FIFTY YEARS OF SCIENCE

55

FIFTY YEARS OF SCIENCE
BEING THE ADDRESS DELIVERED AT YORK
TO THE BRITISH ASSOCIATION
AUGUST 1881

BY THE EIGHT HON.

SIB JOHN LUBBOCK, BT., M.P., F.R.S., D.C.L., LL.D.
PRESIDENT OF THE ASSOCIATION ; PRINCIPAL OF THE LONDON WORKING
MEN'S COLLEGE; PRESIDENT OF THE LONDON CHAMBER OF COMMERCE;
AND VICE-CHAIRMAN OF THE LONDON COUNTY COUNCIL.

FOURTH

EDITION

London
MACMILLAN

AND

CO.

AND NEW YORK

1890
The Right of Translation and Reproduction is Reserved

RICHARD CLAY AND SONS, LIMITED,
LONDON AND BUNGAY

First Edition (8vo.), January 1882
Reprinted February and May 1882
New Edition (Crown 8vo.) 1890

ADDBESS
TO THE

BEITISH ASSOCIATION, 1881.
I N the name of the British Association, which for
the time I very unworthily represent, I beg to tender
to you, my Lord Mayor, and through you to the City
of York, our cordial thanks for your hospitable invitation and hearty welcome.
We feel, indeed, that in coming to York we are
coming home. Gratefully as we acknowledge and
much as we appreciate the kindness we have experienced elsewhere, and the friendly relations which
exist between this Association and most—I might
even say, all—our great cities, yet Sir R. Murchison
truly observed at the close of our first meeting in
1831, that to York, c as the cradle of the Association,
we shall ever look back with gratitude ; and whether
we meet hereafter on the banks of the Isis, the Cam,
or the Forth, to this spot we shall still fondly revert/

6

ADDRESS TO BRITISH ASSOCIATION, 1881.

Indeed, it would have been a matter of much regret
to all of us, if we had not been able on this, our
fiftieth anniversary, to hold our meeting in this—
our mother city.
My Lord Mayor, before going further, I must express my regret, especially when I call to mind the
illustrious men who have preceded me in this chair,
that it has not fallen to one of my eminent friends
around me, to preside on this auspicious occasion.
Conscious, however, as I am of my own deficiencies,
I feel that I must not waste time in dwelling on
them, more especially as in doing so I should but
give them greater prominence. I will, therefore,
only make one appeal to your kind indulgence. .
The connection of the British Association with the
City of York does not depend merely on the fact that
our first meeting was held here. It originated in a
letter addressed by Sir D. Brewster to Professor
Phillips, as Secretary to your York Philosophical
Society, by which the idea was warmly taken up.
The first meeting was held on September 26, 1831,
the chair being occupied by Lord Milton, who delivered an address,, after which Mr. William Vernon
Harcourt, Chairman of the Committee of Management, submitted to the meeting a code of rules which
had been so maturely considered, and so wisely framed,
that they have remained substantially the same down
to the present day.

THE PROGRESS OF SCIENCE.

'

7

Of those who organised and took part in that first
meeting, few, alas! remain. Brewster and Phillips,
Harcourt and Lord Milton, Lyell and Murchison, all
have passed away, though their memories live among
us. Some few, indeed, of those present at our first
meeting, we rejoice to see here to-day, including one
of the five members constituting the original organising Committee, our venerable Vice-President,
Archdeacon Creyke.
^The constitution and objects of the Association
were so ably described by Mr. Spottiswoode, at Dublin,
and are so well known to you, that I will not dwell
on them this evening. The President of the Eoyal
Society, in the same address, suggested that the past
history of the Association would form an appropriate
theme for the present meeting. The history of the
Association, however, is really the history of science,
and I long shrank from the attempt to give even a
panoramic survey of a subject so vast and so difficult;
nor should I have ventured to make any such attempt,
but that I knew I could rely on the assistance of
friends in every department of science.
Certainly, however, this is an opportunity on which
it may be well for us to consider what have been
the principal scientific results of the last half-century,
dwelling especially on those with which this Association is more directly concerned, either as being the
work of our own members, or as having been made

8

ADDRESS TO BRITISH ASSOCIATION, 1881.

known at our meetings. I have, moreover, especially
taken those discoveries which the Royal Society has
deemed worthy of a medal. It is of course impossible within the limits of a single address to do more
than allude to a few of these, and that very briefly.
In dealing with so large a subject I first hoped that
I might take our annual volumes as a text-book.
This, however, I at once found to be quite impossible.
For instance, the first volume commences with a
Report on Astronomy, by Sir G. Airy; I may be
pardoned, I trust, for expressing my pleasure at finding that the second was one by my father, on the
Tides, prepared like the preceding at the request of
the Council; then comes one on Meteorology by
Forbes ; Radiant Heat, by Baden Powell; Optics, by
Brewster; Mineralogy, by Whewell, and so on. My
best course will therefore be to take our different
Sections one by one, and endeavour to bring before
you a few of the principal results which have been
obtained in each department.
The Biological Section is that with which I have
been most intimately associated, and with which it is,
perhaps, natural that I should begin.
Fifty years ago it was the general opinion that
animals and plants came into existence just as we
now see them. We took pleasure in their beauty;
their adaptation to their habits and mode of life in

BIOLOGY—THE DARWINIAN THEORY.

