of a clear day upon a high moun- 
 tain. By day a very strong solar radiation hardly 
 mitigated at aU by mist or vapor, by night a copious 
 radiation from the soil towards celestial space, and 
 because of that a very marked refrigeration. Hence 
 a climate of extremes, and great changes of temper- 
 ature from day to night, and from one season to 
 another. And as on the Earth at altitudes of 5,000 
 and 6,000 meters (17,000 to 20,000 feet), the vapor 
 of the atmosphere is condensed only into the solid 
 form, producing those whitish masses of suspended 
 crystals, which we call cirrus clouds, so in the at- 
 mosphere of Mars, it would be rarely possible (or 
 would even be impossible) to find collections of cloud 
 capable of producing rain of any consequence. The 
 variation of the temperature from one season to an- 
 other would be notably increased by their long dura- 
 tion, and thus we can understand the great freezing 
 
SchiaparelU's Latest Vieu-s Regarding Mars 79 
 
 and melting of the snow, -which is renewed in turn at 
 the poles at each complete revolution of the planet 
 around the Sun. 
 
 As our chart demonstrates, in its general topog- 
 raphy Mars does not present any analogy with the 
 Earth. A third of the surface is occupied by the 
 great !Mare Australe, which is strewn with many is- 
 lands, and the continents are cut up by gulfs and 
 ramifications of various forms. To the general wa- 
 ter system belongs an entire series of small internal 
 seas, of which the Hadriacum and the Tyrrhenum 
 communicate with it by wide mouths, whilst the Cim- 
 merium, the Sirenum and the Solis Lacus are con- 
 nected with it only by means of narrow canals. We 
 shall notice in the first four a parallel arrangement, 
 which certainly is not accidental, as also not with- 
 out reason is the corresponding position of the pe- 
 ninsulas of Ausonia, Hesperia and Atlantis. The 
 color of the seas of Mars is generally brown, mixed 
 with grey, but not always of equal intensity in all 
 places, nor is it the same in the same place at all 
 times. From an absolute black it may descend to 
 a light gray, or to an ash color. Such a diversity 
 of colors may have its origin in various causes, and 
 is not without analogy also upon the Earth, where 
 it is noted that the seas of the warm zone are usually 
 much darker than those nearer the pole. The water 
 of the Baltic, for example, has a light, muddy color, 
 
80 Mart 
 
 that is not observed in the Mediterranean. And thus 
 in the seas of Mars, we see the color become darker 
 when the Sun approaches their zenith, and summer 
 begins to rule in that region. 
 
 All of the remainder of the planet, as far as the 
 north pole, is occupied by the mass of the conti- 
 nents, in which, save in a few areas of relatively 
 small extent, an orange color predominates, which 
 sometimes reaches a dark red tint, and in others de- 
 scends to yellow and white. The variety in this 
 coloring is in part of meteorological origin, in part 
 it may depend on the diverse nature of the soil, but 
 upon its real cause it is not as yet possible to frame 
 any very well grounded hypothesis. Nevertheless, 
 the cause of this predominance of the red and yeUow 
 tints upon the surface of ancient Pyrois is well 
 known. ^ Some have thought to attribute this color- 
 ing to the atmosphere of Mars, through which the 
 surface of the planet might be seen colored, as any 
 terrestrial object becomes red, when seen through 
 red glass. But many facts are opposed to this idea, 
 among others, that the polar snows appear always 
 of the purest white, although the rays of light de- 
 rived from them traverse twice the atmosphere of 
 Mars under great obliquity. We must then con- 
 
 ' Pyrois I take to be some terrestrial region, although I have 
 not been able to find any translation of the name. — Tr. 
 
Schiaparelli's Latest Views Regarding Mars 81 
 
 elude that the Arean continents appear red and yel- 
 low, because they are so in fact. 
 
 Besides these dark and light regions, which we 
 have described as seas and continents, and of whose 
 nature there is at present scarcely left any room 
 for doubt, some others exist, truly of small extent, 
 of an amphibious nature, which sometimes appear 
 yellowish like the continents, and are somietimes 
 clothed in brown (even black in certain cases) and 
 assume the appearance of seas, whilst in other cases 
 their color is intermediate in tint, and leaves us in 
 doubt to which class of regions they may belong. 
 Thus all the islands scattered through the Mare 
 Australe and the Mare Erythraeum belong to this 
 category, so too the long peninsulas called Deuca- 
 lionis Regio and Pyrrhae Regio, and in the vicinity 
 of the Mare Acidalium the regions designated by the 
 names of Baltia and Nerigos. The most natural idea, 
 and the one to which we should be led by analogy, is 
 to suppose these regions to represent huge swamps, in 
 which the variation in depth of the water produces 
 the diversity of colors. Yellow would predominate 
 in those parts where the depth of the liquid layer 
 was reduced to little or nothing, and brown, more or 
 less dark, in these places where the water was suffi- 
 ciently deep to abosrb more light, and to render the 
 bottom more or less invisible. That the water of the 
 sea, or any other deep and transparent water, seen 
 
82 Mars 
 
 from above, appears more dark the greater the depth 
 of the liquid stratum, and that the land in compari- 
 son with it appears bright under the solar illumi- 
 nation, is known and confirmed by certain physical 
 reasons. The traveller in the Alps often has occa- 
 sion to convince himself of it, seeing from the sum- 
 mits, the deep lakes with which the region is strewn, 
 extending under his feet as black as ink, whilst in 
 contrast with them even the blackest rocks iLlumiaed 
 by the sunlight appear briUiant.^ 
 
 Not without reason then have we hitherto attrib- 
 uted to the dark spots of Mars the part of seas, and 
 that of continents to the reddish areas which occupy 
 nearly two-thirds of all the planet, and we shall find 
 later, other reasons which confirm this method of 
 reasoning. The continents form in the northern 
 hemisphere a nearly continuous mass, the only im- 
 portant exception being the great lake called the 
 Mare Acidalium, of which the extent may vary ac- 
 cording to the time, and which is connected in some 
 way with the inundations which we have said were 
 produced by the melting of the snow surrounding the 
 north pole. 
 
 To the system of the Mare Acidalium undoubt- 
 
 ' This observation of the dark color which deep water ex- 
 hibits when seen from above, is found already noted by the 
 first author of antique memory, for in the Iliad (verses 770-1 
 of book V) it is described how "the sentinel from the high 
 sentry-box extends his glance over the wine-colored sea." In 
 the version of Monti the adjective indicating the color is lost. 
 
SchiapareUi's Latest Views Regarding Mars 83 
 
 edly belong the temporary lakes called Lacus Hyper- 
 boreus and the Lacus Niliacus. This last is ordi- 
 narily separated from the Mare Acidalium by means 
 of an isthmus or regular dam, of which the continu- 
 ity was only seen to be broken once for a short time 
 in 1888. Other smaller dark spots are found here 
 and there in the continental area, which we may 
 designate as lakes, but they are certainly not perma- 
 nent lakes like ours, but are variable in appearance 
 and size according to the seasons, to the point of 
 whoUy disappearing under certain circumstances. 
 Ismenius Lacus, Lunae Lacus, Trivium Charontis 
 and Propontis are the most conspicuous and durable 
 ones. There are also smaller ones, such as Lacus 
 Moeris and Fons Juventae which at their maximum 
 size do not exceed 100 to 150 kilometers (60 to 90 
 miles) in diameter, and are among the most difficult 
 objects upon the planet. 
 
 All the vast extent of the continents is furrowed 
 upon every side by a network of numerous lines or 
 fine stripes of a more or less pronounced dark color 
 whose aspect is very variable. These traverse the 
 planet for long distances in regular lines, that do 
 not at all resemble the winding courses of our 
 streams. Some of the shorter ones do not reach 500 
 kilometers (300 miles), others on the other hand ex- 
 tend for many thousands, occupying a quarter or 
 sometimes even a third of a circumference of the 
 
84 Mart 
 
 planet. Some of these are very easy to see, espe- 
 cially that one which is near the extreme left-hand 
 limit of our map, and is designated by the name of 
 Nilosyrtis. Others in turn are extremely difficult, 
 and resemble the finest thread of spider's web drawn 
 across the disc. They are subject also to great 
 variations in their breadth, which may reach 200 or 
 even 300 kilometers (120 to 180 miles) for the 
 Nilosyrtis, whilst some are scarcely 30 kilometers 
 (18 miles) broad. 
 
 These lines or stripes are the famous canals of 
 Mars, of which so much has been said. As far as 
 we have been able to observe them hitherto, they are 
 certainly fixed configurations upon the planet. The 
 Nilosyrtis has been seen in that place for nearly one 
 hundred years, and some of the others for at least 
 thirty years. Their length and arrangement are 
 constant, or vary only between very narrow limits. 
 Each of them always begins and ends between the 
 same regions. But their appearance and their de- 
 gree of visibility vary greatly, for all of them, from 
 one opposition to another, and even from one week 
 to another, and these variations do not take place 
 simultaneously and according to the same laws for 
 all, but in most cases happen apparently capricious- 
 ly, or at least according to laws not sufficiently 
 simple for us to be able to unravel. Often one or 
 more become indistinct, or even wholly invisible, 
 
SchiaparelU's Latest Views Regarding Mars 85 
 
 whilst others in their vicinity increase to the point 
 of becoming conspicuous even in telescopes of mod- 
 erate power. The first of our maps shows all those 
 that have been seen in a long series of observations. 
 This does not at all correspond to the appearance of 
 Mars at any given period, because generally only a 
 few are visible at once.* 
 
 Every canal (for now we shall so call them) opens 
 at its end either into a sea, or into a lake, or into 
 another canal, or else into the intersection of several 
 other canals. None of them have yet been seen cut 
 off in the middle of the continent, remaining with- 
 out beginning or without end. This fact is of the 
 highest importance. 
 
 The canals may intersect among themselves at all 
 possible angles, but by preference they converge to- 
 
 ' In a footnote the author refers to a drawing of Mars made 
 by himself, September IS, 1892, and says ". . .At the top of 
 the disc the Mare Erythraeum and the Mare Australe appear 
 divided by a great curved peninsula, shaped like a sickle, pro- 
 ducing an unusual appearance in the area called Deucalionis 
 Regio, which was prolonged that year so as to reach the islands 
 of Noachis and Argyre. This region forms with them a con- 
 tinuous whole, but with faint traces of separation occurring 
 here and there in a length of nearly 6,000 kilometers (4,000 
 miles). Its color, much less brilliant than that of the con- 
 tinents, was a mixture of their yellow with the brownish grey 
 of the neighboring seas." The interesting feature of this note 
 is the remark that it was an unusual appearance, the region 
 referred to being that in which the central branch of the fork 
 of the Y appeared. Since no such branch was conspicuously 
 visible this year, it would therefore seem, from the above, 
 that it was the opposition of 1892 that was peculiar, and not 
 the present one. — Tr. 
 
86 Mars 
 
 wards the small spots to which we have given the 
 name of lakes. For example, seven are seen to con- 
 verge in Lacus Phoenicis, eight in Trivium Charontis, 
 six in Lunae Lacus and six in Ismenius Lacus. 
 
 The normal appearance of a canal is that of a 
 nearly uniform stripe, black, or at least of a dark 
 color, similar to that of the seas, in which the regu- 
 larity of its general course does not exclude small 
 variations in its breadth, and small sinuosities in its 
 two sides. Often it happens that such a dark line 
 opening out upon the sea is enlarged into the form of 
 a trumpet, forming a huge bay, similar to the estu- 
 aries of certain terrestrial streams. The Margariti- 
 fer Sinus, the Aonius Sinus, the Aurorae Sinus, and 
 the two horns of the Sabaeus Sinus are thus formed, 
 at the mouths of one or more canals, opening into 
 the Mare Erythraeum or into the Mare Australe. 
 The largest example of such a gulf is the Syrtis 
 Major, formed by the vast mouth of the NUosyrtis, 
 so called. This gulf is not less than 1,800 kilometers 
 (1,100 miles) in breadth, and attains nearly the 
 same extent in a longitudinal direction. Its surface 
 is little less than that of the Bay of Bengal. In this 
 case we see clearly the dark surface of the sea con- 
 tinued without apparent interruption into that of 
 the canal. In as much as the surfaces called seas 
 are truly a liquid expanse, we cannot doubt that the 
 
Schiaparelli's Latest Views Regarding Mars 87 
 
 canals are a simple prolongation of them, crossing 
 the yeUow areas or continents. 
 
 Of the remainder, that the lines called canals are 
 truly great furrows or depressions in the surface of 
 the planet, destined for the passage of the liquid 
 mass, and constituting for it a true hydrographic 
 system, is demonstrated by the phenomena which are 
 observed during the melting of the northern snows. 
 We have already remarked that at the time of melt- 
 ing they appeared surrounded by a dark zone, form- 
 ing a species of temporary sea. At that time the 
 canals of the surrounding region become blacker and 
 wider, increasing to the point of converting, at a 
 certain time, all of the yellow region comprised be- 
 tween the edge of the snow and the parallel of 60° 
 north latitude, into numerous islands of small ex- 
 tent. Such a state of things does not cease, until 
 the snow, reduced to its minimum area, ceases to 
 melt. Then the breadth of the canals diminishes, the 
 temporary sea disappears, and the yellow region 
 again returns to its former area. The different 
 phases of these vast phenomena are renewed at each 
 return of the seasons, and we have been able to ob- 
 serve them in aU their particulars very easily during 
 the oppositions of 1882, 1884 and 1886, when the 
 planet presented its northern pole to terrestrial 
 spectators. The most natural and the most simple 
 interpretation is that to which we have referred, of 
 
88 Mars 
 
 a great iniindation produced by the melting of the 
 snows, — it is entirely logical, and is sustained by evi- 
 dent analogy with terrestrial phenomena. We con- 
 clude therefore that the canals are such in fact, and 
 not only in name. The network formed by these was 
 probably determined in its origin in the geological 
 state of the planet, and has come to be slowly elab- 
 orated in the course of centuries. It is not necessary 
 to suppose them the work of intelligent beings, and 
 notwithstanding the almost geometrical appearance 
 of all of their system, we are now inclined to believe 
 them to be produced by the evolution of the planet, 
 just as on the Earth we have the English Channel 
 and the Channel of Mozambique. 
 
