Cornell University 
 Library 
 
 The original of tiiis book is in 
 tine Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924031363157 
 
DEPARTMENT OF COMMERCE AND LABOR 
 
 BUREAU OF STANDARDS 
 
 S. W. STRATTON . . Direcliit 
 
 ^;^ „..-*» 
 
 U I, 
 
 THE NATIONAL ^^^ 
 OF STANDARDS 
 
 ■■•■'>'■, 
 
 WASHINGTON 
 
 GOVERNMENT PRINTING OFHCE 
 
 1911 
 
DEPARTMENT OF COMMERCE AND LABOR 
 
 -uc ^ BUREAU OF STANDARDS ^n^ao. . f ^V.. -vic l&j 
 : S. W. STRATTON . . Ditectoi 
 
 THE NATIONAL BUREAU 
 OF STANDARDS 
 
 WASHINGTON 
 
 GOVERNMENT PRINTING OFRCE 
 
 1911 
 
CONTENTS. 
 
 Pago. 
 
 Introduction 5 
 
 Length 7 
 
 Mass 8 
 
 Volume 8 
 
 Density 9 
 
 Trade we^hts and measurea 9 
 
 Barometry 10 
 
 Time 11 
 
 Electricity 11 
 
 Electrical units (international) 11 
 
 Electric resistance 12 
 
 Electric current 12 
 
 Electromotive force 12 
 
 Absolute electrical units 12 
 
 Electric conductivity 13 
 
 Electric capacity and inductance 13 
 
 Electric instruments 14 
 
 Magnetism 14 
 
 Photometry 15 
 
 Electrolysis 15 
 
 Heat and thermometry 16 
 
 Optics 18 
 
 Chemistry 19 
 
 Testing materials 19 
 
 Cement 20 
 
 Paper 20 
 
 Textiles 21 
 
 Miscellaneous materials 21 
 
 Engineering instruments 22 
 
 Engineering testing 22 
 
 Publications 23 
 
 Equipment 23 
 
 (3) 
 
THE NATIONAL BUREAU OF STANDARDS. 
 
 at 
 
 INTRODUCTION. 
 
 In 1901 the National Bureau of Standards was established by 
 Congress, with broad functions, consistent with the modern view 
 of standards and standard measurements. In 10 years the bureau 
 has grown to occupy an important place in the Government, hav- 
 ing 286 employees, four laboratory buildings in Washington, and 
 branch laboratories in Pittsburgh and Northampton, Pa., and in 
 Charleston, S. C. The main laboratories are located in the north- 
 western suburbs of Washington at an elevation of 350 feet above 
 the Potomac River, on a natural hill site of about 8 acres — a local- 
 ity admirably suited to its work. A fifth building is under construc- 
 tion for the electrical work of the bureau. As rapidly as consistent 
 with its standard of work the bureau has taken up the following 
 functions as prescribed in its organic act : 
 
 (1) The custody of the standards, which involves their care and 
 preservation and also the intercomparisons and researches necessary 
 to maintain the constancy of such standards as, are liable to change. 
 
 (2) The comparisons of standards for States, municipalities, in- 
 stitutions, and the general public — comprising standards used in 
 commerce, manufacturing, and science, assuring to the public accu- 
 racy at its source — in the factory and the works laboratory. 
 
 (3) The construction of standards as required by scientific or 
 technical progress. New standards are constructed at the bureau 
 upon the basis of the best available data, in some cases upon re- 
 searches at the bureau and sometimes by international agreement. 
 
 (4) Standardization of measuring apparatus for manufacturers 
 as a test of their output, or for the user that he may verify instru- 
 ments or materials independently. 
 
 (5) Technical research upon problems connected with standards, 
 problems arising constantly in all lines of testing and stardardiza- 
 tion. Such research facilitates scientific and technical progress, 
 since by refined measurements alone are many of these advances 
 made possible. 
 
 (6) Determination of physical constants, the measured data re- 
 lating to materials and energy which underlie scientific and tech- 
 
 (5) 
 
nical work. In such work direct reference to the standards is 
 highly desirable. 
 
 (7) Determination of the properties of materials for general use 
 in technology and trade. This work is based upon the modern view 
 that quality depends upon definite measurable properties, and it 
 therefore requires access to standard measuring apparatus and fa- 
 cilities for all kinds of measurements. 
 
 Weights and measures were once restricted to length, area, volume, 
 and weight. Within recent years, however, since power, electric cur- 
 rent, heat, light, irrigation, refrigeration, and services of other kinds 
 have entered the world's markets as commodities for production and 
 sale, the scope of weights and measures has broadened to include 
 such measures as those of velocity, pressure, energy, electricity, tem- 
 perature, and illumination. The importance of correct standards 
 and uniformity of measures is readily appreciated. Almost every, 
 industry has its units, its particular methods of measurement, and its 
 special measuring instruments. These instruments are designed for 
 every particular need, and their variety is evidence of the high state 
 of the art of measurement and its importance in industrial and 
 scientific work. Such instruments have so multiplied and the demand 
 has grown so rapidly that the manufacture of weights, measures, and 
 measuring instruments now forms in itself a whole group of indus- 
 tries. While the testing of standards and instruments is an impor- 
 tant part of the bureau's work, not less important is the research 
 conducted to improve standards and methods of measurement. Hence 
 it is necessary to maintain a force of men and an equipment for doing 
 scientific work of the highest grade. The bureau, as a court of highest 
 appeal in matters pertaining to measurement, must possess standards 
 as perfect as possible. Its methods and instruments must be the 
 best available, its laboratory facilities complete, and, finally, men of 
 good training and experience must be in charge of each line of work. 
 