9

many cases could not be overlooked or misunderstood.
Nevertheless, the book of Nature was like some
missal richly illuminated, but written in an unknown
tongue. The graceful forms of the letters, the
beauty of the colouring, excited our wonder and
admiration; but of the true meaning little was known
to u s ; indeed we scarcely realised that there was any
meaning to decipher. Now glimpses of the truth are
gradually revealing themselves ; we perceive that there
is a reason—and in many cases we know what that
reason is—for every difference in form, in size, and in
colour; for every bone and every feather, almost for
every hair. Moreover, each problem which is solved
opens out vistas, as it were, of others perhaps even
more interesting. With this important change the
name of our illustrious countryman, Darwin, is intimately associated, and the year 1859 will always be
memorable in science as having produced his work
on ' The Origin of Species/ In the previous year he
and Wallace had published short papers, in which
they clearly state the theory of natural selection, at
which they had simultaneously and independently
arrived. We cannot wonder that Darwin's views
should have at first excited great opposition. Nevertheless from the first they met with powerful support,
especially in this country, from Hooker, Huxley, and
Herbert Spencer. The theory is based on four
axioms:—

10

ADDKESS TO BE1TISH ASSOCIATION, 1881.

' 1. That no two animals or plants in nature are
identical in all respects.
' 2. That the offspring tend to inherit the peculiarities of their parents.
' 3. That of those which come into existence, only
a small number reach maturity.
' 4. That those which are, on the whole, best
adapted to the circumstances in which they are
placed, are most likely to leave descendants/
Darwin commenced his work by discussing the
causes and extent of variability in animals, and the
origin of domestic varieties; he showed the impossibility of distinguishing between varieties and species,
and pointed out the wide differences which man has
produced in some cases—as, for instance, in our
domestic pigeons, all unquestionably descended from
a common stock. He dwelt on the struggle for existence (since become a household word), which,
inevitably resulting in the survival of the fittest,
tends gradually to adapt any race of animals to
the conditions in which it occurs.
While thus, however, showing the great importance
of natural selection, he attributed to it no exclusive
influence, but fully admitted that other causes—
the use and disuse of organs, sexual selection, &c.
—had to be taken into consideration. Passing on to
the difficulties of his theory, he accounted for the
absence of intermediate varieties between species

BIOLOGY—LINKS BETWEEN SPECIES.

11

to a great extent, by the imperfection of the geological
record. Here, however, T must observe that, as I
have elsewhere remarked, those who rely on the
absence of links between different species really argue
in a vicious circle, because wherever such links do
exist they regard the whole chain as a single species.
The dog and jackal, for instance, are now regarded as
two species, but if a series of links were discovered
between them they would be united into one. Hence
in this sense there never can be links between any
two species, because as soon as the links are discovered the species are united. Every variable species
consists, in fact, of a number of closely connected links.
But if the geological record be imperfect, it is
still very instructive. The further palaeontology has
progressed, the more it has tended to fill up the gaps
between existing groups and species: while the
careful study of living forms has brought into prominence the variations dependent on food, climate,
habitat, and other conditions, and shown that many
species long supposed to be absolutely distinct are so
closely linked together by intermediate forms that it
is difficult to draw a satisfactory line between them.
Thus the European and American bisons are connected by the Bison priscus of Prehistoric Europe;
the grizzly bear and the brown bear, as Busk has
shown, are apparently the modern representatives of
the cave bear; Flower has pointed out the

12

ADDRESS TO BRITISH ASSOCIATION, 1881.

palseontological evidence of gradual modification of
animal forms in the Artiodactyles; and we may
say, as a general rule, that the earliest known
mammalia belong to less specialised types than our
existing species. They are not well-marked Carnivores, Rodents, Marsupials, &c, but rather constitute
a group of generalised forms from which our present
well-marked orders appear to have diverged. Among
the Invertebrata, Carpenter and Williamson have
proved that it is almost impossible to divide the
Foraminifera into well-marked species; and, lastly,
among plants, there are large genera, as, for instance,
Rubus and Hieracium, with reference to the species
of which no two botanists are agreed*
The principles of classification point also in the
same direction, and are based more and more on the
theory of descent. Biologists endeavour to arrange
animals on what is called the f natural system/ No
one now places whales among fish, bats among birds,
or shrews with mice, notwithstanding their external
similarity; and Darwin maintained that < community
of descent was the hidden bond which naturalists
had been unconsciously seeking/ How else, indeed,
can we explain the fact that the framework of bones
is so similar in the arm of a man, the wing of a bat,
the fore-leg of a horse, and the fin of a porpoise—
that; the neck of a giraffe and that of an elephant
contain the same number of vertebrae ?

THE PRINCIPLES OF CLASSIFICATION.

13

Strong evidence is, moreover, afforded by embryology ; by the presence of rudimentary organs and
transient characters, as, for instance, the existence in
the calf of certain teeth which never cut the gums,
the shrivelled and useless wings of some beetles, the
presence of a series of arteries in the embryos of the
higher Vertebrata exactly similar to those which supply the gills in fishes, even the spots on the young
blackbird, the stripes on the lion's cub; these, and innumerable other facts of the same character, appear
to be incompatible with the idea that each species
was specially and independently created; and to
prove, on the contrary, that the embryonic stages
of species show us more or less clearly the structure
of their ancestors.
Darwin's views, however, are still much misunderstood. I believe there are thousands who consider
that according to his theory a sheep might turn into
a cow, or a zebra into a horse. No one would more
confidently withstand any such hypothesis, his view
being, of course, not that the one could be changed
into the other, but that both are descended from a
common ancestor.
No one, at any rate, will question the immense
impulse which Darwin has given to the study of
natural history, the number of new views he has
opened up, and the additional interest which he has
aroused in, and contributed to, Biology. When we