 It would be a problem not less curious than com- 
 plicated and difficult, to study the system of this im- 
 mense stream of water, upon which perhaps depends 
 principally the organic life upon the planet, if or- 
 ganic life is found there. The variations of their 
 appearance demonstrated that this system is not con- 
 stant. When they become displaced, or their out- 
 lines become doubtful and iU defined, it is fair to sup- 
 pose that the water is getting low, or is even en- 
 tirely dried up. Then in place of the canal there 
 remains either nothing, or at most a stripe of yel- 
 lowish color differing little from the surrounding 
 background. Sometimes they take on a nebulous 
 appearance, for which at present it is not possible 
 
SchiaparelU's Latest Views Regardmg Mars 89 
 
 to assign a reason. At other times true enlarge- 
 ments are produced, expanding to 100, 200 or more 
 kilometers (60 to 120 miles) in breadth, and this 
 sometimes happens for canals very far from the 
 north pole, according to laws which are unknown. 
 This has occurred in Hydaspes in 1864, in Simois in 
 1879, in Acheron in 1884, and in Triton in 1888. 
 The diligent and minute study of the transforma- 
 tions of each canal may lead later to a knowledge 
 of the cause of these facts. 
 
 But the most surprising phenomenon pertaining 
 to the canals of Mars is their gemination, which 
 seems to be produced principally in the months which 
 precede, and in those which follow, the great northern 
 inundation, at about the times of the equinoxes. In 
 consequence of a rapid process, which certainly lasts 
 at most a few days, or even perhaps only a few hours, 
 and of which it has not yet been possible to deter- 
 mine the particulars with certainty, a given canal 
 changes its appearance, and is found transformed 
 through all its length, into two lines or uniform 
 stripes, more or less parallel to one another, and 
 which run straight and equal with the exact geo- 
 metrical precision of the two rails of a railroad. 
 But this exact course is the only point of resem- 
 blance with the rails, because in dimensions there is 
 no comparison possible, as it is easy to imagine. 
 The two lines follow very nearly the direction of the 
 
90 Mars 
 
 original canal, and end in the place where it ended. 
 One of these is often superposed as exactly as pos- 
 sible upon the former Hne, the other being drawn 
 anew, but in this case the original line loses all the 
 small irregularities and curvature that it may have 
 originally possessed. But it also happens that both 
 the lines may occupy opposite sides of the former 
 canal, and be located upon entirely new ground. The 
 distance between the two lines differs in different 
 geminations, and varies from 600 kilometers (360 
 miles) and more, down to the smallest limit at which 
 two lines may appear separated in large visual tele- 
 scopes — less than an interval of 50 kilometers (30 
 miles). The breadth of the stripes themselves may 
 range from the limit of visibility, which we may sup- 
 pose to be 30 kilometers (18 mUes), up to more than 
 100 kilometers (60 miles). The color of the two 
 lines varies from black to a light red, wliich can 
 hardly be distinguished from the general yeUow 
 background of the continental surface. The space 
 between is for the most part yellow, but in many 
 cases appears whitish. The gemination is not neces- 
 sarily confined only to the canals, but tends to be 
 produced also in the lakes. Often one of these is 
 seen transformed into two short, broad, dark lines 
 parallel to one another, and traversed by a yellow 
 line. In these cases the gemination is naturally 
 
ScMaparelli's Latest Views Regarding Mars 91 
 
 short, and does not exceed the limits of the original 
 lake. 
 
 The gemination is not shown by all at the same 
 time, but when the season is at hand, it begins to be 
 produced here and there, in an isolated irregular 
 manner, or at least without any easily recognizable 
 order. In many canals (such as the Nilosyrtis, for 
 example) the gemination is lacking entirely, or is 
 scarcely visible. After having lasted for some 
 months, the markings fade out gradually and dis- 
 appear, until another season equally favorable for 
 their formation. Thus it happens that in certain 
 other seasons (especially near the southern solstice 
 of the planet), that few are seen, or even none at all. 
 In different oppositions the gemination of the same 
 canal may present different appearances, as to width, 
 intensity and arrangement of the two stripes, also 
 in some cases the direction of the lines may vary, 
 although by the smallest quantity, but still deviating 
 by a small amount from the canal with which they 
 are directly associated. From this important fact 
 it is immediately understood that the gemination can 
 not be a fixed formation upon the surface of Mars, 
 and of a geographical character like the canals. The 
 second of our maps will give an approximate idea 
 of the appearance which these singular formations 
 present. It contains all the geminations observed 
 
92 Marg 
 
 since 1882 up to the present time. In examining it, 
 it is necessary to bear in mind that not all of these 
 appearances were simultaneous, and consequently 
 that the map does not represent the condition of 
 Mars at any given period, it is only a sort of topo- 
 graphical register of the observations made at dif- 
 ferent times of this phenomenon.^ 
 
 The observation of the gemination is one of the 
 greatest difficulty, and can only be made by an eye 
 well practiced in such work, added to a telescope of 
 accurate construction, and of great power. This 
 explains why it is that it was not seen before 1882. 
 In the ten years that have transpired since that 
 time, it has been seen and described at eight or ten 
 observatories. Nevertheless, some still deny that 
 these phenomena are real, and tax with illusion (or 
 even imposture) those who declare that they have 
 observed it. 
 
 Their singular aspect, and their being drawn with 
 absolute geometrical precision, as if they were the 
 work of rule or compass, has led some to see in them 
 the work of intelligent beings, inhabitants of the 
 planet. I am very careful not to combat this sup- 
 position, which includes nothing impossible. (To mi 
 guardero bene dal combattere questa supposizione, 
 la quale nulla include d'impossible.) But it will be 
 
 ' This map may be found also in "La Planete Mars," by 
 Flammarion, p. 440. — Tr. 
 
SchiaparelU't Latett Views Regarding Mart 9S 
 
 noticed that in any case the gemination cannot be 
 a work of permanent character, it being certain that 
 in a given instance it may change its appearance and 
 dimensions from one season to another. If we should 
 assume such a work, a certain variabiUty would not 
 be excluded from it, for example, extensive agricul- 
 tural labor and irrigation upon a large scale. Let 
 us add further that the intervention of intelligent 
 beings might explain the geometrical appearance of 
 the gemination, but it is not at all necessary for 
 such a purpose. The geometry of nature is mani- 
 fested in many other facts, from which are excluded 
 the idea of any artificial labor whatever. The per- 
 fect spheroids of the heavenly bodies and the ring 
 of Saturn were not constructed in a turning lathe, 
 and not with compasses has Iris described within the 
 clouds her beautiful and regular arch. And what 
 shall we say of the infinite variety of those exquisite 
 and regular polyhedrons in which the world of crys- 
 tals is so rich ! In the organic world, also, is not 
 that geometry most wonderful which presides over 
 the distribution of the foliage upon certain plants, 
 which orders the nearly symmetrical, starlike figures 
 of the flowers of the field, as well as of the animals 
 of the sea, and which produces in the shell such an 
 exquisite conical spiral, that excels the most beau- 
 tiful masterpieces of gothic architecture? In all 
 these objects the geometrical form is the simple and 
 
94 Mars 
 
 necessary consequence of the principles and laws 
 which govern the physical and physiological world. 
 That these principles and these laws are but an indi- 
 cation of a higher intelligent power, we may admit, 
 but this has nothing to do with the present argu- 
 ment. 
 
 Having regard then to the principle that in the 
 explanation of natural phenomena it is universally 
 agreed to begin with the simplest suppositions, the 
 first hypotheses on the nature and cause of the gemi- 
 nations have for the most part put in operation only 
 the laws of inorganic nature. Thus, the gemination 
 is supposed to be due either to the effects of light 
 in the atmosphere of Mars, or to optical illusions 
 produced by vapors in various manners, or to glacial 
 phenomena of a perpetual winter, to which it is 
 known all the planets will be condemned, or to 
 double cracks in its surface, or to single cracks of 
 which the images are doubled by the effect of smoke 
 issuing in long lines and blown laterally by the wind. 
 The examination of these ingenious suppositions 
 leads us to conclude that none of them seem to corre- 
 spond entirely with the observed facts, either in whole 
 or in part. Some of these hypotheses would not have 
 been proposed, had their authors been able to ex- 
 amine the geminations with their own eyes. Since 
 some of these may ask me directly, — Can you sug- 
 gest anything better.'' I must reply candidly. No. 
 
SchiaparelU's Latest Views Regarding Mars 95 
 
 It would be far more easy if we were willing to 
 introduce the forces pertaining to organic nature. 
 Here the field of plausible supposition is immense, 
 being capable of making an infinite number of com- 
 binations capable of satisfying the appearances even 
 with the smallest and simplest means. Changes of 
 vegetation over a vast area, and the production of 
 animals, also very small, but in enormous multitudes, 
 may well be rendered visible at such a distance. An 
 observer placed in the Moon would be able to see 
 such an appearance at the times in which agricul- 
 tural operations are carried out upon a vaSt plain, 
 — the seed time and the gathering of the harvest. 
 In such a manner also would the flowers of the plants 
 of the great steppes of Europe and Asia be rendered 
 visible at the distance of Mars, — by a variety of 
 coloring. A similar system of operations produced 
 in that planet maj' thus certainly be rendered visible 
 to us. But how difficult for the Lunarians and the 
 Areans to be able to imagine the true causes of 
 such changes of appearance, without having first at 
 least some superficial knowledge of terrestrial na- 
 ture ! So also for us, who know so little of the 
 physical state of Mars, and nothing of its organic 
 world, the great liberty of possible supposition ren- 
 ders arbitrary all explanations of this sort, and con- 
 stitutes the gravest obstacle to the acquisition of 
 well-founded notions. All that we may hope is that 
 
96 Mart 
 
 with time the uncertainty of the problem will grad- 
 ually diminish, demonstrating, if not what the gemi- 
 nations are, at least what they can not be. We may 
 also confide a little in what Galileo called "the cour- 
 tesy of Nature," thanks to which, some time from 
 an unexpected source, a ray of light wiU illuminate 
 an investigation at first beheved inaccessible to our 
 speculations, and of which we have a beautiful ex- 
 ample in celestial chemistry. Let us therefore hope 
 and study. 
 
CHAPTER VIII 
 
 THE SEAS OF MARS i 
 
 The first observation made upon Mars at the 
 Lowell Observatory with the 18-inch Brashear lens 
 was upon June 1, 1894. Since then observations 
 have been continued upon nearly every night. What 
 appears to me to be the most important conclusion 
 deducible from our work so far is that Mars does 
 not always present the same appearance at the cor- 
 responding time upon two successive Arean years. 
 This remark does not apply merely to small details 
 but to large and promijient features. Moreover 
 this difference does not seem to be due simply to 
 the fact that one season is a few weeks later than 
 the other, but that the phenomena presented upon 
 the two years are really different. 
 
 Thus the central branch of the Yf , just north of 
 Noachis, which was so marked a phenomenon in 
 1892, was not visible to me early in June, as I had 
 expected it to be. It is true that Mr. Lowell thought 
 he saw it faintly marked, but although I looked for 
 
 '■ Astronomy and Astro-Physics, 1894, 13, 553. 
 ■j-Syrtis Major. 
 
 97 
 
98 Mars 
 
 it upon the same evening, I could not satisfy myself 
 of its existence. Nevertheless the definition was such 
 that had it appeared as it did in 1892, it could not 
 have been missed at the first glance. I looked for it 
 again at the following presentation in July just 
 passed, but no trace of it was to be seen. Two draw- 
 ings made by Professor Campbell upon July 18 
 and 20, 1892, and published in the last number of 
 the PubUcations of the Astron. Soc. of the Pacific, 
 p. 171, show it very nicely indeed. These may be 
 compared with some reproductions of my own work 
 originally published in Astronomy and Astro- 
 Physics, 1892, p. 668, and now republished in the 
 same number with the drawings of Professor Camp- 
 bell. After the disappearance of the central branch 
 in the latter part of July, 1892, a portion of it re- 
 appeared in August, and remained visible through 
 September. A sketch showing its appearance upon 
 September 4, 1892, has been kindly forwarded to 
 me by Mr. Russell of the Sydney Observatory, 
 N. S. W. This branch may therefore be said 
 to have been characteristic of the opposition of 
 1892. This same region was very carefully sketched 
 by Mr. Douglass and myseK a number of times 
 between June 30 and July 6, 1894, but not a trace 
 of the central branch could we detect. Upon these 
 dates Mars held the same position in its orbit 
 that it did upon August 12 and 18, 1892. A sketch 
 
The Seas of Mars 99 
 
 made by myself August 13, 1892, shows the central 
 branch very clearly. It will be interesting to hear 
 if its appearance has been noted this year by the 
 Australian observers, since in their longitude it would 
 have been visible about the middle of June. 
 
 But not only has the central branch of the Y been 
 invisible this year, but the large dark blue patch 
 which it connected with the southern snow cap, 
 and which we called the Northern Sea, has been very 
 much less marked, and much smaller than was the 
 case in 1892. 
 
 Again a large black gulf bounding the melting 
 snow upon the north and situated very nearly due 
 south of Syrtis Minor has been a very striking 
 feature of our observations this year. This gulf was 
 only observed once in 1892, upon July 27, and it was 
 then by no means conspicuous. If these very dark 
 regions are, as we suppose them to be, water, it 
 would then seem that the water which did not reach 
 the northern regions this year has appeared as an 
 excess in the south. 
 
 Upon testing this black region upon June 4, with 
 an Arago polariscope, made for me by Mr. Brash- 
 ear, it was found to show clear traces of polarization, 
 as did the canal running north from it. This would 
 naturally be the case if it were water, since being 
 situated near the limb, it would reflect to us largely 
 the light of the Arean atmosphere. Upon the rest 
 
100 Mars 
 
 of the disc of the planet the polarization was not 
 very conspicuous. At the next presentation of this 
 region upon July 9, the observation was repeated, 
 but to my surprise no trace of polarization in the 
 dark spot could be detected. A close examination 
 of the region was then made, and its color found to 
 have entirely changed, — whereas upon June 9, Mr. 
 Lowell writes "Bay a deep blue, looks just as deep 
 water does," it was now found to be of a rich choc- 
 olate brown tint, differing entirely in color from 
 the bluish gray regions to the north of it. These 
 gray regions showed no sign of polarization, and as 
 I have before remarked I see no reason for supposing 
 that their color is due to water. As far as my ob- 
 servations go, it appears to me that the permanent 
 water area upon Mars, if it exists at all, is extremely 
 limited in its dimensions. 
 