 The standards of the bureau are made available for the service of 
 the public in several ways. First, the States of the Union have been 
 furnished by the Federal Government with sets of the metric and 
 customary standards, which from time to time may be reverified. 
 Standardizing facilities are thus afforded for local inspection of 
 trade measures. Secondly, tests are made of manufacturers' stand- 
 ards to enable them to maintain a high standard of accuracy in their 
 output. Finally, the general public submits to the bureau stand- 
 ards and measuring instruments for direct test at nominal fees. The 
 willing cooperation of State sealers and of manufacturers has re- 
 sulted in a steady, and in some cases rapid, improvement in indus- 
 trial standards and products. In each line of standardization the 
 cooperation of the manufacturers and technical experts was first se- 
 cured. Large errors were often found in the products submitted for 
 
test or bought in the open market. An investigation of the stand- 
 ards used by manufacturers showed that these were frequently in 
 error by amounts that could by no means be neglected. In many 
 such cases the bureau loaned or sold standards carefully verified by 
 the bureau, and the ready cooperation of the manufacturers greatly 
 facilitated the work. The steady improvement in the measuring 
 instruments submitted for test is sufficient evidence of the eflFective- 
 ness of this work. Its importance to industry itself and to the 
 general public can hardly be overestimated. Directly or indirectly 
 through the State and local inspectors and the manufacturers the 
 bureau is rapidly bringing about a realization of the need of more 
 perfect standards and providing means by which they may be applied 
 to all the varied needs of industry, science, and trade. 
 
 The bureau is, to a certain extent, a clearing house for technical 
 information. It is constantly consulted by State and municipal 
 officials, and technical bodies such as public-service corporations and 
 commissions. The bureau cooperates to the fullest extent possible 
 with all movements tending to improve conditions in which stand- 
 ards of quality or standards of measurement are involved. In this 
 way the bureau is influencing in a far-reaching way the establish- 
 ment of standardized conditions in the distribution of public services 
 as well as promoting accuracy ia commercial relations. 
 
 LENGTH. 
 
 To meet the modern demands for uniformity and precision, all 
 length standards are based upon the international meter, which is 
 defined as the distance, at the temperature of melting ice, between 
 two fine lines ruled on a bar of platinum-iridium preserved at the 
 International Bureau of Weights and Measures near Paris, France. 
 Accurate copies or prototypes have been made, and after numerous 
 comparisons with the international meter and among themselves 
 they have been distributed among the Governments of the world. 
 The bureau is in possession of national prototype No. 27. From 
 this standard are derived all other standards of length used in the 
 United States, with their subdivisions and multiples, including the 
 yard, using the relation between the yard and the meter (1 meter = 
 39.37 inches) fixed by the act of 1866. 
 
 Length measures are standardized under definite conditions of 
 temperature and manner of support. The tests include gauges, bars, 
 rules, tapes, level rods, and a great variety of special apparatus. 
 The researches in progress relate to the construction and mainte- 
 nance of standards of different types and their proper use and care. 
 Particular attention is being given to the measurement of the ex- 
 pansion of materials at high temperatures under conditions not 
 
8 
 
 covered by ordinary investigations but of prime importance in 
 modern engineering. 
 
 In most lines of construction and engineering the need of an accu- 
 rate standard of length is evident. The surveyor or engineer re- 
 quires steel tapes to measure distances and it is necessary that the 
 true length be known in terms of a universal standard of referMice. 
 The unit of length must have the same value everywhere to secure 
 perfect construction and interchangeability of parts in machinery. 
 This can only be done by having accurate and universal standards, 
 
 UASS. 
 
 To secure reliability and permanence the standard of mass (com- 
 monly called weight) is a certain cylinder of platinum-iridium 
 known as the international kilogram, also preserved at the Interna- 
 tional Bureau of Weights and Measures. From this kilogram copies 
 have been made, having the same mass, material, and form, and 
 after careful comparisons to establish their value they have been 
 distributed among the various nations of the world. The bureau is 
 in possession of two such copies, Nos. 4 and 20. From the kilogram 
 all other units of mass, such as the pound avoirdupois, pound Troy, 
 etc., are now derived in the United States. 
 
 Weights are classified according to their design and use, and are 
 tested in conformity with the classification. The weights tested 
 range from those used by a state or city sealer in testing commer- 
 cial weights and measures to those used by the scientist in most pre- 
 cise and exacting work. 
 
 Researches made from time to time cover a wide field affecting 
 directly and indirectly the maintenance, preservation, and proper 
 use of standards of mass. Millions of dollars are annually involved 
 in the tests and determinations, made by engineers and chemists, in 
 which weights of high accuracy must be used. 
 
 VOLUME. 
 
 Volume measurements, such as the gallon and bushel, are defined 
 as a certain number of cubic inches. In the metric system the 
 volume occupied by a kilogram of water at maximum density is the 
 liter. 
 
 Tests of such volumetric apparatus are made by determining the 
 amount of distilled water at a certain temperature that is contained 
 or delivered by the vessel. The tests range from half -bushel meas- 
 ures to cubic-centimeter pipettes. Each year many thousand glass 
 measuring instruments, including flasks, pipettes, burettes, cylin- 
 ders, and vessels of all kinds are tested. The test of cubic-foot 
 standards, used in standardizing gas and water meter provers, is of 
 growing importance. 
 
Investigations covering questions of detail and design are impor- 
 tant when precise volumetric measurements are involved. A con- 
 tainer made of 1-liter capacity will not deliver a full liter of a liquid, 
 and it is necessary to have precise data on this difference. Precise 
 volumetric apparatus is, therefore, marked "to contain" or "to 
 deliver." 
 
 The glassware tested is of importance to chemists. The chemist 
 in making analyses, whether of the constitution of rubber or steel or 
 of a sample of food, needs accurately calibrated glassware. With 
 the advance in modern requirements the testing of capacities is 
 steadily assuming greater importance, 
 
 DENSITY. 
 
 In a large class of materials used in commerce, science, and the 
 arts, it is important to determine the density or the weight of a 
 unit volume of a substance. In the case of liquids this can be ac- 
 complished with a high degree of accuracy by hydrometers. Hy- 
 drometers are usually glass bulbs with a stem which when placed 
 in a liquid sinks to a certain level, indicating the density by gradua- 
 tions on the stem. 
 