14

ADDRESS TO BRITISH ASSOCIATION, 1881.

were young we knew that the leopard had spots, the
tiger was striped, and the lion tawny; but why this
was so it did not occur to us to ask ; and if we had
asked no one could have answered. Now we see at
a glance that the stripes of the tiger have reference
to its life among jungle-grasses; the lion is sandy like
the desert; while the markings of the leopard resemble spots of sunshine glancing through the leaves.
Again, Wallace in his charming essays on natural
selection has shown how the same philosophy may be
applied even to birds' nests—how, for instance,
open nests have led to the dull colour of hen birds;
the only British exception being the kingfisher, which
as we know, nests in river-banks. Lower still,
among insects, Weismann has taught us that
even the markings of caterpillars are full of interesting lessons; while, in other cases, specially among
butterflies, Bates has made known to us the curious
phenomena of mimicry.
The science of embryology may almost be said to
have been created in the last half-century. Fifty
years ago it was a very general opinion that animals
which are unlike when mature, were dissimilar from
the beginning. It is to Von Baer, the discoverer of
the mammalian ovum, that we owe the great
generalisation that the development of the egg is in
the main a progress from the general to the special,
that zoological affinity is the expression of similarity

EMBEYOLOGY—THE KEY TO DEVELOPMENT. 1
5
of development, and that the different great types of
animal structure are the result of different modes of
development—in fact, that embryology is the key to
the laws of animal development.
Thus the young of existing species resemble in
many cases the mature forms which flourished in
ancient times. Huxley has traced up the. genealogy
of the horse to the Miocene Anchitherium, and his
views have since been remarkably confirmed by
Marsh's discovery of the Pliohippus, Protohippus,
Miohippus, and Mesohippus, leading down from the
Eohippus of the early tertiary strata. In the same
way Boyd-Dawkins and Gaudry have called attention to the fact that just as the individual stag
gradually acquires more and more complex antlers:
having at first only a single prong, in the next year
two points, in the following three, and so on; so the
genus, as a whole, in Middle Miocene times, had two
pronged horns; in the Upper Miocene, three; and
that it is not till the Upper Pliocene that we find
any species with the magnificent antlers of our
modern deer. I t seems to be now generally admitted
that birds have come down to us through the
Dinosaurians, and, as Huxley has shown, the profound break once supposed to exist between birds
and reptiles has been bridged over by the discovery of
reptilian birds and bird-like reptiles; so that, in fact,
birds are modified reptiles. The remarkable genus

16

ADDRESS TO BRITISH ASSOCIATION, 1881.

Peripatus, so well studied by Moseley, tends to connect the annulose and articulate types.
Again, the structural resemblances between Amphioxus and the Ascidians had been pointed out by
Goodsir; and Kowalevsky in 1866 showed that
these were not mere analogies, but indicated a real
affinity. These observations, in the words of Allen
Thomson, 'have produced a change little short of
revolutionary in embryological and zoological views,
leading as they do to the support of the hypothesis
that the Ascidian is an earlier stage in the phylogenetic history of the mammal and other vertebrates/
The larval forms which occur in so many groups,
and of which the Insects afford us the most familiar
examples, are, in the words of Quatrefages, embryos
which lead an independent life. In such cases as
these, external conditions act upon the larvse as they
do upon the mature form; hence we have two classes
of changes, adaptational or adaptive, and developmental. These and many other facts must be taken
into consideration; nevertheless naturalists are now
generally agreed that embryological characters are of
high value as guides in classification, and it may, I
think, be regarded as well-established that, just as
the contents and sequence of rocks teach us the past
history of the earth, so is the gradual development of
the species indicated by the structure of the embryo
and its developmental changes.

THE GASTKiEA THEORY.

17

When the supporters of Darwin are told that his
theory is incredible, they may fairly ask why it is
impossible that a species in the course of hundreds
of thousands of years should have passed through
changes which occupy only a few days or weeks in
the life-history of each individual ?
The phenomena of yolk-segmentation, first observed
by Prevost and Dumas, are now known to be, in some
form or other, invariably the precursors of embryonic
development: while they reproduce, as the first
stages in the formation of the higher animals, the
main and essential features in the life-history of the
lowest forms. The ' blastoderm/ as it is called, or
first germ of the embryo in the egg, divides itself
into two layers, corresponding, as Huxley has
shown, to the two layers into which the body of the
Ccelenterata may be divided. Not only so, but most
embryos at an early stage of development have the
form of a cup, the walls of which are formed by the
two layers of the blastoderm. Kowalevsky was the
first to show the prevalence of this embryonic form,
and subsequently Lankester and Haeckel put forward
the hypothesis that it was the embryonic repetition
of an ancestral type, from which all the higher forms
are descended. The cavity of the cup is supposed
to be the stomach of this simple organism, and
the opening of the cup the mouth. The inner layer
of the wall of the cup constitutes the digestive
B