 These large gray regions were of a brilliant and 
 decided green color in 1890, just before the vernal 
 equinox. In the early part of 1892 also, large green 
 areas were seen upon the planet, but as the season 
 advanced the green regions changed almost entirely 
 to gray. At the present time very little color is 
 visible in the shaded regions. They are subject also 
 to such large variations in area, as the season pro- 
 gresses, that unless we can persuade ourselves that 
 gigantic floods, unaccompanied by clouds, form the 
 normal condition of affairs upon Mars, we seem 
 
The Seas of Mars 101 
 
 forced to adopt some other explanation of their ex- 
 istence. The theory that they owe their color to 
 vegetation is perhaps the most plausible one, and 
 some new facts bearing upon this matter have re- 
 cently come to hand. Upon June 30 a distinct de- 
 pression in the terminator where it was crossed by 
 the stem of the Y was detected by Mr. Douglass. 
 As the planet rotated, the position of the depres- 
 sion changed, and it was noted that it was not 
 always found in those portions of the terminator 
 which were the darkest. Since that date similar 
 depressions more or less marked have been detected 
 upon nearly every evening. Upon looking over our 
 observations for 1892, I find under date of Septem- 
 ber 20, 8h. 06m. a drawing showing a flattened ter- 
 minator, and a statement that "the planet seems 
 somewhat of this shape." Further investigation 
 shows that the long narrow strip known as Cerau- 
 nius was Ij'ing upon the terminator at about this 
 time. These notches in the tenninator can be most 
 readily explained by actual depressions in the sur- 
 face of the planet, and as Professor Campbell has 
 shown (Pub. Astro. Soc. Pac, 1894, p. 110) a dif- 
 ference of elevation of the surface amounting to 
 two miles ought to be readily visible to us on the 
 Earth at certain seasons provided the elevation oi 
 depression involved occurred upon the terminator. 
 It thus appears that we are perhaps on the eve of 
 
102 Mars 
 
 being able to construct a contour map of the planet. 
 The observations involved are however very difficult, 
 and no great accuracy in the results can as yet be 
 expected. 
 
 Strictly speaking the notches in the terminator 
 correspond to variations in the inclination of the 
 surface of the planet rather than to variations in 
 its level, but if we could determine the inclination 
 and knew the distance through which it extended, 
 we should have all the data required for our work. 
 
 There is one conclusion however to which these 
 observations lead us at once. Since these notches 
 in the terminator do not necessarily occur in the 
 darkest parts of the grey regions, and since different 
 portions of them are notched to different depths 
 when on the terminator, it follows that aU portions 
 of the gray regions are not on the same level. In 
 other words hills and valleys occur in them, and 
 consequently the grey regions do not represent the 
 surface of an ocean. 
 
CHAPTER IX 
 
 RECENT STUDIES OF THE MARTIAN AND 
 LUNAR CANALS 1 
 
 It has lately been shown by Messrs. Lane, Maun- 
 der, and Evans that many of the finer Martian 
 canals are probably nonexistent, their appearance 
 being due to certain singular optical illusions. Most 
 of the broader canals, however, in the bright regions 
 of the planet, undoubtedly exist, and the same is 
 almost certainly true of the narrower ones in the 
 light regions, such as Nilosyrtis and Nectar. The 
 chief cause of the illusion seems to be the system of 
 lakes, or oases as they are sometimes called, which 
 were first discovered in large numbers at Arequipa. 
 There is a curious tendency of the human eye to see 
 such dark points united by faint narrow lines, and it 
 has been shown by means of diagrams that these lines 
 sometimes appear when the diagram is at such a 
 distance that the dark dots are themselves invisible. 
 But even without the dots the lines may sometimes 
 appear, joining different portions of the dark 
 
 " Popular Astronomy, 1904, 12, 77. 
 103 
 
104< Mars 
 
 regions. We must therefore divide the Martian 
 canals into two classes, those that are genuine and 
 those that are not. 
 
 Any canal that appears first as a broad streak 
 of measurable breadth, and then gradually narrows 
 as the season progresses may be classed as genuine, 
 although its image may appear by illusion long after 
 the canal itself has really gone. This narrowing of 
 the canals, especially in the bright regions, is very 
 common after the passage of the vernal equinox on 
 Mars. It is also true of several of the canals in 
 the region about Solis Lacus. Any canal on the con- 
 trary which suddenly appears as a faint narrow 
 line joining two dark regions may in the future be 
 looked upon with suspicion, even if to the trained 
 eye it is fairly well seen. To this class perhaps be- 
 long such conspicuous and well-known examples as 
 Phison, Gehon and Euphrates, besides very many 
 other less observed canals. 
 
 This phenomenon of spurious canals is certainly 
 very singular, but we must be careful that its in- 
 terest and unexpectedness do not lead us into the 
 error of affirming that because many Martian canals 
 are spurious, therefore all Martian canals are 
 imaginary. It seems indeed a great pity that so 
 much time and energy should be expended in many 
 observatories in mapping canals in the bright regions 
 of the planet, and comparatively so little time on 
 
ERAT'-iSTHEXES 
 
Studies of the Martian and Limar Canals 105 
 
 the darker regions, where changes are constantly 
 taking place, and where we should naturally expect 
 the most interesting developments to occur. 
 
 Turning now to the other branch of our subject, 
 we find upon the Moon, where the surface conditions 
 are in some respects similar to those upon Mars, 
 although the atmosphere is probably rarer, numer- 
 ous canals, which on account of their proximity are 
 much more readily studied than the Martian ones. 
 While from the Harvard station in Southern Cali- 
 fornia photographs of Mars were secured showing 
 the Syrtis Major, the Fastigium Aryn, and other 
 prominent markings, no one has as yet succeeded in 
 photographing fine enough detail to show a Martian 
 canal. On the Moon, on the other hand, a few canals 
 have already been photographed, both at Arequipa 
 and in Jamaica. Recently a fine photograph has 
 been received through the kindness of Professor 
 Hale, which shows several of the canals to much 
 better advantage than any photograph previously 
 taken. Indeed, it may be said that these latest views 
 taken with the Yerkes telescope show nearly all the 
 detail visible with a 6-inch telescope working under 
 very favorable conditions. 
 
 For purposes of comparison, I have arranged in 
 the plate a drawing of the canals about Eratos- 
 thenes, made in Jamaica, and published in my recent 
 book on the Moon, and an enlargement to the same 
 
106 Mars 
 
 scale of the same region shown in the Yerkes photo- 
 graph. The scale is ^ qqq ooo > ^^ about 32 miles 
 to the inch. The drawing was made August 1, 1901, 
 at 8.6 days after sunrise on Eratosthenes, colongi- 
 tude of the simrise terminator 116°. The photo- 
 graph was taken September 2, 1901, 11.3 days after 
 sunrise, colongitude 149°. While therefore it was 
 taken about three days later in the lunation than 
 the drawing, stUl it does not show any very marked 
 changes to have occurred in the meantime, excepting 
 possibly in the relative intensity of some of the 
 canals. Since the drawing was made only 1.7 days 
 after full moon, when the sun was nearly in the 
 zenith of the crater, and since the same markings are 
 found on other drawings and photographs made at 
 and before full moon, it will be seen that it is geo- 
 metrically impossible that these markings should be 
 due to shadows. They represent therefore real dif- 
 ferences in surface coloration and nothing else. 
 
 The other photograph is an enlargement from 
 the same orfginal negative to the same scale. The 
 region shown is situated four diameters, south 20° 
 west, from Eratosthenes. The dark region at the 
 top is in fact the site of Gruithuison's celebrated 
 mined lunar city. He described a central street from 
 which five or six parallel streets led off on either 
 side at an agle of 45°, Hke the veins of a leaf. 
 Something of the same sort has been seen by several 
 
^iji:t/ir> tfiBBPaffl:^-^ irimc«x.atdLrirg '■l %k4:^ii!a)iSfr 
 
 ^-^^^.aA^=.,j*fe■'^. -jjOilft 
 
 REGIOX XEAIi ERATOSTHENES 
 
Studies of the Marticm and Lvmar Canah 107 
 
 other observers, and I have myself seen a few of 
 the lines. The so-called streets are apparently a 
 difficult and very curious combination of ridges. 
 What interests us most, however, is a series of well- 
 marked canals near the center of the view. Just 
 below the center is a white spot. In this is located 
 a Y-shaped combination of canals. From near the 
 foot of the Y a canal leads off to the right, to a 
 very dark spot. This canal is fourteen miles long, 
 and about half a mile in breadth. A short canal 
 branches off from its upper side, i. e., towards the 
 south, and other canals lead off from the dark spot. 
 Below and to the left of this spot is another one 
 of about the same size. Both are suspected of 
 changing the finer details of their shape in the course 
 of the lunation. 
 
 In my recent researches I have found, and have 
 endeavored to show, that there is a wealth of fine 
 detail upon the Moon, exhibiting constant variations, 
 of the highest interest to the intelligent selenog- 
 rapher. Of these variations, many it is believed are 
 periodic, while some are whoUy irregular in their 
 character. To see them does not involve the use of a 
 large telescope, but it does require a good atmo- 
 sphere, and also a knowledge of the kind of varia- 
 tions one may expect to observe, and of the sort of 
 places in which they are likely to occur. Without 
 this knowledge much time may be wasted in study- 
 ing unfavorable localities. 
 
CHAPTER X 
 
 AN EXPLANATION OF THE MARTIAN ANTD 
 LUNAR CANALS ^ 
 
 When the suggestion of vegetation was first 
 offered to explain the so-called seas and canals of 
 Mars,^ the difficulty was strongly felt that while it 
 readily explained their changes of area, shape, and 
 color, it did not satisfactorily explain the long 
 slender forms of the canals. That these might be 
 due to narrow and therefore invisible water courses 
 was an obvious idea. Professor Lowell in adopting 
 these views added to them the hypothesis of an arti- 
 ficial formation. If the canals were really as straight 
 and uniform as they are generally drawn, it was 
 certainly hard to see how they could owe their origin 
 entirely to natural causes. But now that some of 
 the EngUsh experimenters, Messrs. Lane, Maunder, 
 and Evans have cast doubt on the existence of many 
 of the straight canals, the hypothesis of an artificial 
 origin is materially weakened. 
 
 'Popular Astronomy, 1904, 12, 439. 
 
 ' Science, 1888, 12, S2. Astronomy and Astro-Physics, 1892, 
 H, 670. 
 
 108 
 
An Explanation of the Canals 109 
 
 Another difficulty which early presented itself 
 was to explain what caused the water to flow through 
 the narrow channels, unless we supposed it was ai-ti- 
 ficially pumped through them. This has always 
 seemed to the writer to be the chief difficulty «dtli 
 the whole explanation, but Professor Lowell has 
 now courageously taken the bull by the horns, and 
 adopted the pumping hypothesis.^ If the surface 
 is level, gravity would not come into the question, 
 but we may well ponder upon the amount of energy 
 transformed into work which could furnish enough 
 water to irrigate anywhere from a hundred thou- 
 sand to a few million square miles of surface. 
 
 When the canals on the Moon were discovered, 
 it was thought that they might throw some light 
 upon this puzzling question. It must be remembered 
 that the Moon is about 200 times nearer than Mars 
 at an average opposition, and we can readily imag- 
 ine that if we could increase the power of our tele- 
 scopes 200 times, we might make quite a number of 
 interesting discoveries upon Mars. 
 
 Upon the Moon as upon that planet, several 
 canals frequently radiate from a single lake, but 
 what was most unexpected, the lakes are sometimes 
 found at the bottom of a lunar valley, and sometimes 
 upon the crest of a crater wall. As is the case with 
 Mars also, when the sun rises upon them, and the 
 'Proceedings Amer. Philosophical Society, 1903, 43, 364. 
 
110 Mart 
 
 snow melts, the lakes and canals develop and become 
 conspicuous, subsequently fading out at sunset, 
 which corresponds to the Martian winter. 
 
 It has been shown * that in the lunar crater 
 Alphonsus there are eight variable spots, or lakes 
 as we should now call them. In the exact center of 
 each, excepting the largest one, is found a minute 
 craterlet. In the largest lake there are two large 
 craterlets and five small ones. The canals radiate 
 from the lakes and therefore from these craterlets. 
 The symmetrical arrangement of the lakes about the 
 craterlets in so many instances indicates a causal 
 relation between them, and that the vegetation of 
 the lake, if such it be, owes its origin to some vol- 
 canic action. 
 
 In the case of several of the large craters, notably 
 Tycho, we find a similar radiating structure, and 
 in the case of Tycho even a dark spot or halo at 
 the center. In this case the whole formation is upon 
 so large a scale that its elementary structure can 
 be clearly distinguished. The white radiating lines 
 or bands are seen to be due to numerous minute 
 craterlets, each giving out a triangular white 
 streamer, the alignment of these streamers producing 
 the general effect of a white band. It is probable 
 that this observed regular distribution of the crater- 
 lets is due to their lying along invisible cracks radiat- 
 
 * Harvard Annals, 32, 93. 
 
An Explanation of the Canals 111 
 
 ing from the main crater. It is much the same as 
 the great volcanoes of the Andes, which stretch in 
 a straight line for over 2,000 miles between Peru 
 and the Straits of Magellan. The Alaskan volcanoes 
 lie upon a uniformly curved line of nearly equal 
 length. Most of the terrestrial volcanoes are dis- 
 tributed along similar lines. This line formation is 
 generally considered by geologists to be due to sub- 
 terranean lines of weakness or cracks in the earth's 
 crust. Such being the case, it seems probable that 
 the canals on the Moon lie along similar invisible 
 cracks radiating from the small craterlet at the 
 center of each lake. These cracks are not always 
 straight but such is their general tendency. Under 
 favorable Ulumination small cracks are found to be 
 very common upon the surface of the Moon, and in 
 the cases of Petavious, Alphonsus, and Atlas that 
 class of cracks that we have designated from their 
 shape as river-beds are seen to be intimately asso- 
 ciated with the lakes and canals.^ It is believed 
 that enough water vapor and carbonic acid escape 
 from the central craterlet and flow down its sides 
 to develop the vegetation upon its slopes, and that 
 the smaller quantities escaping from various points 
 along the radiating cracks similarly develop the 
 vegetation which shows along their sides. In addi- 
 tion to the escaping vapor, water itself might issue 
 ' Harvard Annals, 32, 98 and 112, see also Plate VII. 
 
112 Mars 
 
 from the subterrjanean crack and percolating 
 through the soil be evaporated from its surface. 
 
 It is not thought that there is any transfer of 
 vapor lengthwise of the crack but that on account 
 of the lack of external atmospheric pressure the 
 vapor rises quietly directly from the lower regions, 
 owing to the internal heat of the Moon. As soon as 
 the exterior is sufficiently warmed by the sun, the 
 vapor and gas would begin to appear. On account 
 of the rarity of the atmosphere, instead of rising 
 they would immediately spread themselves along the 
 surface of the ground. Even in desert regions upon 
 the Earth we should therefore scarcely expect to 
 find similar formations unless actually irrigated by 
 water, instead of water vapor. In its physical con- 
 dition Mars seems to occupy an intermediate posi- 
 tion between the Earth and the Moon. 
 
 It seems to the writer that the merit of this ex- 
 planation lies not so much in its novelty, but rather 
 because it is founded so largely upon observed facts. 
 