 In order to use hydrometers with confidence it is necessary that 
 they be carefully tested. The bureau tests annually hundreds of 
 hydrometers, largely for the use of the revenue service of the Gov- 
 ernment. Besides testing hydrometers, the bureau is called upon to 
 make careful determinations of the densities of materials, in both 
 solid and liquid forms, of special interest and importance to revenue, 
 commerce, engineering, and science. The bureau is also frequently 
 called upon to ascertain the expansion of various liquids upon in- 
 crease of temperature. 
 
 The bureau has just completed an elaborate series of investiga- 
 tions giving probably the best-known values for densities of mix- 
 tures of alcohol and water. This has a vital bearing on the work 
 of the internal-revenue branch of the Government, which collects the 
 tax on malt and spirituous liquors. 
 
 Hydrometers are used to a very great extent in the petroleum in- 
 dustry and by manufacturing chemists and in tests and classifica- 
 tions of various kinds. The importance of testing hydrometers is 
 better appreciated after knowing that the Government collects an 
 annual internal revenue of $150,000,000 on values obtained by means 
 of hydrometers. 
 
 TBASE WEIGHTS AND MEASITIIES. 
 
 The Bureau of Standards is by law charged with the preservation 
 and care of the standard weights and measures of the National Gov- 
 ernment, and soon after the establishment of the bureau, in 1901, it 
 
10 
 
 began to receive inquiries from State and private institutions, manu- 
 facturers, and from the general public for information, advice, 
 and assistance concerning weights and measures. The inquiries 
 from the beginning showed the great variation existing in the dif- 
 ferent States and the lack of standardization in many common meas- 
 ures of quantity, such as the barrel of potatoes or apples and of 
 boxes, crates, baskets of various produce, the bushel of various grains, 
 etc. Enormous losses to the public naturally result from such a con- 
 dition of affairs, and dishonest dealers take advantage of these condi- 
 tions to their own profit. 
 
 Eecognizing the benefits which would come from unifying the 
 weights and measures and methods in use throughout the country. 
 Congress made an appropriation two years ago to enable the bureau 
 to make an investigation of the actual conditions throughout the 
 States. With two inspectors engaged in this work, 170 cities in 46 
 States have been inspected. More than 8,700 scales and 18,000 pieces 
 of other weights and measures apparatus have been inspected. The 
 investigation showed that a large number of fraudulent or defective 
 weights and measures are in daily use. 
 
 Through the information thus obtained the bureau has been able 
 to point out existing evils and to aid States and cities in drafting 
 and perfecting their ordinances on this subject. The results have 
 been gratifying. During the past year 12 States have enacted laws 
 which will result in State- wide supervision and inspection of weights 
 and measures. Seventeen other States have enacted legislation of 
 a minor character — ^but nevertheless important — and 8 States con- 
 sidered legislation which failed of passage. 
 
 It is the hope of the bureau that by directing and encouraging co- 
 operation among the States uniformity will be secured, and that the 
 enormous losses now sustained by the purchasing public, whether 
 through dishonesty or carelessness, will be reduced to a minimum. 
 
 BAROMETRY. 
 
 The needs of explorers and surveyors, and the advent of the mod- 
 ern flying machine, have emphasized the need of an accurate and 
 ready means of measuring elevations. This has directed attention 
 to the limitations and imperfections of the aneroid barometer, used 
 for this purpose. The bureau is investigating the behavior of such 
 barometers of different designs under various conditions, to locate 
 the faults, with the object of improving the instrument. Standard 
 specifications and tests for these instruments are being developed 
 which as far as practicable will include all the factors affecting the 
 operation, such as mechanical accuracy, elastic lag, temperature com- 
 pensation, permanency, etc. Mercurial barometers of the ordinary 
 laboratory type and those used for meteorological purposes are also 
 tested by the bureau. 
 
11 
 
 TIME. 
 
 The bureau is preparing to take up the testing for the public of 
 the better grade of watches. They will be run for several weeks in 
 the various positions for which they are adjusted in a room heated to 
 summer temperatures and again cooled to nearly freezing. Any 
 watch passing the required tests will be granted a certificate or re- 
 port of its performance. Standards of accuracy will be established 
 which will indicate the degree of accuracy which may be expected 
 from watches of different grades and enable a purchaser to secure a 
 certified watch if he so desires. Chronometers and clocks, also, will 
 be similarly tested. The bureau recently completed an extended 
 investigation of master and secondary clocks for the Treasury De- 
 partment, to determine their suitability for installation in public 
 buildings of the Government. 
 
 EIECTRICITT. 
 
 The accurate measurement of the various electrical quantities oc- 
 curring in practice is of great commercial and technical importance, 
 as well as of scientific interest. The bureau is responsible for the 
 maintenance of the units in terms of which such measurements are 
 made, and by cooperation with other national laboratories interna^ 
 tional uniformity has been secured. In addition to this work, im- 
 proved standards and measuring apparatus have been developed, and 
 in some cases the accuracy of measurement greatly increased. The 
 testing and certification of electric instruments for all who employ 
 them in their work is also an important function of the bureau. 
 
 INTERNATIONAL ELECTRICAL UNITS. 
 
 The units to which electrical measurements are referred were 
 adopted by the London International Electrical Conference of 1908. 
 The fundamental units are the following: (1) The international ohm, 
 defined in terms of the resistance, at the temperature of melting ice, 
 of a uniform colunm of mercury of specified dimensions; and (2) 
 the international ampere, the unit of current, defined by the rate at 
 which silver is deposited by an electric current in the silver volta- 
 meter. 
 
 The completion of specifications for the voltameter, in order to 
 assure the highest accuracy and the adoption of a value for the 
 Weston normal cell used in practice to define the international volt, 
 was left to an international committee, under the auspices of which 
 cooperative work was carried out at the bureau in the spring of 
 1910 by representatives of the national laboratories of England, 
 Germany, France, and America. 
 