1& ADDKESS TO BRITISH ASSOCIATION, 1881.
membrane, and the outer the skin* To this form
Haeckel gave the name Gastrsea. It is, perhaps,
doubtful whether the theory of Lankester and
Haeckel can be accepted in precisely the form they
propounded i t ; but it has had an important influence on the progress of embryology. I cannot
quit the science of embryology without alluding
to the very admirable work on ' Comparative
Embryology' by our new general secretary, Mr.
Balfour, and also the 'Elements of Embryology'
which he had previously published in conjunction
with Dr. M. Foster.
In 1842 Steenstrup published his celebrated work
on the ' Alternation of Generations,' in which he
showed that many species are represented by two
perfectly distinct types or broods, differing in form,
structure, and habits; that in one of them males
are entirely wanting, and that the reproduction is
effected by fission, or by buds, which, however, are in
some cases structurally indistinguishable from eggs.
Steenstrup's illustrations were mainly taken from
marine or parasitic species, of very great interest, but
not generally familiar, excepting to naturalists. It
has since been shown that the common Cynips or
Gallfly is also a case in point. It had long been
known that in some genera belonging to this group,
males are entirely wanting, and it has now been shown
by Bassett, and more thoroughly by Adler, that some

ALTERNATION OF GENERATIONS.

19

of these species are double-brooded; the two broods
having been considered as distinct genera.
Thus an insect known as Neuroterus lenticularis,
of which females only occur, produces the familiar oakspangles so common on the under-sides of oak-leaves,
from which emerge, not Neuroterus lenticularis,
but an insect hitherto considered as a distinct species,
belonging even to a different genus, Spathegaster
baccarum. In Spathegaster both sexes occur; they
produce the currant-like galls found on oaks, and
from these galls Neuroterus is again developed. So
also the King Charles oak-apples produce a species
known as Teras terminalis, which descends to the
ground, and makes small galls on the roots of the oak.
From these emerge an insect known as Biorhiza aptera,
which again gives rise to the common oak-apple.
Many butterflies, again, are dimorphic, existing
under two, or even three, distinct forms—one that of
the winter, the other of the summer brood or broods.
Weismann has adduced strong reasons for thinking
that during the glacial period these species were onebrooded only, and existed in the present winter form;
that, as the climate improved, the period of warmth
became sufficient to allow the development of a second
brood, and led to the gradual rise of the summer form.
He and Edwards have shown that, while, by the
application of cold, pupae, which would naturally have
produced the summer form, can be made to assume the
B 2

20

ADDRESS TO BRITISH ASSOCIATION, 1881.

winter dress; it is, on the contrary, far more difficult
to change the winter into the summer colouring.
In some cases—as for instance in the very curious
Leptodora crystallina (a fresh-water crustacean, inhabiting deep lakes and reservoirs, and which, as its
name denotes, is almost perfectly transparent)—
though the two forms are almost exactly similar in
their mature state, the mode of development is very
different: for, while the winter form goes through a
well-marked metamorphosis, in the summer brood
the development is direct.
It might seem that such enquiries as these could
hardly have any practical bearing. Yet it is not improbable that they may lead to very important results.
For instance, it would appear that the fluke which
produces the rot in sheep, passes one phase of its
existence in snails or slugs, and we are not without
hopes that the researches, in which our lamented
friend Prof. Eolleston was engaged at the time of his
death, and which Mr. Thomas is continuing, will
lead, if not to the extirpation, at any rate to the
diminution, of a pest from which our farmers have so
grievously suffered.
It was in the year 1839 that Schwann and Schleiden
demonstrated the intimate relation in which animals
and plants stand to each other, by showing the identity
of the laws of development of the elementary parts in
the two kingdoms of organic nature. Analogies

INCREASE IN NUMBER OF SPECIES.

21

indeed had been previously pointed out; the presence
of cellular tissue in certain parts of animals was
known, but Caspar F. Wolff's brilliant memoir had
been nearly forgotten; and the tendency of microscopical investigation had rather been to encourage
the belief that no real similarity existed; that the
cellular tissue of animals was essentially different
from that of plants. This had arisen chiefly, perhaps,
because fully formed tissues were compared, and it
was mainly the study of the growth of cells which
led to the demonstration of the general law of development for all organic elementary tissues.
As regards descriptive biology, by far the greater
number of species now recorded have been named and
described within the last half-century, and it is not
too much to say that not a day passes without adding
new species to our lists. A comparison, for instance,
of the edition of Cuvier's ' Eegne Animal/ published
in 1828, as compared with the present state of our
knowledge, is most striking.
Dr. Gunther has been good enough to make a
calculation for me. The numbers, of course, are only
approximate, but it appears that while the total number of animals described up to 1831 wag not more
than 70,000, the number now is at least 320,000,
Lastly, to show how large a field still remains for
exploration, I may add that Mr. Waterhouse estimates
that our Museums contain not fewer than 12,000

22

ADDRESS TO BRITISH ASSOCIATION, 1881.

species of insects which have not yet been described,
while our collections do not probably contain anything
like one-half of those actually in existence. Further
than this, the anatomy and habits even of those
which have been described offer an inexhaustible field
for research, and it is not going too far to say that
there is not a single species which would not amply
repay the devotion of a lifetime.
One remarkable feature in the modern progress of
biological science has been the application of improved
methods of observation and experiment; and the employment in physiological research of the exact measurements employed by the experimental physicist.
Our microscopes have been greatly improved : achromatic object-glasses were introduced by Lister in
1829; the binocular arrangement by Wenham in
1856; while immersion lenses, first suggested by
Amici, and since carried out under the formula of
Abbe, are most valuable. The use of chemical reagents in microscopical investigations has proved
most instructive, and another very important method
of investigation has been the power of obtaining
very thin slices by imbedding the object to be
examined in paraffin or some other soft substance.
In this manner we can now obtain, say, fifty separate
sections of the egg of a beetle, or the brain of a bee.
At the close of the last century, Sprengel published
a most suggestive work on flowers, in which he