CHAPTER XI 
 
 THE DOUBLE CANALS OF MARS ^ 
 
 A few years ago the doubling of the Martian canal 
 system was generally admitted by astronomers as an 
 accepted fact. Latterly however doubts have begun 
 to arise with regard to it. It was shown by the 
 writer, in the Harvard Annals XXXII, 149, that 
 accepting the results of Schiaparelli, Flammarion, 
 Antoniadi and Lowell, the double canals had this 
 curious property, namely, that their linear separa- 
 tion was inversely proportional to the diameter of 
 the object-glass of the telescope, and directly pro- 
 portional to the distance of the planet. 
 
 It was then suggested that some one who was 
 able to see the duplication of the canals, which the 
 writer has never been able to do, should make meas- 
 ures of their separation, using different apertures 
 in front of the telescope upon the same night. This 
 has now been done by Professor Lowell, Bulletin 5, 
 Lowell Observatory, and a recent examination of 
 his work, has shown that he has brought out some 
 very instructive results. 
 
 ' Popular Astronomy, 1904, 13, 385. 
 113 
 
114 Mars 
 
 In the first place as far as he is concerned it is 
 evident that the separation of the canals is inde- 
 pendent of the aperture of the telescope employed. 
 Secondly, he has found that the duplication of the 
 canals can be seen with surprisingly small apertures. 
 Thus with six inches he divides the three double 
 canals Euphrates, Hiddekel, and Gihon when their 
 components were separated only 0".27, 0".26, and 
 0".28 respectively. 
 
 It was found by Dawes that an objective one 
 inch in diameter could separate (not merely elon- 
 gate) two equal stars 4<".56 apart. A ,6-inch objec- 
 tive should therefore separate stars at one-sixth 
 this distance, or 0".76. Experiments made at Cam- 
 bridge with a 15-inch aperture ' Harvard Annals 
 XXXII, 149, showed that in order to divide two 
 lines drawn in ink on white paper, they must be 
 separated by an angle of 0".42. For a 6-inch objec- 
 tive the required separation would therefore be 
 1".05. 
 
 An analogous experiment may be readily repeated 
 without instruments. Draw two lines in ink 1 milli- 
 meter, or one twenty-fifth of an inch apart, on white 
 paper. Placed at a distance of ten feet they can 
 just be divided with the naked eye. Their separation 
 will be 70". The diameter of the pupil of the eye 
 in a brightly lighted room is about one-tenth of an 
 inch. If we can conceive the pupil enlarged sixty 
 
T?ie Double Canah of Mars 116 
 
 times, which is what is practically done by a 6-inch 
 telescope, we should be able to separate the lines at 
 one-sixtieth of this distance apart, or at 1".15. 
 
 Summarizing our results, and applying them to 
 the case of a 6-inch telescope, we find from Dasve-i' 
 experiments, confirmed universally by astronomers, 
 that two stars could only be separated when as 
 much as 0".76 apart. The less the contrast the 
 more difficult the separation. Therefore for black 
 lines on white paper we need a greater separation 
 than in the case of the stars. Our telescopic experi- 
 ments with black lines indicate that the angle must 
 measure 1".05. Our naked eye experiments make 
 the angle 1".15. In the case of Mars, Professor 
 Lowell can detect the duplication when the separa- 
 tion is only 0".26. This would be equivalent in the 
 case of the naked eye experiment to separating two 
 lines one millimeter apart at a distance of forty 
 feet. This the reader will find is quite impossible. 
 
 The writer hesitates to believe that Professor 
 Lowell can separate two actual lines which are do 
 much nearer together than the limit for other ob- 
 servers, and thinks therefore that what he sees 
 must be some optical illusion. 
 
CHAPTER XII 
 THE EXPECTED MARTIAN SNOWS ^ 
 
 It may interest observers to know that ice will 
 probably begin to form at both poles of Mars during 
 the month of April. The north pole will be turned 
 toward the Earth at an angle of from 10° to 13° 
 during the month, and the meteorological changes 
 that we may expect - to see when the ice appears 
 should be quite conspicuous, the northern ice melting 
 rapidly in the continuous sunshine. The poles may 
 appear either a pure white, a light yellow or a bright 
 but vivid green. The first indicates hoar frost or 
 snow, the second clouds, and the third, at least in 
 part, vegetation. The green over a considerable 
 portion of the planet will be particularly vivid dur- 
 ing the present opposition, and should be visible 
 even in small telescopes. A paper on Martian Mete- 
 orology is now in preparation for the Harvard An- 
 nals treating this subject in more detail, but it prob- 
 ably will not be ready for distribution before sum- 
 mer. 
 
 'Popular Astronomy, 1905, 13, 196. 
 116 
 
The Martian Snows IIT 
 
 The planet will be from 13" to 17" in diameter, 
 coming to opposition early in May, so that the disc 
 will be large enough to be well seen. Indeed, this 
 opposition will be particularly favorable to these 
 observations, the planet being nearer us and better 
 placed during this portion of its year, than during 
 either the preceding or following oppositions. It is 
 unfortunately rather far to the south, declination 
 — 18°, and observations at the beginning of the 
 month cannot be made much before midnight, — - 
 meridian passage 14h. 53m. By the end of the month 
 observations may begin shortly before ten o'clock, 
 — meridian passage 12h. 39m. 
 
 OBSEEVED 
 
 In the April number of Popular Astronomy atten- 
 tion was called to this planet, and the opinion ex- 
 pressed that the polar caps should appear during 
 the month. Owing to the press of other matters it 
 was not possible to maintain visual observations in 
 Cambridge, but photographs were obtained under 
 the direction of Mr. King with the 11-inch Draper 
 telescope whenever practicable. An enlarging lens 
 was employed, giving the original negative on a scale 
 of about 2. "5 to the millimeter. 
 
 The first photograph was taken upon March 31, 
 
118 Mars 
 
 others being secured upon April 1, 2, 8, 15, 16, 18, 
 23, 25, 27, and 30. The first photograph showed 
 clouds at both the limb and terminator, but no polar 
 caps properly so-caUed appeared until April 23, 
 when a large Ught area was clearly visible at the 
 south pole. It did not appear bright enough for 
 snow, however, but more resembled an extensive 
 cloudy region. It has remained visible upon the 
 photographs since that date, although with slightly 
 diminished intensity and size. A minute bright area 
 appeared near the north pole on April 15, but was 
 seen only with difficulty. 
 
 A visual examination of Mars was made on the 
 night of April 30, with the 24-inch reflector. The 
 southern polar cap was clearly visible, extending 
 far to the north in longitude 340°, but its inten- 
 sity was slight, little exceeding that of the limb in 
 other regions. It is probable that when the Mar- 
 tian clouds clear away, snow will be found lying in 
 their place. 
 
 The heliocentric colongitudes of the planet upon 
 April 15 and 23 were 216° and 220°. These posi- 
 tions would correspond on the Earth to August 3 
 and 7, or to near the end of the winter of the south- 
 ern hemisphere. Snow seldom comes earlier upon 
 Mars. Extensive green areas should be visible in 
 June, and the Mare Erythraeum recently described 
 
The Martian Snows 119 
 
 by Professor Lowell as brown, should by that time 
 have recovered its normal color. This change of 
 color with the seasons seems to the writer the best 
 proof of the existence of vegetation on Mars. 
 
CHAPTER XIII 
 WHAT WE KNOW ABOUT MARS ^ 
 
 During the next three years the planet Mars will 
 twice approach nearer to the Earth than has been 
 the case since 1892. It will, therefore, be a very 
 conspicuous object in the heavens, equaling Jupiter 
 in brilliancy, and will excite considerable attention 
 from astronomers in various parts of the world. 
 
 THE ORBIT OF MAES 
 
 To understand why, unlike the case of the other 
 planets, these near approaches occur only at such 
 long and irregular intervals, let us imagine the larger 
 circle (Fig. 1) to represent the orbit of Mars, and 
 the smaller one the orbit of the Earth, the Sun being 
 at S. These orbits are not really circles, but ellipses, 
 the Sun being a little to one side of the exact cen- 
 ter in each case. The intersections of the two in- 
 clined diameters P A, pa, with the orbits, show where 
 ' The Technical World Magazine, 1906, 460. 
 120 
 
What We Know About Mars 
 
 m 
 
 the planets are nearest and farthest from the Sun. 
 When Mars is nearest the Sun it will be seen that 
 the Earth is nearly at its greatest distance, which 
 brings the two orbits closer together there than 
 elsewhere. 
 
 The Earth moves in its orbit much faster than 
 Mars, and also has a shorter distance to travel ; it 
 therefore overtakes Mars once in a little over two 
 years. When this is the case, the two planets are 
 much nearer together than at other times. Mars 
 then rises just at sunset ; and since it is in the op- 
 
 170" 
 
 Fig. 1. Debits of the Eaeth and Mabs 
 
U2 Mars 
 
 posite part of the sky to the Sun, it is said to be 
 in opposition. In the figure, the short lines con- 
 necting the two orbits show where the different op- 
 positions have occurred. In that of 1892, the two 
 planets were very near together; in 1894 they were 
 somewhat farther apart; but no favorable opposi- 
 tion has occurred since then. The next one will take 
 place in 1907, and will be a little better than that 
 of 1894. The distance of Mars from the Earth will 
 then be 38,200,000 miles, while the shortest possible 
 distance is 35,000,000 miles. The most favorable 
 oppositions occur in the latter part of August. 
 
 The parts of the Martian orbit marked n and s 
 in the figure, show when the planet's poles are pointed 
 most nearly towards the Sun. Thus at s is the south- 
 ern summer and northern winter. Since the planet 
 is here so much nearer the Earth than at n, it is pos- 
 sible for us to see the details of its southern hemi- 
 sphere very much better than we ever can those of 
 its northern one. 
 
 The inclination of the equator of Mars to its or- 
 bit is 24°, or about the same as that of the Earth. 
 The seasons on the two planets are therefore iden- 
 tical, except that, on account of the longer year, 
 those on Mars are twice as long as our own. The 
 Martian day is about forty minutes longer than 
 ours. 
 
What We Know About Mars 123 
 
 GEAVITATION, WATER, AND ATMOSPHEEE 
 
 The diameter of Mars is 4,200 miles, or a little 
 over half that of the Earth. Its mass, or the amount 
 of matter it contains, is 0.12 as compared with that 
 of the Earth; and the force of gravity at its sur- 
 face, 0.38, or about two-fifths that at the surface 
 of the Earth. A man weighing 150 pounds on the 
 Earth would weigh rather less than 60 pounds on 
 Mars, and could accordingly be much more active. 
 He could jump much higher and throw a stone two 
 and a-haK times as far. It will be noticed that he 
 could not move the stone any faster than he could 
 upon the Earth ; merely, it would take longer to 
 fall, and therefore would go farther before striking 
 the ground. 
 
 The effect of this small constant of gravitation 
 has a most important influence on the physical con- 
 ditions at the surface of Mars. Bodies where this 
 constant is large, like the Sun and stars, can re- 
 tain enormous atmospheres of the lighter gases, like 
 hydrogen and heliiun, which escape at once into outer 
 space from the Earth's atmosphere. Bodies where 
 the constant is small, like our Moon, lose nearly 
 all their atmosphere, save such components as are 
 being constantly liberated from their interior, like 
 
124 Mars 
 
 water vapor and carbonic acid. Mars, where the 
 constant of gravitation lies between those of the 
 Earth and Moon, must have an atmosphere inter- 
 mediate in its density and composition. That its 
 atmosphere contains water vapor, we know, because 
 we see it frozen at its poles in the form of ice, and 
 later melted to form water. It is sometimes sug- 
 gested that this white material, which increases in 
 winter and diminishes in summer, may be carbonic 
 acid; but this cannot be the case, since carbonic 
 acid does not become liquid at pressures of less than 
 five atmospheres, no matter what the temperature 
 may be. The atmosphere of Mars, we know, is very 
 rare ; therefore the liquid we see surrounding the 
 melting ice-caps cannot be carbonic acid. There is 
 no substance known, save water, that would meet 
 these conditions ; therefore, if the polar caps of Mars 
 are not due to ice, they must be caused by some 
 substance that is not found upon the earth — which 
 conclusion is improbable. 
 
 Water is nevertheless very scare on Mars ; and its 
 oceans, if it has any, are shallow and only tempo- 
 rary, existing solely at the times of the spring 
 freshets. In Fig. 2 is shown the south polar cap 
 after the ice has begun to melt. Below, and to the 
 right of it, is seen a very dark area, which the polari- 
 scope shows differs from the rest of the planet in 
 
FIC. i. SOUTH POLE OF MARS 
 
 Showing White Pohir Cap. From ; 
 
 drawing hy tlie writer 
 
 FIG. o. REGIOX .VISOUT 
 
 SYHTIS MIXOK, SHOWI.VG 
 
 S( >.ME Sin IHT ,\NU EXTREMELY 
 
 XARROW C-iNAL-S 
 
 .\ lake ne ir center of one of the 
 
 sea^ is al.so shouii, jnst alajve 
 
 center of the tii^nre. From a 
 
 lirawiiit; liy tile writer in l«!l-t 
 
 FIG. 4. I'HtlTOGRAPH OF 5L\H,S TAKEX AT II.VR\ARD OB- 
 SERVATORY .\XI) THE IHRVARI) STATIO.V OX MOUXT WTLSOX 
 IX SOITMERX ( ALIFORXIA IX 1 HSS AXD l.SiMI 
 
What We Know About Mars 125 
 
 that it has a shiny surface.^ In the springtime, 
 shortly after the ice has begun to melt, this dark 
 area forms a ring surrounding the ice, measuring 
 some two thousand miles in diameter and in some 
 places over two hundred miles in breadth. As the 
 ice-cap diminishes in size, the black border retreats 
 with it towards the pole. This leads us to believe 
 that the black area is due to a swamp or a collection 
 of swampy pools and streams, rather than a sea. 
 Within the ice-cap is seen a lake connected with the 
 swamp by a narrow strait. 
 
 If the ice-cap, when at its maximum size, contains 
 the larger part of the total water supply of the 
 planet, it will not be difficult to form an idea of its 
 volume. Let us assume that the mean depth melted 
 by our Sun in four of our months over the whole 
 area is twenty feet, and that the ice has the con- 
 sistency of snow. This, when melted, would give us 
 a lake 2,000 miles in diameter and two feet in depth. 
 This would be about the amount of water con- 
 tained in one of our great lakes. One thousand 
 times this amount would be insignificant compared 
 to our terrestrial oceans. 
 
 Probably water would not now be found on the 
 planet at all, if, as in the case of our Moon, it were 
 not constantly renewed from the interior. Fresh 
 
 " Astronomy and Astro-Physics, 1894, 13, 554. 
 