 The bureau has for a number of years been engaged in investiga- 
 tions having for their object the concrete realization of the funda- 
 U] js.ii J « 7i.^t---''"^ I'^^tfi ta ths hiahest degree of precision. 
 
12 
 
 ELECTBIC SESISTANCE. 
 
 Four copies of the International Ohm have been constructed. 
 This involved a study of variations in cross-section of the mercury 
 column due to minute irregularities in the capillary tube containing 
 the mercury, the accurate determination of the length of the tube, 
 its mercury content, and the precision comparisons with wire-re- 
 sistance coils employed as secondary standards for routine testing 
 work. The resistance units represented by the different tubes differ 
 from the mean of all by only 5 parts in 1,000,000, and the mean is 
 m agreement with the units employed in Germany and England to 
 a very few parts in 100,000. 
 
 ELECTRIC OTTRSENT. 
 
 The investigation of the voltameter has shown that the previously 
 recognized type was subject to large errors due to the contamination 
 of the electrolyte by the filter paper employed even when the highest 
 grade paper was used. When the latter is replaced by a porous 
 porcelain pot the results of current measurement were found to 
 agree to a few parts in 100,000, and practically the same result is 
 obtained in another type in which neither filter paper nor porous 
 pot is employed. The investigation brought to light the considerable 
 influence on the result of exceedingly small traces of certain im- 
 purities. The experience gained will be utilized in drawing up the 
 official specifications for the use of the voltameter. 
 
 ELECIROHOTIVE FORCE. 
 
 A special study has been made of the method of preparation and 
 purification of the materials employed in the construction of the 
 Weston normal cell, which is in practice used to define the unit of 
 electromotive force. The standard cell is reproducible to a few 
 parts in 100,000 if the cells are set up in accordance with specifica- 
 tions based on the result of recent investigations. 
 
 ABSOLUTE ELECTRICAL UNITS, 
 
 From the fundamental electrical units, the ohm and ampere (or 
 in practice the ohm and volt) , all the remaining units for the meas- 
 urement of electrical quantities are derivable. 
 
 There is, however, another system of electrical units based upon 
 the units of length, mass, and time, and therefore independent of the 
 properties of materials. These units are called absolute units, and 
 upon them are based the international units mentioned above. On 
 account of the scientific and theoretical importance of the subject 
 the bureau has been engaged in the development of a current balance, 
 by means of which currents can be measured with great accuracy in 
 absolute units. This involves the calculation of the precise attrac- 
 tion or repulsion of a moving coil by a pair of fixed coils, all the 
 
13 
 
 coils carrying the current to be measured. The movable coil is at- 
 tached to one arm of a balance and the force of attraction is meas- 
 ured by weighing. 
 
 The results obtained with the current balance indicate that cur- 
 rents can be measured in absolute units to within a few parts in 
 100,000 and that the absolute and international ampere do not differ 
 by more than 5 parts in 100,000. The apparatus for the determina- 
 tion of resistance in absolute measure has been constructed and the 
 measurements will shortly be carried out. 
 
 CONDTJCTIVITY, 
 
 The bureau recently made an investigation of the conductivity and 
 temperature coefficient of copper used in such enormous quantities by 
 the electrical industries. By such measurements the degree of purity 
 of a copper sample may be ascertained, certain impurities exerting an 
 influence hundreds of times greater than that corresponding to the 
 percentage in which they are present. The results obtained were 
 made the basis of the new copper wire tables adopted by the American 
 Institute of Electrical Engineers. 
 
 CAPACITY AND INDVCTANOE. 
 
 In alternating current work and in dealing with intermittent or 
 varying currents the capacity and inductance of a circuit are always 
 of importance. This applies to alternating current transmission of 
 power, to telegraphy, submarine cabling, telephony, and radioteleg- 
 raphy. Indeed, in a radiotelegraphic circuit where the changes in 
 the current are very rapid, the capacity and inductance are the most 
 important constants of the circuit. 
 
 The standards of capacity are mica and air condensers, the mica 
 condensers being used for values of the capacity greater than 0.01 
 microfarad, and the air condensers for lower values. Condensers to 
 be tested are compared with these standards by the use either of al- 
 ternating or direct current, according to the purpose for which the 
 condensers are to be used. Frequencies of alternating current from 
 25 to 3,000 cycles are available for this use. 
 
 The standards of inductance are coils of copper wire wound on 
 marble spools, which are nonmagnetic and very permanent. Stand- 
 ards are also in the possession of the bureau, which are so wound that 
 their inductance can be computed from their dimensions. 
 
 ELEOTEIO INSTEUMENTS. 
 
 Another branch of electrical work is the testing of the electric 
 measuring instruments largely used by electrical engineers. This 
 occupies a mid-position between the work of an engineering labora- 
 tory and that of a scientific one. An important part of the work 
 is the thorough investigation of instrument types. 
 
14 
 
 Among the instruments tested and certified by the bureau are 
 resistance standards, precision rheostats, wheatstone bridges, poten- 
 tiometers and other resistance apparatus, and standard cells, all of 
 which are employed in scientific work and in the more accurate meas- 
 urement of the testing laboratories of the manufacturers of electrical 
 apparatus, and of the light and power companies. 
 
 The instruments most frequently tested are ammeters, voltmeters, 
 wattmeters, watt-hour meters, and current and potential transformers, 
 although many other types are often tested. The reference standards 
 most used in this work are standard cells and standard resistances, and 
 the potentiometer, which is the most accurate device for the measure- 
 ment of voltage. A small testing room has been installed, the tem- 
 perature of which may be maintained at any desired value between 
 considerable limits, so that the effect of temperature upon any in- 
 strument may be determined. 
 
 The watt-hour meter is the instrument of the greatest direct com- 
 mercial importance since it is almost universally used wherever elec- 
 tric power is sold. Instrimient transformers are used as auxiliary 
 apparatus in the measurement of very large amounts of power in 
 alternating-current circuits. 
 