KELATION BETWEEN PLANTS AND INSECTS. 23
pointed out the curious relation existing between
these and insects, and showed that the latter carry
the pollen from flower to flower. His observations,
however, attracted little notice until Darwin called
attention to the subject in 1862. It had long been
known that the cowslip and primrose exist under
two forms, about equally numerous, and differing
from one another in the arrangements of their
stamens and pistils; the one form having the
stamens on the summit of the flower and the stigma
half-way down; while in the other the relative
positions are reversed, the stigma being at the summit
of the tube and the stamens half-way down. This
difference had, however, been regarded as a case of
mere variability; but Darwin showed it to be a
beautiful provision, the result of which is that insects
fertilise each flower with pollen brought from a
different plant; and he proved that flowers fertilised
with pollen from the other form yield more seed than
if fertilised with pollen of the same form, even if
taken from a different plant.
Attention having been thus directed to the
question, an astonishing variety of most beautiful
contrivances have been observed and described by
many botanists, especially Hooker, Axel, Delpino,
Hildebrand, Bennett, Fritz Muller, and above all
Hermann Muller and Darwin himself. The general
result is that to insects, and especially to bees, we

24 ADDRESS TO BRITISH ASSOCIATION, 1881,
owe the beauty of our gardens, the sweetness of our
fields. To their beneficent, though unconscious
action, flowers owe their scent and colour, their
honey—nay, in many cases, even their form. Their
present shape and varied arrangements, their brilliant
colours, their honey, and their sweet scent are all
due to the selection exercised by insects.
In these cases the relation between plants and
insects is one of mutual advantage. In many
species, however, plants present us with complex
arrangements adapted to protect them from insects ;
such, for instance, are in many cases the resinous
glands which render leaves unpalatable; the thickets
of hairs and other precautions which prevent flowers
from being robbed of their honey by ants. Again,
more than a century ago, our countryman, Ellis,
described an American plant, Dionaoa, in which the
leaves are somewhat concave, with long lateral
spines, and a joint in the middle, which closes up
with a jerk, like a rat-trap, the moment any unwary
insect alights on them. The plant, in fact, actually
captures and devours insects. This observation also
remained as an isolated fact until within the last few
years, when Darwin, Hooker, and others have shown
that many other species have curious and very
varied contrivances for supplying themselves with
animal food*
As regards the progress of botany in other

SYSTEMATIC BOTANY.

25

directions, Mr. Thiselton Dyer has been kind enough
to assist me in endeavouring to place the principal
facts before you. Some of the most fascinating
branches of botany—morphology, histology, and
physiology scarcely existed before 1830. In the two
former branches the discoveries of von Mohl are preeminent. He first observed cell-division in 1835,
and detected the presence of starch in chlorophyllcorpuscles in 1837, while he first described protoplasm, now so familiar to us, at least by name, in
1846. In the same year Amici discovered the existence of the embryonic vesicle in the embryo sac,
which develops into the embryo when fertilised by
the entrance of the pollen-tube into the micropyle.
The existence of sexual reproduction in the lower
plants was doubtful, or at least doubted by some
eminent authorities, as recently as 1853, when the
actual process of fertilisation in the common bladderwrack of our shores was observed by Thuret, while
the reproduction of the larger fungi was first worked
out by De Bary in 1863.
As regards lichens, Schwendener proposed* in
1869, the startling theory, now however accepted by
some of the highest authorities, that lichens are not
autonomous organisms, but commensal associations
of a fungus parasitic on an alga. With reference to
the higher Cryptogams, it is hardly too much to say
that the whole of our exact knowledge of their life-

26

ADDEESS TO BEITISH ASSOCIATIOIST, 1881.

history has been obtained during the last halfcentury. Thus in the case of ferns the male organs,
or antheridia, were first discovered by Nageli in 1844,
and the archegonia, or female organs, by Suminski in
1848.
The early stages in the development of
mosses were worked out by Valentine in 1833.
Lastly, the principle of Alternation of Generations in
plants was discovered by Hofmeister. This eminent
naturalist also, in 1851—4, pointed out the homologies of the reproductive processes in mosses, vascular
cryptogams, gymnosperms, and angiosperms.
Geographical Botany can hardly be said to have
had any scientific status anterior to the publication
of the ' Origin of Species/ The way had been paved,
however, by A. de Candolle and the well-known
essay of Edward Forbes—' On the Distribution of the
Plants and Animals of the British Isles/—by Sir J.
Hooker's introductory essay to the 'Flora of New
Zealand/ and by Hooker and Thomson's introductory
essay to. the * Flora Indica/ One result of these
researches has been to give the coup de grace to the
theory of an Atlantis. Lastly, in a lecture delivered
to the Geographical Society in 1878, Thiselton Dyer
himself has summed up the present state of the
subject, and contributed an important addition to
our knowledge of plant-distribution by showing how
its main features may be explained by migration
in latitude from north to south without recourse

GEOGRAPHICAL BOTANY.