126 Mart 
 
 supplies are thus gradually taking the place of that 
 which is being slowly dissipated into space. Sooner 
 or later these supplies must be exhausted ; and then, 
 if not before, aU life on both these bodies must cease. 
 On our Earth too, when our volcanoes cease to evolve 
 carbonic acid, plant life, and with it all animal life, 
 must necessarily come to an end. 
 
 Oxygen and nitrogen may exist upon Mars, but 
 probably in small quantities. Campbell has shown 
 by spectroscopic evidence, that the density of the 
 Martian atmosphere cannot exceed one-quarter that 
 of our own, and is probably much less. The exist- 
 ence of water in the liquid form shows that the den- 
 sity of the Martian atmosphere must exceed 1-150 
 that of the Earth. As far as we know at present, 
 therefore, the equivalent pressure of the Martian at- 
 mosphere is less than 7.5 inches, and is more than 
 0.2 inch. The light and absorption visible at the 
 bright edge of Mars indicate that the true value 
 lies nearer to the upper of these limits than it does 
 to the lower one. The lowest pressure at which 
 man can live, as shown by recent experiments made 
 by inhaling oxygen and carbonic acid combined, is 
 about 5 inches ; and that is probably only for a 
 short time; but doubtless an intelligent race might 
 be slowly evolved, capable of sustaining life at still 
 lower pressures. 
 
What We Know About Mars 127 
 
 CLIMATE AND METEOEOLOGY 
 
 The fundamental fact on which we must base our 
 knowledge of the climate of Mars, is the melting of 
 its polar snows. Where these are melting, the tem- 
 perature must be 32° F. ; and nearer the equator 
 it must be warmer. The climate of the Earth is 
 tempered by our great oceans. Otherwise our sum- 
 mers would be much hotter, and our winters much 
 colder. In the heart of the continents, the extremes 
 are much greater than on the coast. On Mars, 
 where there are no permanent oceans, the extremes 
 must be greater still. Our atmosphere also serves 
 to moderate our climate. On high mountain sum- 
 mits, the extremes are much greater than at sea- 
 level. The comparatively rare atmosphere of Mars 
 must be of little use in this respect. 
 
 Certain causes tend to raise the mean temperature 
 of Mars. The relatively large amount of cloud and 
 illuminated snow areas of the Earth, cause a great 
 waste of heat by reflection, which does not occur 
 upon Mars. If the nights of Mars are compara- 
 tively cloudy, as may be the case, these clouds would 
 help to protect the planet from radiation into space 
 during that portion of the Martian day, and thus 
 also tend to raise its temperature. 
 
128 Man 
 
 In the summer season, on account of the rare 
 atmosphere and the lack of water, the arctic re- 
 gions on Mars must enjoy a temperature but little 
 lower than that of the torrid zone, but during the 
 long winter night the polar cold must be intense, 
 and but little removed from absolute zero — that is 
 — 460° F. As to the highest temperature experi- 
 enced on Mars, we have no information, but may 
 suppose it to be inferior to that found upon the 
 Earth. In the torrid zone, humanity would possibly 
 find the range of temperature disagreeable, but prob- 
 ably not unbearable. Even in the polar regions, 
 vegetation, if not animal life, might exist, much as it 
 does with us. 
 
 The clouds of Mars for some unknown reason ap- 
 pear yellowish in color. On the surface of the disc, 
 although visible, they are not conspicuous, but can 
 readily be photographed. On the terminator they 
 are at certain seasons easily seen. In the opposition 
 of 1894, many were recorded at Flagstaff. The pro- 
 jection on the left-hand side of Fig. 3 is due to cloud. 
 Only three clouds are on record which could be iden- 
 tified upon two successive nights. These all were 
 discovered at Flagstaff, and were seen in the years 
 1894,3 1900,* and 1903.^ They appeared in what 
 
 'Astro-Physical Journal, 1895,1, 127; also "Mars," P. Lowell, 
 70. 
 
 ■* Proceedings, American Philosophical Society, No. 167, page 
 166. 
 
 'Lowell Observatory Bulletin No. 1. 
 
What We Know About Mars 129 
 
 would correspond to the late summer or autumn upon 
 the planet, two within and one near the borders of 
 the torrid zone, all within 60° of the Sinus Sabaeus. 
 They were all three at an altitude of about fifteen 
 miles, and moved in a general northwesterly direc- 
 tion, with velocities of from 13 to 27 miles per hour. 
 These altitudes are much greater than those of ter- 
 restrial clouds, while the velocities indicate a com- 
 paratively sluggish atmospheric circulation, which 
 is what we should expect. 
 
 The nine photographs shown in Fig. 4 are the first 
 ones ever taken showing detail upon Mars. Draw- 
 ings and photographs of the planets are always 
 turned so that south shall be at the top. The right- 
 hand side is called east. The bright edge is called 
 the "limb"; the dark edge, which is where the Sun is 
 rising or setting, is called the "terminator." 
 
 The first photograph shows the equatorial cloud- 
 band. The second shows the north polar cap. The 
 third was taken the next day, and shows the forma- 
 tion during the twenty-four hours of a new south 
 polar cap. The fourth was taken five days later, 
 and shows the increase in size of this cap. The fifth 
 photograph shows the cap well developed, also a 
 faint equatorial cloud-belt, and below it one of those 
 mysterious white spots which are never found far 
 from the equator. Unlike the clouds, these spots do 
 not change their position, but persist for long pe- 
 
130 Mart 
 
 riods of time. This one was still visible, although 
 faint, at the end of six weeks. There are no moun- 
 tains on Mars to collect clouds, save possibly a short 
 range near the south pole. It does not seem likely 
 that this spot was due either to ice or to clouds. It 
 was located near the Trivium Charontis, in longi- 
 tude 205°, latitude + 15°. A similar though less 
 conspicuous white spot had been observed on the 
 equator in longitude 300°, in 1892, at Arequipa, and 
 in 1901 and 1903 at Flagstaff. The spot near the 
 Trivium is visible only during the summer season on 
 Mars, its first recorded equivalent date of visibility 
 being June 2, and the last September 13. It is pos- 
 sibly due to vegetation. If so, it is perhaps appro- 
 priate that SchiapareUi should have designated this 
 region under the name "Elysium." 
 
 The ninth photograph shows the decreasing size 
 of the southern ice-cap, while a temporary belt of 
 cloud surrounding the north pole is also shown. A 
 study of photographs like these enables us to deter- 
 mine the duration of the cloudy and clear spells upon 
 Mars. Continuous cloudy weather near the equator 
 or tropics is very rare, but in the polar regions the 
 clouds frequently last for weeks at a time. The in- 
 tervening periods of clear weather are also of 
 long duration.* The three remaining photographs 
 show permanent details upon the disc. The dark 
 
 "Annals, Harvard College Observatory, 63, 168. 
 
What We Know About Mars 131 
 
 spot just above the middle of the sixth view is the 
 Sinus SabsEus, from which Martian longitudes are 
 reckoned. The dark spot on the two others is the 
 Syrtis Major. 
 
 SEAS, CANALS, AND LAKES 
 
 The first drawing ever made of a dark area or sea 
 on Mars was of this same Syrtis Major, by Huygens, 
 in 1659. The first map showing a canal and lake 
 was constructed by Beer and Maedler in 1840. The 
 canal was Daemon ; the lake, Lacus Phcenicis. The 
 canals were first recorded in large numbers by Schia- 
 parelli in 1877 ; the lakes, at the Harvard station in 
 Arequipa in 1892, when forty of them were observed. 
 
 A large telescope is not necessary in order to see 
 clearly the canals and lakes. One of eight or ten 
 inches aperture is ample. The really important 
 requisite, however, is a steady atmosphere, such as 
 is found only in low latitudes, which gives what as- 
 tronomers technically call "good seeing." This ex- 
 plains why it is that Mars cannot be studied to ad- 
 vantage at the large northern observatories, where, 
 with the most superb optical equipment, little or 
 nothing save the coarser detail can be seen upon its 
 surface. 
 
 Doubt has recently been expressed, in some of the 
 
132 Mart 
 
 foreign periodicals, even as to the existence of the 
 canals. An astronomer who has never looked through 
 a telescope, except in northern Europe or the eastern 
 United States, has no right to express any opinion 
 on the subject, because he simply does not know what 
 good seeing looks like, and his opinion is therefore 
 valueless. He might as well express his views on 
 electro-dj'namics or physiology. The comparatively 
 small number of astronomers who are familiar with 
 good seeing, and have looked at Mars, have seen the 
 canals, and consequently do not doubt their exist- 
 ence. 
 
 Our present telescopes are plenty large enough 
 for purposes of planetary research ; indeed, some of 
 them are too large, and no gain can be secured by 
 trying to improve them. In Cambridge an aperture 
 of 6 inches wiU show everything on the Moon or 
 Mars that can be seen with a 15-inch telescope. At 
 Flagstaff, where the seeing is much better, Professor 
 Lowell has stated that he often reduces his aperture 
 from 24 to 16 inches in order to see more distinctly. 
 T\Tiat we must now do is to try to find places on the 
 Earth where the seeing is better than anything yet 
 discovered, and erect our future telescopes there. 
 Then we can perhaps use still larger apertures to 
 advantage. Heat or moisture have nothing what- 
 ever to do with the seeing; it is chiefly a question of 
 latitude; and in low latitudes, such as Arequipa 
 
What We Know About Mars 133 
 
 — 16°, and FlagstafF + 36°, the seeing is often 
 very good indeed. The reason of this is that these 
 places are far removed from the great cyclonic dis- 
 turbances which affect our atmosphere in the tem- 
 perate zones. At these places, the canals of Mars 
 are perfectly distinct. To understand how the 
 planet appears there through a large telescope, we 
 may examine the Moon some night through a small 
 opera glass. The sharpness and amount of detail 
 visible in the two cases will be similar, although the 
 appearance of the two bodies is quite unlike. 
 
 In former times the red color of the planet was 
 supposed to be due to its atmosphere. Later it was 
 seen that this was impossible. The dark spots on 
 its surface were next thought to be water, and were 
 called seas ; while the bright red areas were supposed 
 to be due to vegetation, which it was imagined must 
 be of that color upon Mars. Later the writer sug- 
 gested that the so-called seas and canals were the 
 real vegetation, the red areas being desert regions.^ 
 This view was strongly confirmed by the Arequipa 
 observations of 1892, and the Flagstaff observations 
 of 1894, and has since been generally adopted, al- 
 though the old names, for the sake of their con- 
 venience, are still retained. 
 
 One out of several difficulties in supposing that the 
 
 ' Science, 1888, 12, 83. Astronomy and Astro-Physics, 1893, 
 11, 670. 
 
134 Mars 
 
 seas and canals are due to water, is that many of 
 the canals cross the seas, which it is difiBcult to ex- 
 plain on that hypothesis (see Figs 5 and 11). Some 
 of the lakes on the planet, also, are located in the 
 seas. The latter are found to be a vivid green in 
 what corresponds to the springtime of Mars. After- 
 wards they turn grey ; and still later those of them 
 near the poles become yellow. They are then distin- 
 guished only with difficulty from the soil of the desert 
 regions of the planet. In a recent observation made 
 at this season by Lowell at Flagstaff, the Mare 
 Erythrasum was found to have turned a chocolate 
 brown, a color which on the Earth we should asso- 
 ciate with fertility. The writer has seen the same 
 color exhibited at the time of the drying up of the 
 temporary south polar ocean. The canals are usu- 
 ally too narrow to have any appreciable color, al- 
 though in the case of the broader ones their color 
 is thought sometimes to resemble that of the seas. 
 Sometimes it is described by both Schiaparelli and 
 Lowell as brown. 
 
 Their breadth is very uncertain; some observers 
 like Douglass draw them very wide (see Fig. 5) ; 
 others like Lowell, from whose drawing Fig. 6 is 
 copied, extremely narrow. The writer gives them an 
 intermediate breadth (see Fig. 10). Occasionally, 
 with conditions favorable to the best seeing, short 
 and extremely narrow canals have been seen by the 
 
REGION ABOUT 
 MAJOR 
 Draivn l..v A. E. \>„ng\„i 
 
What We Know About Mars 135 
 
 writer (Fig. 3) ; but the long canals never appear 
 to him as narrow as they are drawn by Lowell. 
 
 Fig. 6. Region about Sybtis Fig. 7. Markings on the 
 
 Major Surface of Mars 
 
 From a drawing by Professor Drawn by writer from two 
 
 Lowell. photographs taken at Flag- 
 
 staff. 
 
 Recently Mr. Lampland at Flagstaif has suc- 
 ceeded in photographing some of the canals. At first 
 it was supposed that these photographs would serve 
 to convince the doubters of their existence ; but it 
 was soon found that those who doubted the canals 
 were also unable to see them on the photographs, so 
 that the photographic argument seemed to have a 
 minus value. Photographically the canals are ex- 
 tremely difficult objects, and it does not surprise the 
 writer that those unused to astronomical photo- 
 graphs, could not make them out. 
 
 A drawing from the photographs was made by Mr. 
 Wesley and published in The Observatory the past 
 year. Fig. 7 is a drawing by the writer, based 
 
136 
 
 Mars 
 
 chiefly on the third, but partly on the first photo- 
 graph issued in Bulletin No. 21 of the Lowell Ob- 
 servatory. The other photographs were also con- 
 sulted, and no marking was considered assured which 
 did not appear upon at least one of the others. 
 These photographs were taken about an hour after 
 the drawing by Professor Lowell (Fig. 6) was made. 
 A comparison of the two shows very clearly a tend- 
 ency on his part to draw the detail too small, in 
 comparison with the diameter of the disc. 
 
 Fig. 8. Ki:t Map Gifing Names of Canals and Other 
 Feattjees 
 
 Fig. 8 will serve as a key to the names of the 
 canals discussed, which Lowell states are visible on 
 the photograph. The main features — Hellas, Mare 
 ErythrsBum, Mare Icarium, and Syrtis Major — are 
 all obvious on the originals from which Fig. 7 was 
 sketched. The canals Nilosyrtis, Casius, and Pyra- 
 mus are also perfectly clear, but, it will be noticed, 
 do not appear on the photograph as canals at all, 
 
What We Enow About Mars 137 
 
 but as broad areas. Regarding the last two, this 
 is true also of Lowell's drawing. His drawing of 
 the first is certainly too narrow, as proved by the 
 photographs. Of the remaining canals described by 
 him — which come down as narrow lines in the photo- 
 graph — Thoth, Astaborus, and Protonilus are fairly 
 clear. Vexillum, Pierius, and Ismenius Lacus are 
 more difficult, but apparently shown. 
 