 The accuracy required in all such measurements is steadily increas- 
 ing, and consequently instruments are being developed to increase 
 both the range and the accuracy of such measurements. 
 
 MAGNETISU. 
 
 Because of its magnetic properties iron enters to a great extent 
 into the construction of electrical machinery and apparatus. Its 
 value consists largely in its intense magnetization when it is sub- 
 jected to moderate magnetizing forces. This property of having a 
 high magnetic permeability makes it useful for field magnets and 
 armatures in a great variety of machines and apparatus and for 
 alternating-current transformers. A second characteristic is the 
 retention of a certain amount of magnetization after the magnetizing 
 force has been removed. This property is valuable in steel to be 
 used for permanent magnets, such as are used in telephone receivers, 
 magnetos, and electric measuring instruments. 
 
 The measurements of the above characteristics are made with 
 direct current, and are known as normal-induction and hysteresis 
 measurements. 
 
 Besides the above there is another characteristic of iron and steel 
 which is of great importance for material to be used in armatures, 
 transformers, and all devices in which there is a repeated reversal 
 of magnetization. This is the energy loss that inevitably results 
 when iron or steel has its magnetization reversed, and is known as 
 
15 
 
 core loss. It is very desirable that this loss be kept as low as possible. 
 It has been estimated that in the United States alone the energy 
 dissipated in core losses amounts to millions of dollars annually. 
 Recently great improvements in material have been made, and the 
 best transformer steels of to-day show only half the loss of the best 
 material of a decade ago. 
 
 Investigations are in progress to show the relation between the 
 magnetic properties and the chemical composition and heat treat- 
 ment of various steels. 
 
 Other materials besides iron and iron alloys are of importance 
 from a magnetic standpoint. For certain purposes it is desirable 
 to have as nearly nonmagnetic materials as possible. Some alloys 
 containing a considerable percentage of iron are practically non- 
 magnetic, while certain alloys of nonmagnetic metals are magnetic. 
 An investigation of such slightly magnetic materials is, therefore, 
 sometimes of importance. 
 
 PHOTOMETET. 
 
 The photometric work of the bureau includes, besides research 
 work in various lines, (1) maintaining the unit of candlepower 
 which, at the proposal of the bureau, was accepted by the national 
 laboratories of England and France, and is preserved through the 
 mediimi of incandescent electric lamps; (2) the preparation and 
 testing of electric lamps to be used as photometric standards; (3) 
 the verification of gas lamps used as standards in the photometric 
 measurements of gas; (4) the inspection and life testing of incan- 
 descent electric lamps purchased by the Government departments. 
 
 The adoption of the new candlepower unit of the bureau by both 
 the gas and electrical industries has brought about uniformity in 
 the photometric standards throughout the country. 
 
 Standard specifications for incandescent lamps issued by the 
 bureau are recognized by all manufacturers and have brought 
 about a uniformity in the rating of lamps which is very much to 
 the advantage of both makers and users. These specifications are 
 frequently revised after conference between representatives of the 
 Government and of the manufacturers. 
 
 Investigations are now in progress to determine the constancy of 
 incandescent electric lamps, the accuracy of photometric measure- 
 ments, and the reliability of flame standards employed in the pho- 
 tometry of illizminating gas. 
 
 ELECTROIYSIS. 
 
 Since the advent of trolley systems a great amount of damage to 
 gas and water pipes and other subsurface structures has been ex- 
 perienced, due to the presence of stray currents in the earth. Vast 
 
16 
 
 siuns are spent every year by gas, water, and railway companies and 
 by municipalities in efforts to mitigate this evil. While a great 
 deal of progress has been made in methods of minimizing trouble 
 from this source, much remains to be done before remedial measures 
 can be applied with the degree of certainty which modern engineer- 
 ing practice demands. Closely associated with electrolysis from 
 stray currents is the phenomenon of autoelectrolysis or self-corrosion, 
 due to the presence in the soil of foreign substances, such as coal, 
 coke, cinders, etc., which give a difference of potential against iron, 
 or to differences in the physical structure of the iron itself. Corro- 
 sion due to this cause is often difficult if not impossible to distinguish 
 clearly from that due to stray currents. 
 
 During the last few years much attention has been called to the 
 possibility of damage to reenforced concrete by stray currents, and 
 considerable alarm has been aroused in some quarters lest reinforced 
 concrete buildings, bridges, and similar structures be seriously in- 
 jured in this way. Whether or not such grave danger actually exists, 
 the possibility of such danger having been established, the problem 
 becomes one of extreme importance, and a thorough study of the con- 
 ditions under which the trouble may occur, as well as the best 
 methods of preventing or minimizing the trouble, is imperative. 
 Eecognizing the importance of the subject, and acting in response to 
 important engineering interests,- the Bureau of Standards is engaged 
 in a comprehensive investigation of this subject, involving all the 
 different phases of the problem. This work has been in progress for 
 more than a year past, and several papers representing the results 
 of the work to date are now in preparation. It is planned to con- 
 tinue this work as circumstances may require. 
 
 HEAT AND THERMOMETRY. 
 
 The work of the bureau in connection with heat measurements is 
 primarily the maintenance of a standard scale of temperature always 
 available to the public for reference, and, secondarily, the making 
 of tests and the investigation of problems of all sorts in which ac- 
 curacy in the measurements of temperatures is essential or which 
 for other reasons may advantageously be conducted in laboratories 
 especially equipped for experimental work in heat. 
 