27

being had to a submerged southern continent for
explaining the features common to South Africa,
Australia, and America.
The fact that systematic and geographical botany
have claimed a preponderating share of the attention
of British phytologists, is no doubt in great measure
due to the ever-expanding area of the British Empire,
and the rich botanical treasures which we are continually receiving from India and our numerous
colonies. The series of Indian and Colonial Floras
published under the direction of the authorities at
Eew, and the ' Genera Plantarum' of Bentham and
Hooker, are certainly an honour to our country. To
similar causes we may trace the rise and rapid progress of economic botany, to which the late Sir W.
Hooker so greatly contributed.
In vegetable physiology some of the most striking
researches have been on the effect produced by rays
of light of different refrangibility. Daubeny, Draper,
and Sachs have shown that the light of the red end
of the spectrum is more effective than that of the
blue, so far as the decomposition of carbon dioxide
(carbonic acid) is concerned.
Nothing could have appeared less likely than that
researches into the theory of spontaneous generation
should have led to practical improvements in medical
science. Yet such has been the case. Only a few
years ago Bacteria seemed mere scientific curiosities.

28

ADDRESS TO BRITISH ASSOCIATION, 1881.

It had long been known that an infusion—say, of
hay—would, if exposed to the atmosphere, be found,
after a certain time, to teem with living forms.
Even those few who still believe that life would be
spontaneously generated in such an infusion, will
admit that these minute organisms are, if not
entirely, yet mainly, derived from germs floating in
our atmosphere; and if precautions are taken to
exclude such germs, as in the careful experiments
especially of Pasteur, Tyndall, and Koberts, everyone will grant that in ninety-nine cases out of a
hundred no such development of life will take place.
In 1836—7 Cagniard de la Tour and Schwann independently showed that" fermentation was no mere
chemical process, but was due to the presence of a
microscopic plant. But, more than this, it has been
gradually established that putrefaction is also the
work of microscopic organisms. Thirty years, however, elapsed before these important discoveries
received any practical application.
At length, however, these facts have led to most
important results in Surgery. One reason why
compound fractures are so dangerous is because, the
skin being broken, the air obtains access to the
wound, bringing with it innumerable germs, which
too often set up putrefying action* Lister first
made a practical application of these observations.
He set himself to find some substance capable of

MICRO-ORGANISMS CAUSES OF DISEASE.

29

killing the germs without being itself too potent a
caustic, and he found that dilute carbolic acid fulfilled these conditions. This discovery has enabled
many operations to be performed which would
previously have been almost hopeless.
The same idea seems destined to prove as useful
in Medicine as in Surgery. There is great reason to
suppose that many diseases, especially those of a
zymotic character, have their origin in the germs of
special organisms. We know that fevers run a certain
definite course. The parasitic organisms are at first
few, but gradually multiply at the expense of the
patient, and then die out again. Indeed, it seems to
be thoroughly established that many diseases are
due to the excessive multiplication of microscopic
organisms, and we are not without hope that means
will be discovered by which, without injury to the
patient, these terrible, though minute, enemies may
be destroyed, and the disease thus stayed. Bacillus
anthracis, for instance, is now known to be the cause
of splenic fever, which is so fatal to cattle, and is
also communicable to man. At Bradford, for instance,
it is only too well known as the wool-sorter's disease.
If, however, matter containing the Bacillus be treated
in a particular manner, and cattle be then inoculated
with it, they are found to acquire an immunity from
the fever. The interesting researches of BurdonSanderson, Greenfield, Koch, Pasteur, Toussaint, and

30

ADDEESS TO BRITISH ASSOCIATION, 1881.

others, seem to justify the hope that we may be able
to modify these and other germs, and then by
appropriate inoculation to protect ourselves against
fever and other acute diseases.
Ferrier's researches in continuation of those of
Fritsch and Hitzig have enabled us to localise the
function of various parts of the brain. His results
have not only proved of great importance in surgery,
and in many cases led to successful operations by
pointing out the exact source of the mischief, but an
exact knowledge of the brain is also of the greatest
importance in the treatment of nervous diseases.
Echeverria has collected 165 cases of traumatic
epilepsy, of which 64 per cent, were cured by removing a portion of the skull, the site for the operation
and the exact locality of the injury being indicated
by cerebral localisation.
The history of Anaesthetics is a most remarkable
illustration how long we may be on the very verge of
a most important discovery. Ether, which, as we all
know, produces perfect insensibility to pain, was
discovered as long ago as 1540. The anaesthetic
property of nitrous oxide, now so extensively used,
was observed in 1800 by Sir H. Davy, who actually
experimented on himself, and had one of his teeth
painlessly extracted when under its influence. He
even suggests t h a t ' as nitrous oxide gas seems capable
of destroying pain, it could probably be used with

PROGRESS m USE OF ANESTHETICS.

31

advantage in surgical operations/ Nay, this property
of nitrous oxide was habitually explained and illustrated in the chemical lectures given in hospitals,
and yet for fifty years the gas was never used in
actual operations. No one did more to promote the
use of anesthetics than Sir James Y. Simpson, who
introduced chloroform, a substance which was discovered in 1831, and which for a while almost
entirely superseded ether and nitrous oxide, though
with improved methods of administration, the latter
are now coming into favour again.
The only other reference to Physiology which time
permits me to make, is the great discovery of the
reflex action, as it is called, of the nervous centres.
Reflex actions had been long ago observed, and it
had been shown by Whytt and Hales that they were
more or less independent of volition. But the
general opinion was that these movements indicated
some feeble power of sensation independently of the
brain, and it was not till the year 1832 that the
' reflex' action' of certain nervous centres was made
known to us by Marshall Hall, and almost at the
same period by Johannes Muller.
Few branches of science have made more rapid
progress in the last half-century than that which
deals with the ancient condition of Man. When our
Association was founded it was generally considered