 As a photographic triumph, these results are well 
 worthy of record ; and when we consider how difficult 
 it is to photograph fine detail that is not merely 
 obvious but even conspicuous to the eye, the photo- 
 graphs bear strong testimony to the distinctness with 
 which the canals must have been visible at Flagstaff 
 on the day in question. 
 
 Intermediate between the doubters and Professor 
 Lowell's immediate following, there is a large class 
 of persons who deny some of the fainter canals, and 
 who doubt the uniformity of structure of the others. 
 They say his canals are too regular, too narrow, and 
 too straight — that if they were better seen they 
 would be found to be made up of short broken lines 
 of varying width, and perhaps, in places, of irregu- 
 lar spots. This proves to be the case with the lunar 
 canals. With poor seeing and a low magnification, 
 they seem to be perfectly smooth and straight, like 
 the Martian ones ; but with good seeing and a higher 
 power, they are found to be quite irregular. Why 
 
138 Mars 
 
 should it not be true also on Mars? To this, Mr. 
 Lowell replies that the lunar canals consist of dark 
 markings lying along natural cracks, while the Mar- 
 tian canals are artificial. This may be so, but it 
 would be hard to prove it. 
 
 Again, amidst numerous irregular and nearly in- 
 visible markings, the human eye, when straining for 
 the faintest possible detail, naturally connects con- 
 spicuous objects by straight lines. Is it not possible 
 therefore that many of these fainter canals are 
 merely subjective effects? 
 
 The point of all this criticism is that the numer- 
 ous long, straight lines give the planet a very arti- 
 ficial appearance. If the lines were more broken and 
 irregular, they would look more like natural mark- 
 ings, more in fact like what we find upon the Moon. 
 In short, the argument in favor of intelligent inhabi- 
 tants would be greatly weakened. 
 
 DUPLICATION or THE CANALS 
 
 In 1882, Schiaparelli announced that the canals 
 in Mars were sometimes double. One day a canal 
 would be clearly seen, on the next day, or even a few 
 hours later, there would be two in its place. Later 
 the two would disappear, and again the canal would 
 be single. Sometimes the single canal would coin- 
 cide with one of the pair, but more frequently it 
 
What We Know About Mars 1S9 
 
 would coincide with neither of them. When we con- 
 sider that these double canals were often as much as 
 200 miles apart, these sudden changes seemed in- 
 credible. 
 
 Fig. 9. Duplicate Canals, fhom Drawing by Peofessob 
 
 Lowell 
 Opposition of 1903. Sinus Sabaecus is near top of disc; Syrtis 
 Major on the left. 
 
 When Lowell confirmed the duplication of the ca- 
 nals (see Fig. 9), many astronomers hesitated to ac- 
 cept it. In fact his observations even seemed to make 
 it still more improbable. He measured their separa- 
 tion with telescopes of different apertures, and suc- 
 ceeded in seeing the duplication when both by theory 
 and observation it should have been invisible. More- 
 over, with a few exceptions, the only drawings he 
 published showing the double canals were made by 
 himself ; and these exceptions were mostly made by 
 Douglass, who, in the published text, expressed grave 
 doubts as to the objective reality of the duplica- 
 
140 Mars 
 
 tion. It is true, several other observers using much 
 smaller telescopes claimed to see it; but it always 
 happened to be just at the limit of visibility of their 
 telescopes, no matter what the size of their instru- 
 ments chanced to be. One of the most skilful of these 
 observers, M. Antoniadi, later published his doubts 
 as to the genuineness of what he had seen. On the 
 other hand, most of the observers who used large 
 telescopes always saw the canals single. Naturally 
 the astronomers were not convinced. 
 
 Now further observations have been made, and 
 new facts brought to light that partially explain this 
 singular phenomenon. According to Professor 
 Lowell only about one-quarter of aU the canals are 
 ever seen to be double, and they are probably double 
 aU. the time.^ It is only when they are very faint 
 that they appear single, and their faintness is ap- 
 parently the reason that the duplication does not 
 then show. This is due to the fact that under these 
 circumstances one canal is somewhat fainter than 
 the other, and so escapes detection. According to 
 his views, the single canal always coincides in posi- 
 tion with one of the two components of the double. 
 
 The double canals usually appear, he says, as a 
 
 broad, hazy band; it is only by glimpses that the 
 
 duplication is seen. There is nothing improbable 
 
 in the idea that one-quarter of the canals should be 
 
 'Lowell Observatory Bulletin No. 15. 
 
What We Enow About Mars 141 
 
 permanently broad and the rest permanently nar- 
 row. The only question is, Is it likely that either 
 the middle of these canals should fade out, leaving 
 the sides dark, or that the sides should darken, leav- 
 ing the middle bright? 
 
 It is a fact that some of the seas, as the season 
 progresses, will fade out across the middle in places, 
 leaving the rest dark, and thus present on a com- 
 paratively large scale a phenomenon similar to that 
 claimed for the double canals. This same effect oc- 
 curs upon the floor of the lunar crater Eratosthenes, 
 forming two widely diverging canals. A long, double 
 canal is also found upon the rim of this crater, but 
 this is clearly due to the presence of two long, paral- 
 lel cracks. A similar chance occurrence might oc- 
 casionally be found upon Mars, but it seems to the 
 writer in the light of the facts, and especially of the 
 opinions of Messrs. Douglass and Antoniadi, that 
 the case for a systematic duplication will not be 
 proved until more well-known observers, favorably 
 situated and circumstanced, have recorded it. 
 
 SEASONAL CHANGES 
 
 Perhaps Lowell's most interesting recent investi- 
 gation is on what he calls the Cartouches of the 
 Canals — that is, their variable visibility dependent 
 
142 Mar$ 
 
 on the Martian seasons.' He finds that soon after 
 the begnining of the melting of the northern ice-cap, 
 the canals begin to develop in the north polar re- 
 gions. These are immediately followed by the ca- 
 nals in the north temperate zone. A few weeks later, 
 those in the torrid zone develop ; and still later, 
 those in the south temperate. The process of de- 
 velopment, therefore, is carried on across the equa- 
 tor. This is most naturally explained by the growth 
 of vegetation following the annual transference of 
 water from pole to pole. The speed of transfer he 
 finds is at the rate of two miles per hour. 
 
 The striking difference between Mars and our 
 planet is that in our equatorial regions, where we 
 have plenty of water, there is continued fertility 
 throughout the year. On Mars the vegetation must 
 wait until the water reaches it semi-annually from 
 the poles. There are accordingly two fertile and 
 two barren seasons. 
 
 Professor Lowell concludes that the water is trans- 
 ferred artificially from pole to pole. In this we can 
 hardly foUow him, since with the rare atmosphere, 
 and accordingly rapid evaporation and condensa- 
 tion upon Mars, the aqueous vapor would necessarily 
 flow across the planet's surface of itseK, being al- 
 ternately condensed at each pole by the winter's 
 cold. 
 
 •Lowell Obser7atory BuUetin No. 13. '!~ 
 
What We Know About Mars 148 
 
 A curious feature of the canals and other mark- 
 ings is that they do not always present the same ap- 
 pearance at the same equivalent time in successive 
 Martian years. Thus, a certain marking called by 
 Schiaparelli "Lacus Mceris" could not be found at 
 all at Arequipa in 1892. After an interval of thir- 
 teen years since it had last been seen, it reappeared 
 with perfect distinctness in 1903, and was observed 
 by Lowell.^'* A very marked change in the Deuca- 
 lionis Regio, observed in 1892 in connection with 
 the melting of the ice-cap, did not take place again 
 at the same equivalent season in 1894* ; nor has it 
 been observed since. A certain canal observed by 
 Schiaparelli was not found at all by Lowell, an- 
 other one having replaced it. This latter only re- 
 cently disappeared, Schiaparelli's original canal hav- 
 ing taken its place. 
 
 IS THE PLANET INHABITED BY INTELLIGENT BEINGS? 
 
 There is little doubt now that Mars possesses vege- 
 table, and perhaps animal life, but the question that 
 interests humanity is, Are there intelligent beings 
 there? The only important argument in favor of 
 their existence is the presence of the canals. These 
 canals are so long and narrow, straight and uni- 
 form, that they look artificial. If they are artificial, 
 " Lowell Observatory BuUetin No. 8. 
 
144 Man 
 
 it is certain that their constructors possess a knowl- 
 edge of spherical trigonometry, and considerable skUl 
 in the mechanical construction of surveying instru- 
 ments, implying greater intelligence than that pos- 
 sessed by our ancestors a thousand years ago. It is 
 doubtful if our progenitors in the year 900 A. D. 
 could have built a perfectly straight road three 
 thousand miles long, directed to a definite point, 
 even if it had been across level country. 
 
 But is the evidence sufficient as yet to warrant us 
 in pronouncing in favor of such intelligent beings? 
 Doubtless the temptation to do so is very strong, but 
 that should not influence our judgment. It is a gen- 
 eral principle of science that when two explanations 
 of a phenomenon are possible, we should, other things 
 being equal, choose the simpler. Lowell's maps of 
 Mars look very artificial but we must remem- 
 ber that they are composites of many drawings, such 
 as are given in this article. All the canals shown 
 on the maps are not seen at once; on the contrary, 
 only a very few of them are visible on the same night. 
 It seems to the writer that the arguments both for 
 and against intelligent inhabitants have been mate- 
 rially strengthened during the past few years. It 
 does not seem to him, however, that on either side 
 are they conclusive. The reader must therefore 
 choose for himself between them. 
 
 Let us suppose that there are intelligent inhabi- 
 
iUit 
 
 
 
 £ S i 
 
What We Know About Mars 145 
 
 tants. One can imagine, in the seasonal transfer of 
 the water across the equator, that a portion of the 
 moisture, condensed from the air each night as a 
 heavy dew, is deposited on the ground and perhaps 
 on sparsely growing and therefore invisible vegeta- 
 tion, in the desert regions. From that rare atmos- 
 phere, consisting largely of aqueous vapor, so much 
 may be condensed in the more elevated areas as to 
 flow in invisible channels to the larger canals, caus- 
 ing the vegetation there to develop, and thus become 
 visible. A good deal of the moisture would sink 
 into the soil, but this would the next day be eva- 
 porated by the Sun's heat, and continue on its course 
 to the winter pole. This explanation, of course, does 
 not necessarily involve the existence of intelligent in- 
 habitants ; but without them the canals would almost 
 certainly in the course of time lose their straight- 
 ness and artificial aspect. 
 
 The other explanation of the canals is that they 
 are due to the same causes that produce those on 
 the Moon. As seen through the telescope they look 
 exactly like them, save that the Martian canals are 
 much longer and somewhat wider. The lunar canals 
 seldom exceed ten miles in length. They radiate from 
 small lakes and join large seas precisely like the 
 Martian areas, and are equally straight and artificial 
 looking in appearance. They wax and wane with the 
 seasons in the same way. The Moon is so near that 
 
146 Mars 
 
 we can study them to advantage. The foundations 
 of the lakes are minute craterlets ; of the canals, fine 
 cracks. As the season progresses, dark areas form 
 about them and later fade out. The explanation 
 offered is that moisture is given out by the cracks, 
 which is later absorbed. This moisture nourishes 
 the vegetation to which the darkening is due. Ex- 
 actly similar cracks, causing similar vegetational ca- 
 nals, are found in Hawaii. One characteristic canal 
 was estimated by the writer at two or three yards in 
 width, by thirty in length. The terrestrial and lu- 
 nar canals are certainly produced without intelli- 
 gent assistance. 
 
 In conclusion, we may say that while we have not 
 as yet sufficient information to settle this ques- 
 tion definitely, information is slowly accumulating, 
 largely owing to Professor Lowell's indefatigable in- 
 dustry, which win doubtless decide it in time. His 
 observatory is the only one at present specially de- 
 voted to securing an answer to it, and it seems al- 
 most a pity that some other favorably located obser- 
 vatory should not devote some of its time to the 
 same object. 
 
CHAPTER XIV 
 
 DIFFERENT EXPLANATIONS OF THE 
 CANALS OF MARS ^ 
 
 Leaving aside the older and now generally dis- 
 credited explanations that the canals are gigantic 
 water channels, that they are cracks in a universal 
 covering of ice, and that they are grooves cut by 
 colliding asteroids, we will turn to the explanations 
 held as more probable by the astronomers of the 
 present day. 
 
 Much of the oldest of these ^ considers them to 
 be caused by narrow ditches, which, crossing the 
 desert regions of the planet, furnish water to vege- 
 tation growing along their banks. It is these com- 
 paratively broad bands of vegetation, and not the 
 narrow water-channels themselves, which are visible 
 in our telescopes. The chief advocate of this view 
 at the present time is Professor Lowell, who has 
 adopted it as the foundation of his theories of 
 Martian civilization. A serious objection to the 
 
 •Harper's MontMy, 1908, 193. 
 " Science, 1888, 12, 83. 
 
 147 
 
148 Mart 
 
 hypothesis is the difficulty of forcing water through 
 the canals for thousands of miles, over a compara- 
 tively level country. Professor Lowell gets over this 
 difficulty by stating that it is pumped through them 
 artificially. Many astronomers recoil from an arti- 
 ficial explanation, where it is possible to account 
 for the phenomena observed by any natural method. 
 The difficulty of transporting the water is fur- 
 ther enhanced if we consider the fact, which is gen- 
 erally admitted, that the amount of atmosphere we 
 find on Mars does not exceed one-quarter the quan- 
 tity per square mile of surface that we find upon 
 the Earth. This view is based largely on Professor 
 Campbell's spectroscopic investigations, confirmed 
 by the clearness with which we see the details of the 
 planet's surface. Since gravity upon Mars is but 
 three-eighths of what it is upon the Earth, the 
 atmospheric pressure on the Martian surface can- 
 not exceed three thirty-seconds of our own, or 71 
 miUimeters of mercury. Under this low pressure 
 water boils at 113° Fahr. If the amount of atmo- 
 sphere on Mars is only one-tenth as much as that 
 on the Earth, which is highly probable, the boHing 
 point of water upon the surface of the planet would 
 be reduced to 84° Fahr. That the daylight tem- 
 perature of the surface does not differ greatly from 
 our own, we know by the rapidity with which the 
 polar ice-caps disappear on the approach of sum- 
 
Different Explanations of the Canals 149 
 
 mer. It would, therefore, seem that the evaporation 
 of water from the surface must proceed with extra- 
 ordinary rapidity, and the difficulty of transporting 
 it through canals, and supplying sufficient for the 
 needs of vegetation upon the way, must be accord- 
 ingly greatly enhanced. 
 
 Indeed, it would seem nedessary to substitute 
 gigantic water-mains for the canals, with a most 
 extended system of supplementary piping. The 
 amount of power requii'ed to pump sufficient water 
 to irrigate anywhere between 100,000 and 1,000,000 
 square miles of surface, through such a system of 
 piping, may be left to any competent hydraulic 
 engineer to compute, with the added statement that 
 most of the water is to be transported to a distance 
 exceeding 1,000 miles. 
 