 The standard scale of temperature between 0° and 100° C. (32° 
 and 212° F.) is represented by a series of standard mercurial ther- 
 mometers, which agree to within 0?002 C. with those which define 
 the scale of the International Bureau of Weights and Measures. 
 Above and below this range the scale is founded on a number of fixed 
 base points reproducible by the boiling or freezing points of chem- 
 ically pure substances. The value of these base points are expressed 
 
17 
 
 in terms of the gas scale. Measurements of temperature are made 
 by thermometers or pyrometers of various types standardized at 
 these base points; and any thermometer or pyrometer sent in for 
 test is standardized in terms of the scale of the bureau, by com- 
 parison with such instruments, or by test at the base points. Among 
 the instruments so tested the following classes are of obvious im- 
 portance: Clinical thermometers, of which some 15,000 are tested 
 every year; calorimetric thermometers, used in determining fuel 
 values, especially in connection with the award and settlement of 
 coal contracts ; mercurial thermometers, for use in controlling various 
 technical operations conducted below red heat; pyrometers of many 
 kinds — resistance, thermoelectric, optical, total radiation, etc. — which 
 are used in a great variety of technical operations, e. g., in the glass, 
 ceramic, and metallurgical industries, where high temperatures must 
 be accurately controlled. 
 
 An important branch of work directly dependent on the possession 
 of very exact means for measuring temperatures is that of determin- 
 ing the specific heats and heats of combustion of substances. This 
 includes the heats of combustion of certain pure gases which enter 
 into the composition of illuminating gas and certain materials capa- 
 ble of a high degree of purification, such as sucrose, naphthalene, 
 and benzoic acid, which are distributed to outside fuel-testing labora- 
 tories for use in standardizing their own instruments. 
 
 The variety of miscellaneous tests on the thermal properties of 
 materials requested from the bureau is very large, among the most 
 important being tests of the melting points of fire brick and other 
 refractory substances, and of the melting or transition points of al- 
 loys, in connection with which an elaborate investigation of the effect 
 of heat treatment on the modern steels is under way. 
 
 Besides the work already noted, which has a direct connection with 
 the improved conduct of technical operations in the great industries, 
 various researches are in progress tending to the improvement of 
 methods of precise measurement in the domain of heat or of our 
 knowledge of important thermal constants. Among these investi- 
 gations may be mentioned: Studies of freezing and boiling points 
 for the further fixation of the standard scale of temperature; the 
 development of accurate methods of calorimetry; the investigation, 
 at high temperatures, of the laws of radiation on which the indica- 
 tions of optical and other radiation pyrometers depend, and of the 
 emissive powers of various materials at which such pyrometers may 
 be sighted ; an investigation of some properties of the thermometric 
 gases at ordinary and low temperatures; a comparison of various 
 instruments for testing the viscosity of lubricating oils, etc. 
 
18 
 
 OPTICS. 
 
 The work in optics consists chiefly in the determination of the 
 optical properties of materials and optical constants, which includes 
 radiometry, spectrometry, polarimetry, and interferometry. Such 
 researches are valuable in supplementing other methods used for 
 this purpose. Besides the researches mentioned, many optical tests 
 are made for the Government and the general public, such as tele- 
 scopic and photographic lenses, prisms, samples of glass, polariscopic 
 apparatus, and sugar analyses. 
 
 In interferometry researches have been completed or are in prog- 
 ress on the use of spectrum lines and their application to the most 
 refined methods of measurement of length. 
 
 The bureau has determined the purity and intensity of many 
 sources of monochromatic light, the relation between the luminous 
 intensity and energy intensity of radiation, the radiation of conduct- 
 ing helium gas as a primary light standard, the fidelity of photo- 
 graphic lenses as to reproduction, the luminous equivalent of radia- 
 tion, and many other problems of a similar nature. An important 
 investigation recently published relates to the luminous equivalent 
 of radiation, a problem which underlies the theory of light measure- 
 ment and the establishment of a rational absolute scale of luminous 
 intensity. A method has also been developed for constructing a 
 rational color scale and establishing primary standards of pure color. 
 This is an important subject and one which has many industrial and 
 technical applications. 
 
 The bureau in its radiometric work investigates various problems 
 in light and heat emission, absorption, and reflection, particularly 
 in the infra-red. It has studied the laws of radiation of various sub- 
 stances and also the instruments and methods used in such researches. 
 An exact determination of the spectral reflecting power of metals 
 has also been published. 
 
 Raw sugars that are imported are also tested to determine their 
 purity, which it is necessary to know in order to fix the amount 
 of the tariff duty. In this connection samples are sent in daily from 
 the various customhouses for test. Exhaustive researches are also 
 carried on to improve the methods and instruments used for test- 
 ing at the ports of entry. The importance of applying the most ac- 
 curate and scientific methods of polarimetry to the collection of the 
 revenue on sugar and to industrial processes is increasing. For 
 this purpose, among other things, pure sugar is indispensable. The 
 problem of producing relatively large quantities of this material 
 of unexcelled purity has been successfully solved by recrystalliza- 
 tion in a vacuum. The demand on the bureau for samples of this 
 sugar is rapidly growing, and many samples are now sent out for 
 
19 
 
 scientific use. The distribution of such samples for standardization 
 marks an important step in optical measurements and calorimetry. 
 
 CHEMISTRY. 
 
 Broadly spealdng, the chemical work of the Bureau of Standards 
 is of two kinds, routine and research, done independently or in co- 
 operation with the various divisions of the bureau. By far the 
 larger part of the routine work is on behalf of the Government — 
 analyses of iron, steel, alloys, cement, rubber, oils, paints, varnishes, 
 papers, inks, and similar miscellaneous materials. Most of this 
 work is done for the Isthmian Canal Commission, the Office of the 
 Supervising Architect of the Treasury, the Government Printing 
 Office, and the General Supply Committee of the Government de- 
 partments at Washington. As examples of research work on behalf 
 of the Government may be mentioned investigations upon cellu- 
 loid and articles made from it, with reference to their acceptance 
 for transportation in passenger vessels of the United States; print- 
 ing and record inks, with a view to improving their quality; the 
 celluloses used in paper, the effect of age, sizing, etc., upon them; 
 the preparation of the purest possible ethyl alcohol to serve as a 
 basis for new density tables for mixtures of alcohol and water for 
 use by the Internal Eevenue and Customs Services. 
 
 TESTING MATESIALS. 
 