32

ADDRESS TO BRITISH ASSOCIATION, 1881.

that the human race suddenly appeared on the scene
about 6,000 years ago, after the disappearance of the
extinct mammalia, and when Europe, both as regards
physical conditions and the other animals by which
it was inhabited, was pretty much in the same state
as in the period covered by Greek and Eoman history.
Since then the persevering researches of Layard,
Eawlinson, Botta and others have made known to us
not only the statues and palaces of the ancient
Assyrian monarchs, but even their libraries; the
cuneiform characters have been deciphered, and we
can not only see, but read, in the British Museum,
the actual contemporary records, on burnt clay
cylinders, of the events recorded in the historical
books of the Old Testament and in the pages of
Herodotus. The researches in Egypt also seem to
have satisfactorily established the fact that the
pyramids themselves are at least 6,000 years old,
while it is obvious that the Assyrian and Egyptian
monarchies cannot suddenly have attained to the
wealth and power, the state of social organisation,
and progress in the arts, of which we have before us,
preserved by the sand of the desert from the ravages
of man, such wonderful proofs.
In Europe, the writings of the earliest historians
and poets indicated that, before iron came into
general use, there was a time when bronze was the
ordinary material of weapons, axes, and other cutting

THE BKONZE AND STONE AGES.

33

implements, and though it seemed a priori improbable that a compound of copper and tin should
have preceded the simple metal iron, nevertheless
the researches of archaeologists have shown that
there really was in Europe a ' Bronze Age/ which
at the dawn of history was just giving way to that
of 'Iron/
The contents of ancient graves, buried in many
cases so that their owner might carry some at least
of his wealth with him to the world of spirits, have
proved very instructive. More especially the results
obtained by Nilsson in Scandinavia, by Hoare and
Borlase, Bateman, Greenwell, and Pitt Rivers, in our
own country, and the contents of the rich cemetery at
Hallstadt, left no room for doubt as to the existence
of a Bronze Age ; but we get a completer idea of the
condition of Man at this period from the Swiss lakevillages, first made known to us by Keller, and
subsequently studied by Morlot, Troyon, Desor,
Riitimeyer, Heer, and other Swiss archaeologists.
Along the shallow edges of the Swiss lakes there
flourished, once upon a time, many populous villages
or towns, built on platforms supported by piles,
exactly as many Malayan villages are now. Under
these circumstances innumerable objects were one by
one dropped into the water; sometimes whole villages
were burnt, and their contents submerged; and thus
we have been able to recover, from the waters of
c

34

ADDRESS TO BRITISH ASSOCIATION/ 1881.

oblivion in which they had rested for more than 2,000
years, not only the arms and tools of this ancient
people, the bones of their animals, their pottery and
ornaments, but the stuffs they wore, the grain they
had stored up for future use, even fruits and cakes of
bread.
But this bronze-using people were not the earliest
occupants of Europe. The contents of ancient tombs
give evidence of a time when metal was unknown.
This also was confirmed by the evidence then unexpectedly received from the Swiss lakes. By the side
of the Bronze-Age villages were others, not less
extensive, in which, while implements of stone
and bone were discovered literally by thousands,
not a trace of metal was met with. The shellmounds or refuse-heaps accumulated by the ancient
fishermen along the shores of Denmark, and carefully
examined by Steenstrup, Worsaae, and other Danish
naturalists, fully confirmed the existence of a 'Stone
Age.' '
We have still much to learn, I need hardly say,
about this Stone-Age people, but it is surprising how
much has been made out. Evans truly observes, in
his admirable work on * Ancient Stone Implements/
'that so far as external appliances are concerned,
they are almost as fully represented as would be
thoseof any existing savage nation, by the researches
of a painstaking traveller/ We have their axes, adzes,

THE BRONZE AND STONE AGES.

35

chisels, borers, scrapers, and various other tools, and
we know how they made and how they used them;
we have their personal ornaments and implements
of war; we have their cooking utensils; we know
what they ate and what they wore; lastly, we know
their mode of sepulture and funeral customs. They
hunted the deer and horse, the bison and urus, the
bear and the wolf, but the reindeer had already
retreated to the North.
No bones of the reindeer, no fragment of any of the
extinct mammalia have been found in any of the
Swiss lake-villages or in any of the thousands of
tumuli which have been opened in our own country
or in Central and Southern Europe. Yet the con^
tents of caves and of river-gravels afford abundant evidence that there was a time when the mammoth and
rhinoceros, the musk-ox and reindeer, the cave lion
and hyena, the great bear and the • gigantic Irish
elk wandered in our woods and valleys, and the
hippopotamus floated in our rivers; when England
and France were united, and the Thames and the
Rhine had a common estuary. This was long supposed to be before the advent of man. At length,
however, the discoveries of Boucher de Perthes in
the valley of the Somme, supported as they are by the
researches of many continental naturalists, and in
our own country of MacEnery and Godwin Austen,
Prestwich and Lyell, Vivian and Pengelly, Christy
c 2

36

ADDBESS TO BEITISH ASSOCIATION, 1881.