 If we are to insist on a Martian civilization at 
 all hazards, a more defensible explanation of the 
 canals might be founded on the photograph shown 
 in Fig. 1. This photograph was obtained by the 
 writer during the past summer while on a vacation 
 trip in the Azores. It represents a somewhat insig- 
 nificant hill known as Cabefo Gordo, which was 
 passed on the way to the summit of the volcano 
 Pico, near Fayal. 
 
 There is a bush or low tree, known as the urze, 
 which grows on the slopes of the volaano, and 
 which is analogous in character to our pines and 
 
150 Mars 
 
 spruces. This hill was originally covered with it, 
 but most of it has now been cut down by the shep- 
 herds in order to afford pasturage to their flocks. 
 Narrow areas of it have been permitted to stand, 
 however, in order to furnish protection to the ani- 
 mals against the terrific winter winds sometimes 
 occurring at these altitudes. 
 
 Similar markings might very readily be produced 
 artificially on Mars, and we are not even obliged to 
 assume that any portion of its surface is of a desert 
 character. It must be remembered that the canals 
 of Mars are not a few feet but several miles in 
 breadth. Imagine that the whole surface of the 
 planet was originally covered with some form of 
 bush or tree, which in the northern and equatorial 
 regions has now been largely destroyed. Its con- 
 tinued presence in the southern regions would ac- 
 count for the so-called seas, while narrow, more or 
 less continuous, strips of it would account for the 
 canals. 
 
 The vegetation, both field and woodland, would 
 be supported by the atmospheric circulation, just 
 as it is upon the Earth, and no gigantic engineering 
 feats whatever are required of the assumed inhab- 
 itants. Why the inhabitants of Mars should grow 
 their vegetation in these peculiar forms, the writer 
 does not pretend to know, but very likely the same 
 reason that influences the shepherds of Cabe9o 
 
FIG. 1. (:abe(;(j (.;(.>kdo, a hill i.v thk a/ores, SH0A\'IXG caxal- 
 
 HKE MAHKIXGS 
 
 FIG. O. A CANAL-LIKE MARKING PHODUGED NATURALLY IN THE 
 DESERTS OP HAWAII BY AN ACTIVE STEAM-CRACK 
 
iDijferent Explanations of the Canals 151 
 
 Gordo, protection against severe winter climate, 
 may be the explanation. 
 
 But is it necessary to assume a Martian civiliza- 
 tion? Astronomers generally think not. The only 
 argument in its favor is the artificial appearance 
 of the drawings of the canal system of the planet. 
 What the public generally does not understand, 
 however, is that while the drawings may look thor- 
 oughly artificial, and may be most carefully made, 
 yet that the planet itself, if sufficiently well seen, 
 might not look artificial at all. The statement 
 sometimes made that the canals really consist of 
 straight uniform lines is by no means generally 
 accepted by astronomers. In fact, as we shall pres- 
 ently see, what evidence we have points quite in 
 the opposite direction. 
 
 ■ iiiiiiiieHi^ 
 
 Fig. 2. A Series of Dots Which at a Distance of 30 Feet 
 Looks Like a Continuous Line 
 
 If we make a hoi'izontal row of dots or vertical 
 lines on a piece of paper (Fig. 2), the distance be- 
 tween their centres being one-eighth of an inch, and 
 if we view them from a distance of thirty feet, they 
 will appear to our eyes simply as a continuous, 
 uniform, horizontal line. If we scatter a sufficient 
 number of dots and lines irregularly over the paper 
 
152 
 
 Mars 
 
 (Fig. 3), and view tliem also from a distance of 
 thirty feet, it will be possible for us, after a careful 
 examination, to see the three chief dots connected 
 as shown by the heavy lines, (Fig. -A). At a suitable 
 distance these lines will appear perfectly straight 
 and uniform. If we approach somewhat nearer, the 
 finer Hnes wiU appear. These lines have a very 
 artificial aspect, and yet, if we view the original 
 (Fig. 3) close at hand, we shall see that the drawing 
 reaUy represents notlung but an irregular grouping 
 of spots. 
 
 Photographs of fine planetary or lunar detail 
 are much more unreUable than drawings, because 
 they have to be on so small a scale in proportion 
 to what is known to pliotographers as the "grain" 
 
 
 # 
 
 
 ff. / -V- 
 
 FiGS. 3 AJTD 4. Irrf.gxjt.ab Mahexs"gs Sttch as Abe Showk dt 
 Fig 3, Whex See:s from a Distance of 30 Feet, Re- 
 SEiiBLE the Casals of Fio. 4 
 
Different Explanations of the Canals 153 
 
 of the plate. This grain is a sort of irregular back- 
 ground, which becomes very conspicuous as soon as 
 the plate is sufficiently enlarged. Atmospheric diffi- 
 culties and irregular motions of the driving-clock 
 of the telescope are also much more serious to the 
 photographer than to the visual astronomer. For 
 these reasons astronomers generally consider, that 
 it was a great triumph for the photographers of the 
 Lowell Observatory to be able to get any indica- 
 tions of the canals whatever upon their plates. As 
 far as a detailed study of the planet's surface is 
 concerned, however, the Lowell drawings are of much 
 more value than the Lowell photographs. 
 
 As to the so-called doubling of the canals, most 
 astronomers simply decUne to admit the existence 
 of the phenomenon, on the visual and photographic 
 evidence so far presented. That out of several hun- 
 dred canals one or two might be double from merely 
 accidental causes is not denied, but the demonstra- 
 tion of the duplication of any large proportion, 
 such as one-fourth, as claimed by Professor Lowell, 
 is awaited with interest. 
 
 But if we deny that the canals are artificial, how 
 then can they be explained.'' The alternative hypo- 
 thesis,^ and the one which it is believed from the 
 writer's private correspondence is generally pre- 
 ferred by those astronomers interested in Mars, is 
 
 " Popular Astronomy, 1904, 13, 439. 
 
154 Mars 
 
 that the canals are due to volcanic cracks lying 
 between craterlets on the Martian surface. Water 
 vapor escaping from these craterlets and cracks 
 nourishes the vegetation growing along their sides, 
 and it is this vegetation which is visible in our tele- 
 scopes. 
 
 This latter view has the distinct advantage that 
 it also explains the canals on the Moon, which, as 
 seen through a small telescope, are indistinguishable 
 from those on Mars. They also go through the 
 same changes and transformations in the course of 
 a lunation that the Martian canals do in the course 
 of the Martian year, and differ from them only in 
 the fact that they are on a much smaller scale. 
 Through a large telescope, with good atmospheric 
 conditions, the craterlets and cracks about which 
 the lunar lakes and canals are formed can be dis- 
 tinctly seen, and the gradual transformation of a 
 crack into a canal has been watched, and the rate 
 of growth of the latter measured.* Through a 
 small telescope the lunar canals, like the Martian 
 ones, appear straight and perfectly uniform. 
 Through a large glass, on the other hand, irregu- 
 larities of outline appear, and marked variations 
 in the depth of color. 
 
 Similar natural canals formed about terrestrial 
 
 * Annals Harvard College Observatory, 53, 78. Memoirs 
 American Academy, 1906, 13, 176. 
 
Different Explanations of the Canals 155 
 
 volcanic cracks have been studied and photographed 
 in Hawaii. See Fig. 5.^ This view represents a por- 
 tion of the desert extending to the south of KUauea. 
 The only vegetation growing upon it consists of 
 trees, low bushes, and ferns, which stretch across 
 it in long, narrow, straight lines, following the course 
 of the steam cracks, whose exhalations furnish the 
 necessary moisture on which the existence of the 
 vegetation depends. 
 
 Stretching across Fig. 6 is shown the Ariadaeus 
 rill, a volcanic crack upon the Moon 150 miles in 
 length. If it were still giving out steam, we should 
 doubtless have here a straight lunar canal quite 
 comparable in size to many of those found on Mars. 
 About one thousand of these riUs, most of them 
 much smaller than this one, are now catalogued 
 upon the Moon. 
 
 The objection that most astronomers feel to the 
 admission of the existence of civihzation upon Mars 
 is not, it seems to the writer, a sort of jealousy of 
 the other planets, such as Professor Lowell has sug- 
 gested and a wish that intelligence should be con- 
 fined to our Earth. On the contrary, trustworthy 
 evidence of its existence would certainly be welcomed 
 by them, as by everyone else, not only with pleasure, 
 but with wild enthusiasm. Their feeling, I believe, 
 is rather that the four planets, Venus, the Earth, 
 
 ' See Figure 5, facing p. 150. 
 
156 Mars 
 
 the Moon, and Mars, are all of about the same size 
 and are situated at similar distances from the Sun. 
 Their surface conditions must therefore bear a gen- 
 eral resemblance to one another. Life is so per- 
 sistent, and will exist under such varied conditions, 
 that it is not surprising that it should be found on 
 aU of them. Indeed, as we have seen, we have already 
 pretty strong visual evidence that it does exist on 
 two of them besides the Earth. As compared with 
 vegetation, it seems probable that human life, or its 
 planetary equivalent, would have much more nar- 
 row limits. Vegetable life beneath the sea, for in- 
 stance, is, as we all know, very luxuriant. The pos- 
 sible limits of civilization are still more narrow than 
 those of human life. 
 
 Under the reduced atmospheric pressure and 
 probable almost total lack of free oxygen upon 
 Mars, we can stiU see no reason why vegetation 
 should fail to exist. But is it likely that civilization 
 should be found there also.'' We do not definitely 
 deny that some form of civilization under these cir- 
 cumstances might be possible, but why invoke its 
 aid to explain the various observed phenomena, such 
 as the canals, if we can furnish a better, or even 
 nearly as good, explanation of them by some other 
 hypothesis.'' 
 
 The physical conditions on Mars are in many 
 ways intermediate between those found upon the 
 
Different Explanationt of the Canals 187 
 
 Earth and the Moon, and it seems plausible that 
 the life existing upon it should similarly be of a 
 higher type than that found on the Moon, and of 
 a lower type than that found at present on the sur- 
 face of the Earth. Even if the physical conditions, 
 as we understand them, were equally favorable with 
 those on the Earth, civilization would by no means 
 be a necessary consequence. Had it not been settled 
 by Europeans, the United States would still be a 
 wilderness. How much less should we hasten to 
 accord civilization to a planet of which we know 
 little, except that if we were transported there our- 
 selves, we should instantly die. 
 
CHAPTER XV 
 SIGNALLING TO MARS * 
 
 Although this computation was first made by the 
 writer for his own amusement, nearly twenty years 
 ago, it had never seemed to him of sufficient interest 
 or importance to the astronomical world to publish 
 it anywhere, and he would not do so now, had not 
 his definite statements on the subject been directly 
 called in question. By the term "possibility of com- 
 munication with a remote planet" the writer means 
 that if a portion of the human race, with their pres- 
 ent knowledge and appliances were removed to that 
 planet, and could live there, that it would be pos- 
 sible to communicate with them. Whether there are 
 intelligent beings on Mars or on any other planet, 
 the writer does not know. That is an entirely sep- 
 arate question, and has nothing whatever to do with 
 the case. 
 
 The constants required in our computation are as 
 follows : — 
 
 > Popular Astronomy, 1909, 17, 495. 
 158 
 
Signalling to Mart 169 
 
 »S'=Mean distance from the Earth 
 
 to the Sun 92,900,000 miles 
 
 M^Mean distance of Mars to the 
 
 Sun 141,500,000 mHes 
 
 ZJ^Mean diameter of the Sun 
 
 from the Earth 1,922" 
 
 i^Stellar magnitude of the 
 
 Sun -26.83 miles 
 
 The computation is made when Mars is situated 
 in quadrature with the Sun. In this position its 
 mean distance from the Earth, M, is 108,000,000 
 miles. Let us imagine a mirror erected upon the 
 Earth of such a size that the whole disk of the Sun 
 can be seen in it from Mars. Let d be the diameter 
 of the Sun as seen in the mirror, and I its magni- 
 tude. Then, 
 
 DS 
 
 d = = 888" 
 
 S -^M 
 and 
 
 1 = 2.5 (log (S+My— log S^)-{-L= —25.15 
 
 Let us now imagine this mirror so reduced in size 
 as to reflect a circular beam whose diameter is only 
 J Po^ ^jpQ of that of the Sun's disk. As seen 
 
 from Mars the diameter of this beam wiU be 
 
160 Man 
 
 0". 00089, and its brightness, which will be reduced 
 30 magnitudes, 4.85. The diameter on the Earth of 
 such a beam will be a trifle less than half a mile. 
 Therefore, allowing for absorption and an inclined 
 mirror, the sunlight reflected from an area of mir- 
 rors a Kttle over half a mile square would appear to 
 Mars, when in quadrature, of the brightness of a 
 star of the fifth magnitude. When Mars was forty- 
 five degrees from opposition, and its distance from 
 the Earth was 61,000,000 miles, such a beam would 
 be brighter than the fourth magnitude. 
 
 This light would, of course, be very conspicuous 
 from Mars with the naked eye, were it not for the 
 brightness of the Earth itself. This materially modi- 
 fies the problem. By holding a mirror so as to cover 
 half of the area of a 6-inch objective, and by so 
 doing projecting the image of a, star of the 2.8 mag- 
 nitude upon the disk of the Moon, the star was 
 found to be just visible with a 2.5-inch eye-piece. 
 With a higher power and steadier mirror, much bet- 
 ter results would have been obtained, but on this 
 basis a 24-inch objective should be able to show a 
 star of the 6.5 magnitude when projected upon the 
 disks of the Earth or Moon. The object of using 
 a higher power would be to reduce the light of the 
 Moon without diminishing that of the star. With 
 four times the power, a signal of the 8.0 magnitude 
 
Signalling to Mars 161 
 
 should readily be detected, even after allowing for 
 some magnification of the star image itself. 
 
 It therefore appears not only that the plan of sig- 
 nalling to Mars by the system proposed is "scien- 
 tifically plausible," but that if it were adopted, we 
 should produce a signal that would be three to four 
 magnitudes, that is 16 to 40 times brighter than 
 necessary, and would, therefore, be dazzlingly con- 
 spicuous to Martian observers, if they were intel- 
 lectually and physically our equals. 
 
 In closing, the writer would only add that this 
 plan of signalling to Mars is not now, and never has 
 been (as is shown by a large portion of the con- 
 temporary press), advocated by the writer, until 
 after we shall have obtained more definite informa- 
 tion that there are intelligent inhabitants upon Mars. 
 