 An important branch of the bureau's work relates to the testing 
 of materials. This was part of the work assigned to the bureau 
 by act of Congress, March 3, 1901, by which the bureau was estab- 
 lished. The development of the work was taken up as rapidly as 
 funds were provided for it until it now includes a large variety of 
 structural, engineering, and miscellaneous materials. The impor- 
 tance of official tests of materials by the Bureau of Standards arises 
 from the fact that the bureau has the facilities for all kinds of phys- 
 ical measurements. Among the more important materials may be 
 mentioned cements, concretes, steels, irons, bricks, clays, nonferrous 
 metals, alloys, and rubbers for various purposes, leathers, papers, 
 cloths, inks, paints, mucilages, twines, ropes, oils, and many others. 
 In many cases satisfactory methods of test are not available, and 
 researches are necessary to devise new methods. The routine tests 
 of such materials are more or less directly concerned with every de- 
 partment and bureau in the Government service as well as the gen- 
 eral public. Equally important with the testing is the study of 
 the practical and scientific basis for specifications, the desirable 
 qualities in materials, their accurate description in terms of phys- 
 ical and chemical properties which may be measured or tested by 
 standard tests and analyses, standard methods of sampling, stand- 
 
20 
 
 ard instruments and methods of testing, and finally the preparation 
 of standard specifications for the guidance of the manufacturer and 
 purchaser. This work should eventually result in the adoption of 
 definite specifications and tests for all materials in use and thus 
 furnish a scientific basis for manufacture and sale and a reliable 
 and impersonal standard for inspection and acceptance. 
 
 CEMENT. 
 
 In connection with the testing of structural materials, the bureau 
 is conducting several cement-testing laboratories in Washington, 
 Pittsburgh, and elsewhere, where the cement used in the construc- 
 tion of public buildings in all parts of the United States is tested. 
 The cement used in the construction of the Panama Canal is tested 
 by the bureau in its branch laboratory at Northampton, Pa. The 
 quantity inspected at this laboratory averages from 5,000 to 7,500 
 barrels per day. 
 
 In addition to the routine testing of cement various problems are 
 being investigated, and studies are being made in an endeavor to 
 improve the methods of testing. A small cement kUn has been 
 installed at Pittsburgh for studying problems in connection with 
 the manufacture of cement, varying the character of the raw ma- 
 terials used, temperature of burning, etc., and studying the effects 
 of these variations in connection with physical tests. An exposure 
 station has recently been established at Charleston, S. C, for con- 
 tinuing the investigation, started at Atlantic City, as to the effect 
 of sea water on cements, mortars, and concretes. A number of 
 technical papers giving the results of important investigations upon 
 cement and concrete are now in press. The preparation of standard 
 specifications for cement is now in progress under the auspices of 
 the Bureau of Standards, to fix uniform tests and requirements for 
 the United States. 
 
 PAPEB. 
 
 bf vital importance to all users of paper is the bureau's investi- 
 gation and testing of papers. As in other lines, testing and research 
 are proceeding together. The bureau tests all the papers used in the 
 publications and printing of the National Government. Experts 
 now furnish the data necessary to eliminate undesirable papers, and 
 quality is determined by scientific tests rather than by inspectors' 
 judgment. As a result of the movement for more intelligent buying, 
 print papers are bought on specifications and samples of all deliv- 
 eries are analyzed and tested at the bureau. The bureau determines 
 the fiber composition by the microscope, the folding endurance by 
 ,the Schopper folder, the weight by special balances, the bursting 
 strength on standard paper testers carefully calibrated in advance, 
 
21 
 
 and the tensile strength and thickness by special devices. After 
 several years of such work the ground is prepared for a thorough 
 examination into the factors which affect the qualities of paper. 
 The analyses of the bureau are such as to enable the expert to repro- 
 duce the formula by which the paper was made. The researches in 
 progress include the effects of humidity upon the properties of paper, 
 such as strength, weight, thickness; the deterioration of paper by 
 coloring matter, loading, sizing, etc., and the study of the dura- 
 bility of wood cellulose as compared with cotton and linen. The 
 bureau has installed a paper-making machine for producing experi- 
 mental papers under predetermined conditions and of definite compo- 
 sition. This will enable the bureau to investigate the properties of 
 paper by the rigorous control of the conditions of its production. 
 
 TEXTILES. 
 
 The bureau is engaged in the determination of the physical prop- 
 erties of textile materials from the raw fiber to the finished product. 
 These tests include a wide range of measurement, such as the deter- 
 mination of the absorption of moisture by wool, cotton, silk, and jute 
 fiber at different percentages of relative humidity ; the shrinkages of 
 raw wool ; the temperatures to be applied to the different fibers to ob- 
 tain constant or bone-dry weight; the textile strength of yarn and 
 other fabric as affected by using different lengths of test pieces ; the 
 effect of moisture upon the length, strength, weight, durability, 
 etc., of textiles. Textile raw materials are sold by weight, and the 
 change of weight due to the absorption from the air is therefore a 
 matter of commercial importance. Other vital problems in connec- 
 tion with textiles are in progress, in which the Government depart- 
 ments, the manufacturers, and dealers have expressed a keen interest. 
 
 MISCELLANEOTTS IIATEKIAI.S. 
 
 Among the materials tested are cast iron, steel, and other metals, 
 leather, mechanical rubber goods, asbestos sheet packing and other 
 general supplies. The metals are tested for strength and to deter- 
 mine compliance with specifications, which vary according to the 
 intended use of the material. Finished metal products, such as tools, 
 saw blades, etc., are tested under working conditions, the tests vary- 
 ing with the uses, frequently involving special investigations. 
 