CHAPTER XVI 
 THE CANALS OF MARS ^ 
 
 In the issue of the Scientific American of July 
 10th, a correspondent argues that the discovery of 
 the gradual shifting of position of some of the canals 
 of Mars helps to strengthen, instead of weakening, 
 the theory of irrigating ditches. It does undoubtedly 
 strengthen aU the theories of the canals based on 
 the idea that they are strips of vegetation, and it 
 also incidentally strengthens the idea that their for- 
 mation and maintenance may be due to the efforts 
 of intelligent life upon the planet. But it weakens 
 the explanation of irrigating ditches, as compared 
 with some of the other theories. 
 
 Let us now consider some of these, which assume 
 the existence upon Mars of intelligence analogous 
 to our own. Let us first discuss one of those based 
 on the idea that the lack of water is really the chief 
 necessity felt upon the planet. According to this 
 theory, invisible water vapor is evaporated by the 
 heat of the sun from the snowy pole in the spring- 
 
 ' Sdentiflc Amtrieaa, 1915, US, 340. 
 162 
 
The Canals of Mars 163 
 
 time and transported by the planetary circulation 
 to the other pole, where the sun is setting for the 
 long winter night. Here the vapor, which forms a 
 much larger proportion of the planet's atmosphere 
 than with us, is condensed as snow, a constant dis- 
 tillation going on by the sun's heat from one pole 
 to the other, and then back again, every year. 
 During the nighttime a portion of this traveling 
 vapor is deposited as fog over the level regions. In 
 many cases these elongated areas may lie in slightly 
 depressed regions or valleys, where the fog would 
 naturally accumvdate of itself. In the early morn- 
 ing on Mars, where the sun is rising, we can some- 
 times see the fog clear away, and it is in these 
 moistened regions that the vegetation springs up and 
 forms the so-called canals. 
 
 But while the lack of water appears at first sight 
 to be the chief necessity of Mars, judged by terres- 
 trial standards, yet such may not really be the case 
 at aU, and we might suggest that other needs may 
 be much more pressing. Besides water, vegetation 
 requires several solid constituents, the chief of which, 
 applied as fertilizers, are alkalies, phosphates, and 
 nitrates. On account of its small atomic weight, 
 nitrogen in the gaseous form must certainly be 
 rather rare on Mars. We are just beginning on the 
 earth to have to use our atmospheric nitrogen as 
 a source of nitrates for fertilizers. It may easily be 
 
164 Mart 
 
 that the Martians have not suflBcient quantities of it 
 or of some other of these solid constituents to en- 
 able them to fertilize the whole surface of their 
 planet, and they therefore distribute their fertilizer 
 as widely as they can in those places where it will 
 do the most good, occasionally shifting their crops 
 to fresh regions of the planet. 
 
 Still another theory, also involving artificial direc- 
 tion, may be based on the fact that, besides solids 
 and water, vegetation requires two gases for its 
 existence — oxygen and carbon-dioxide. While a very 
 important part of the work of plant life is the break- 
 ing up of the latter gas and the evolution of free 
 oxygen, yet oxygen is itself consumed in considerable 
 quantities by vegetation, just as it is by animals. 
 We know that there is not very much atmosphere 
 on Mars, and oxygen must be scarce. 
 
 But, besides the oxygen, it is quite possible that 
 the carbon-dioxide, too, may be lacking. On our 
 own earth this necessary food for vegetation is pro- 
 vided, not as is sometimes supposed, chiefly by the 
 breathing of the animal world, but by our more or 
 less active volcanoes. Animal life, indeed, furnishes 
 only an insignificant fraction of the total supply. 
 Mars is an ancient world, and any volcanoes that it 
 formerly possessed may now very likely be entirely 
 extinct. In such a case all the carbon-dioxide re- 
 quired by vegetation must be supplied by the animal 
 
The Canals of Mars 165 
 
 world, by combustion, or possibly by some other 
 chemical process. To maintain the proper balance 
 between animal and vegetable life, it is clear that 
 the latter must be more or less limited. All useless 
 vegetation would be destroyed, and such as was left 
 would only be permitted to grow in the most favor- 
 able and necessary places. Indeed, we find that the 
 canals which when they first appear are very wide, 
 gradually narrow as the season progresses, and this 
 very narrowing may itself be a visible indication to 
 us of the activities of the Martians ! 
 
 It is generally believed that the southern hemi- 
 sphere of Mars is situated at a slightly lower level 
 than the northern one. This is indicated by observa- 
 tions of the Martian terminator. This difference 
 of level has been given as the explanation for the 
 observed fact that most of the Martian vegetation 
 is confined to the southern hemisphere. This expla- 
 nation would be particularly applicable if there were 
 a shortage of carbon-dioxide on the planet, as it is 
 well known that this gas always tends to collect, on 
 account of its high specific gravity, in any deep 
 depressions of the earth's surface. 
 
 Each one of these theories accounts for the canals 
 found upon the planet and for their distribution 
 chiefly in the northern hemisphere, as well as for 
 their shifting and narrowing with the progress of 
 the seasons. If we once admit the existence of intel- 
 
166 Mars 
 
 ligent life on Mars, since we have no means what- 
 ever of knowing what are their chief needs, it be- 
 comes useless for us to theorize further upon their 
 reasons for constructing the canals, otherwise than 
 to say that they indicate a shortage of supplies for 
 vegetation. 
 
 Whichever need may be most felt, whether water, 
 nitrogen or carbon-dioxide, it appears that the can- 
 als are calculated to meet it, and are what we might 
 ourselves construct or plant under similar circum- 
 stances. 
 
 All of these theories avoid the necessity of enor- 
 mous conduits and the expenditure of an amount of 
 work in pumping, which has recently been estimated 
 by an expert adherent of the pumping hypothesis 
 at 2,500,000,000 horse-power, or four thousand 
 times that of Niagara Falls. 
 
 The reason that the writer stated in a former 
 paper, that the irrigation conduit theory was not 
 strengthened by the shifting the canals, was that 
 the number of conduits would have to be increased 
 if the canals shifted. This does not, of course, dis- 
 prove the conduit theory, but certainly does not 
 strengthen it, as compared with the other theories 
 explaining the canals, where no such added construc- 
 tion is necessary. 
 
CHAPTER XVII 
 MARS— THINGS KNOWN AND SURMISED ^ 
 
 It is a rather diiBcult matter to distinguish what 
 is known from what is surmised about any subject, 
 but if we define what is known about Mars as mean- 
 ing what is generally believed about it by profes- 
 sional astronomers, and what is surmised as what at 
 the present time seems most probable, the writer 
 thinks that present Martian views may be summar- 
 ized rather briefly. 
 
 We have, first, the astronomical data, which are 
 certainly known, and are approximately as follows: 
 The distance of the planet from the sun is one and 
 a half times as great as that of the earth. Its year 
 is 687 of our days, or nearly two of our years. Its 
 orbit is very eccentric, so that it is sometimes much 
 nearer to the sun than at others. Its diameter is a 
 little over forty-two hundred miles. Its mass is one- 
 ninth, and its surface gravity about two-fifths, that 
 of the earth. This latter quantity is most impor- 
 tant in determining its supply of water and atmos- 
 ' CosmopoUtan, Oct., 1909, 616. 
 167 
 
168 Mars 
 
 phere, and therefore its habitability. The inclina- 
 tion of its equator to its orbit is practically the same 
 as that of the earth. Hence its seasons are similar, 
 except that they are nearly twice as long as our own. 
 Its period of rotation upon its axis, that is to say, 
 its day, expressed in terrestrial units, is twenty-four 
 hours and thirty-seven minutes. 
 
 Most astronomers would probably accept the fol- 
 lowing statements as true : The planet possesses white 
 polar caps, which increase in winter and diminish 
 in summer. These are due to ice. When they are 
 melting most rapidly they are surrounded by a dark 
 ring of water, which soon disappears. This is the 
 only water visible upon the planet. The melting ice 
 fixes the temperature at this time, which is 32° 
 Fahrenheit. The atmosphere is extremely rare. 
 This involves great extremes of temperature, a rapid 
 evaporation of the water in the daytime, and a very 
 rapid deposition of dew or frost at night. The 
 climate from our standpoint must, therefore, be ex- 
 tremely disagreeable, even at the equator. While 
 never very hot, it must at night be extremely cold. 
 The atmosphere is much more rare than upon our 
 highest mountain summits, and would, therefore, be 
 quite unbreathable by terrestrial animals. Clouds 
 have been observed floating over the surface of the 
 planet, and their speed and direction measured. Ex- 
 cept at sunrise and sunset they are of rare occur- 
 
Mars — Things Known and Surmised 169 
 
 rence, although they are observed more frequently 
 at the time of the melting of the polar caps. 
 
 The dark surface markings of the planet consist 
 of the so-called seas, canals, and lakes, which last 
 are also known as oases. The light surface mark- 
 ings consist of the so-called deserts, causeways, and 
 white spots. Those astronomers who attempt to ex- 
 plain them at all consider them to represent diiFer- 
 ent densities of vegetation. The writer believes the 
 white spots to be due to a form of vegetation equiva- 
 lent to our flowering plants. These spots appear for 
 a few weeks in the summer time near the tropics. 
 
 The above summarizes practically all that we 
 know, and all that we may properly surmise, with 
 regard to Mars. To those who are in any way in- 
 terested in the planet, the matter of most vital im- 
 portance, at present, is the question, Are any of these 
 surface markings artificial.'' Certainly they may be. 
 We have no definite proof to the contrary, but any 
 statement at the present time ascribing them di- 
 rectly to intelligent beings must be clearly under- 
 stood to be no better than a speculation. 
 
 What then can we do to settle this question.? To 
 many persons this is a matter of serious importance. 
 All who have seen the canals clearly, must admit that 
 they have an artificial aspect. That is to say, they 
 are not sinuous in shape, but are fairly straight. 
 Moreover, they are of pretty uniform breadth and 
 
170 Mars 
 
 density. This would all appear very favorable to 
 an artificial origin, but unfortunately it so hap- 
 pens that there are canals upon the moon which 
 appear equally straight and equally artificial, al- 
 though much smaller. They also appear and dis- 
 appear with the seasons. The lunar canals certainly 
 cannot be artificial. Similar canals on a stiU smaller 
 scale have been found in the Hawaiian Islands. They 
 are due to vegetation along volcanic cracks crossing 
 a desert region. The steam emitted from these 
 cracks supports the vegetation, which would other- 
 wise wither and die. The question at once arises 
 whether it is possible that the lunar and Martian 
 canals are due to this same cause. 
 
 Few astronomers now deny the existence of the 
 Martian canals. The question for us to settle is not. 
 Do they exist.? but. How do they look.'' To settle 
 this does not require a gigantic telescope, but it does 
 require an especially good atmosphere. Such an 
 atmosphere can only be found in a low latitude. A 
 five-inch telescope in Jamaica shows much finer 
 planetary detatil than a fifteen-inch telescope in 
 Cambridge. A large telescope erected in our north- 
 ern states would be absolutely useless for the pur- 
 pose in hand. Indeed, it would probably be unde- 
 sirable in any location. Perhaps the best results 
 would be obtained with a moderate-sized telescope of 
 about twenty-four inches aperture, which is the size 
 
Mars — Things Known and Surmised 171 
 
 of the instrument which has been erected by Prof. 
 Percival Lowell in the clear atmosphere of Flagstaff, 
 Arizona. Given such an instrument in an ideal lo- 
 cality, how should it be used? 
 
 A man who has good eyesight, or who is a skUful 
 astronomer, is not necessarily a good artist. This 
 poiat has been quite overlooked by the public hith- 
 erto. Yet it is of the utmost importance if we wish 
 to know exactly how the canals appear. To settle 
 this question a number of experienced astronomers 
 should be invited to sketch the canals as seen by 
 them through this same telescope, located under 
 these extremely favorable conditions. Astronomers 
 with some little experience in sketching planetary or 
 lunar details should be selected by preference. Be- 
 sides the astronomers, a number of artists skilled in 
 miniature work should also be invited to study the 
 planet. Probably none of these men would secure 
 results of much value during the first week of their 
 observations, because it requires a special training 
 acquired only by practice to enable one really to un- 
 derstand what he does see in this class of work. Dur- 
 ing the second week of this work, however, more valu- 
 able results would be secured. 
 
 Studies of both the lunar and Martian canals 
 should be made by each observer, and finally the best 
 results of each man should be selected and published. 
 When this has been done, then not only astronomers, 
 
172 Mars 
 
 but the public at large, will have a fair opportunity 
 to judge for themselves of the appearance of the de- 
 tail of the planet, and decide whether or not it is 
 probable that the canals of Mars are the work of 
 intelligent beings. This is certainly the next step 
 that should be taken in our investigation of this most 
 interesting planet. 
 
INDEX 
 
 Associated observers, 19. 
 --Atmosphere, 12, 20, 59, 126, 
 148. 
 
 Blue color of water, 40, 43, 48, 
 
 57, 99, 100. 
 
 Canals, Description of, 83, 86. 
 Duplication, 68, 67, 89, 113, 
 
 138, 153. 
 Explanation of, 14, 42, 43, 
 
 58, 76, 87, 95, 103, 108, 
 111, 133, 138, 145, 147, 149, 
 162, 170. 
 
 Lunar, 105, 109. 
 Shifting, 18. 
 
 Width of, 19, 84, 89, 104, 
 134. 
 -Changes visible, 18, 39, 42, 48, 
 58, 84, 97, 99, 142. 
 Climate, 13, 78. 
 Clouds, 13, 17, 55, 57, 68, 60, 
 
 128, 130. 
 Color changes, 38, 46, 57, 81, 
 
 100, 118. 
 Colors visible, 18, 26, 45, 57, 
 79. 
 
 Data regarding planet, 11, 120, 
 
 167. 
 Depressions on terminator, 
 
 101. 
 Deserts, 14, 45. 
 
 EUipticity of disc, 59. 
 
 Facts regarding planet, 11, 
 57, 120, 167. 
 
 History of discoveries, 64, 131. 
 Horse power for irrigation, 15, 
 166. 
 
 takes, 19, 58, 62, 83, 86. 
 
 Lunar, 109, 137, 145. 
 Life, Intelligent, 92, 143, 166, 
 164. 
 
 Marshes, 12, 17, 81. 
 Meteorology, 78. 
 
 Photographs of planet, 129, 
 
 135. 
 Polarization, 43, 99. 
 
 Seas, 14, 44, 72, 79, 124. 
 Signalling to Mars, 158. 
 Snow, 12, 21, 32, 46, 60, 68, 
 116, 124. 
 
 Telescopic apertures, 131, 170. 
 Temperature, 24, 75, 127. 
 
 Vegetation, 14, 43, 46, 101, 108, 
 130, 133, 134, 142. 
 
 Water transferred across 
 planet, 15, 74. 
 
 173