 Leather is inspected for quality and tested for strength, stretch, 
 absorption, and weight, to determine its adaptability for special 
 usage, such as belting, belt lacing, harness, shoes, and other products. 
 Rubber, in the form of mechanical rubber goods, such as sheet pack- 
 ing, valves, water hose, air hose, steam hose, suction hose, dredging 
 sleeves, rubber belting, etc., is tested for strength, elasticity, and gen- 
 
22 
 
 » 
 
 eral quality, as indicated by its behavior under working conditions, 
 as well as certain special tests which have been developed for such 
 materials. 
 
 Much of this work has been done for the Isthmian Canal Commis- 
 sion and the various Government departments, with the result that 
 after a number of rejections on account of failure to comply with 
 specifications it is now found that such materials purchased on con- 
 tract are of much better and more uniform quality than it was pos- 
 sible to obtain before the custom of testing had been introduced. The 
 saving in expense is at the same time appreciable. 
 
 Special investigations are now being carried on to determine the 
 physical properties of various rubber compounds which are used in 
 the manufacture of mechanical rubber goods, with a view to develop- 
 ing standard specifications for such materials as hose, packing, etc. 
 Similar work is being done in the case of leather belting. 
 
 ENGINEERING INSTRUMENTS. 
 
 A large class of measuring instruments are used in the various 
 branches of engineering. The investigation and testing of such 
 instruments is an important part of the bureau's work, comprising, 
 among others, water-current meters, anemometers, speedometers, 
 taximeters, tachometers, pressure gauges, water meters, gas meters, 
 steam-engine indicators. These instruments are tested for accuracy, 
 and certificates issued showing corrections where desired. 
 
 ENGINEERING TESTING. 
 
 The work of testing materials requires a large variety of testing 
 instruments and other equipment. Among these may be mentioned 
 the 2,300,000-pound Emery testing machine for load of tension and 
 compression to accommodate specimens up to 30 feet in length. At 
 its Pittsburgh laboratory the bureau is erecting a 10,000,000-pound 
 Olsen testing machine. A number of other machines of smaller 
 capacity are available for lower ranges. As an example of research 
 with such testing machines may be mentioned the investigation in 
 conjunction with the American Society of Civil Engineers of the 
 strength of a series of steel columns which will be tested to correct 
 and confirm the formulas used by engineers for computing column 
 strength — formulas upon which the efficiency and safety of building 
 construction depend. 
 
 The bureau is engaged in the test of structures in which strain 
 measurements are taken of deformation under dead loads. This 
 class of work includes civil engineering and architectural structures, 
 embracing bridges, buildings, railway tracks, steam boilers, and 
 pavements. Strain measurements are carried on in conjunction with 
 
23 
 
 laboratory tests of the physical properties of the different materials 
 represented in engineering structures. This embraces close observa- 
 tions on the behavior of the materials in service, supplementary to 
 but beyond the scope of testing machinery. The value of this work 
 lies in the fact that it is directly applicable to service conditions and 
 is made upon material as actually used in finished structures and 
 subject to working conditions. 
 
 This work is the summation of all testing, inasmuch as it embraces 
 all the factors present in materials in structures. The work has in- 
 cluded measurement during construction on some of the tallest build- 
 ings in New York City. 
 
 PTJBIICATIONS. 
 
 An important function of the bureau is the distribution of informa- 
 tion. This is done through personal visits of the people who desire 
 special information, such as manufacturers, technical experts, and 
 others who wish to consult the scientific officers of the bureau regard- 
 ing their work and to inspect the bureau's plant and equipment. 
 Such information is also largely accomplished by means of corre- 
 spondence, which is steadily increasing in volume. Finally the most 
 important medium of distribution of information concerning the 
 bureau and its work is through its publications. The Bulletin of 
 the Bureau of Standards embodies the results of the scientific work 
 of the bureau in reference to standards, instruments, methods of 
 measurement, and physical constants. The bulletin contains the col- 
 lected papers, of which about one volume is issued each year. The 
 Circular of the Bureau of Standards contains information upon 
 scientific subjects, including methods of testing, the properties of 
 materials, legislation concerning weights and measures, regulations, 
 specifications, and other information of general interest. The Tech- 
 nologic Papers of the Bureau of Standards cover the more strictly 
 technologic work of the bureau. The separate scientific papers are 
 issued in the form of reprints for general distribution upon request. 
 In addition to the above, the bureau also issues miscellaneous publi- 
 cations, including the descriptive pamphlet of the metric system, 
 tables of equivalents, reports of weights and measures conferences, 
 and similar material. 
 
 EftriPMENT. 
 
 Besides an extensive modern equipment of scientific instruments 
 and apparatus for experimental and testing work, the general equip- 
 ment of the bureau is in many respects unique, since the range of 
 scientific work embraces so wide a variety of needs. In temperature 
 work ranges must be available from, that of liquid air to the heat of 
 the electric arc; in electrical work all varieties and the maximum 
 ranges of current practicable are used; in chemical work the usual 
 
24 
 
 facilities are supplemented by many special services. For all divi- 
 sions of the work are available, as required, electrical power, refrig- 
 eration, steam, gas, compressed air, vacuum, hot, cold, iced, and 
 distilled water, liquid air, cold brine, etc. In certain classes of work 
 temperature control is required. In others control of the humidity 
 is needed, e. g., the water is frozen from the air reducing the humidity 
 to the desired point, while in others the humidity is varied at will. 
 Similarly other conditions are controlled to secure the best conditions 
 for effective work. 
 
 The bureau has a technical library of more than 8,000 bound 
 volumes — chiefly on physics, chemistry, and -technologj' — and regu- 
 larly receives 270 journals and proceedings of scientific and technical 
 societies. Access to the literature in any subject is desirable for 
 effective work, especially in technical investigations. 
 
 The character and quantity of the results attained by the bureau 
 have largely depended upon the facilities available for constructing 
 special apparatus for its investigation and testing. In almost every 
 field new and improved apparatus must be designed and constructed. 
 The bureau is therefore provided with a well-equipped instrument 
 shop, skilled mechanicians, and modern machinery, which have been 
 an important factor in the maintenance of a high standard in its 
 technical work. 
 
 O 
 
Cornell University Library