Evans, and many more have proved that man formed
a humble part of this strange assembly.
Nay, even at this early period there were at least
two distinct races of men in Europe ; one of them—
as Boyd-Dawkins has pointed out—closely resembling the modern Esquimaux in form, in his
weapons and implements, probably in his clothing, as
well as in so many of the animals with which he
was associated.
At this stage Man appears to have been ignorant
of pottery, to have had no knowledge of agriculture,
no domestic animals, except perhaps the dog. His
weapons were the axe, the spear, and the javelin; I
do not believe that he knew the use of the bow,
though he was probably acquainted with the lance.
He was, of course, ignorant of metal, and his stone
implements, though skilfully formed, were of quite
different shapes from those of the second Stone Age,
and were never ground. This earlier Stone period,
when man co-existed with these extinct mammalia,
is known as the Palaeolithic, or Early Stone Age, in
opposition to the Neolithic, or Newer Stone Age.
The remains of the mammalia which co-existed
with man in pre-historic times have been most carefully studied by Owen, Lartet, Rutimeyer, Falconer,
Busk, Boyd-Dawkins, and others. The presence of
the mammoth, the reindeer, and especially of the
musk-ox, indicates a severe, not to say an arctic,

ECCENTRICITIES OF CLIMATE.

37

climate—the existence of which, moreover, was
proved by other considerations; while, on the contrary, the hippopotamus requires considerable
warmth. How, then, is this association to be
explained ?
While the climate of the globe is, no doubt, much
affected by geographical conditions, the cold of the
glacial period was, I believe, mainly due to the eccentricity of the earth's orbit combined with the oblique
effects of precession of the ecliptic. The result of
the latter condition is a period of 21,000 years,
during one half of which the northern hemisphere is
warmer than the southern, while during the other
10,500 years the reverse is the case. At present we
are in the former phase, and there is, we know, a
vast accumulation of ice at the south pole. But
when the earth's orbit is nearly circular, as it is at
present, the difference between the two hemispheres
is not very great; while on the contrary, as the
eccentricity of the orbit increases, the contrast
between them increases also. This eccentricity is
continually oscillating within certain limits which
Groll and subsequently Stone have calculated for the
last million years. At present the eccentricity is *016
and the mean temperature of the coldest month in
London is about 40°. Such has been the state of
things for nearly 100,000 years; but before that
there was a period, beginning 300,000 years ago,

38

ADDRESS TO BRITISH ASSOCIATION, 1881.

when the eccentricity of the orbit varied from '26 to
•57. The result of this would be greatly to increase the effect due to the obliquity of the orbit;
at certain periods the climate would be much
warmer than at present, while at others the number of days in winter would be twenty more, and
of summer twenty less, than now, while the
mean temperature of the coldest month would be
lowered 20°. We thus get something like a date
for the last glacial epoch, and we see that it was
not simply a period of cold, but rather one of extremes, each beat of the pendulum of temperature
lasting for no less than 21,000 years. This explains
the fact that, as Morlot showed in 1854, the glacial
deposits of Switzerland, and, as we now know,
those ,of Scotland, are not a single uniform layer,
but a succession of strata indicating very different
conditions. I agree also with Croll and Geikie in
thinking that these considerations explain the
apparent anomaly of the co-existence in the same
gravels of arctic and tropical animals; the former
having lived in the cold, while the latter flourished
in the hot, periods.
, It is, I think, now well established that man inhabited Europe during the milder periods of the
glacial epoch. Some high authorities indeed consider that we have evidence of his presence in preglacial and even in Miocene times, but I confess that

GEOLOGICAL KESEARCHES.

39

I am not satisfied on this point. Even the more recent
period carries back the record of man's existence to
a distance so great as altogether to change our views
of ancient history.
Nor is it only as regards the antiquity and
material condition of man in pre-historic times that
great progress has been made. If time ; permitted I should have been glad to have dwelt on ,the
origin and development of language, of custom, and
of law. On all of these the comparison • of; the
various lower races, still inhabiting so large a portion
of the earth's surface, has thrown much light; while
even in the most cultivated nations we find survivals, curious fancies, and lingering ideas; the
fossil remains as it were of former customs and religions, embedded in our modern civilisation, like the
relics of extinct animals in the crust of the earth.
In geology the formation of our Association coincided with the appearance of LyelFs ' Principles of
Geology/ the first volume of which was published in
1830 and the second in 1832. At that time the received opinion was that the phenomena of Geology
could only be explained by violent periodical convulsions, and a high intensity of terrestrial energy
culminating in repeated catastrophes. Hutton and
Playfair had indeed maintained that such causes as
those now in operation, would, if only time enough

40

ADDRESS TO BRITISH ASSOCIATION, 1881.

were allowed, account for the geological structure of
the earth; nevertheless the opposite view generallyprevailed, until Lyell, with rare sagacity and great
eloquence, with a wealth of illustration and most
powerful reasoning, convinced geologists that the
forces now in action are powerful enough, if only
time be given, to produce results quite as stupendous
as those which Science records.
As regards statigraphical geology, at the time of
the first meeting of the British Association at York,
the strata between the carboniferous limestone and
the chalk had been mainly reduced to order and
classified, chiefly through the labours of William
Smith. But the classification of all the strata lying
above the chalk and below the carboniferous limestone respectively, remained in a state of the greatest
confusion. The year 1831 marks the period of the
commencement of the joint labours of Sedgwick and
Murchison, which resulted in the establishment of
the Cambrian, Silurian, and Devonian systems. Our
Pre-Cambrian strata have recently been divided by
Hicks into four great groups of immense thickness,
and implying a great lapse of time; but no fossils
have yet been discovered in them. Lyell's classification of the Tertiary deposits; the result of the
studies which he carried on with the assistance of
Deshayes, and others, was published in the third
volume of the 'Principles of Geology' in 1833

GEOLOGICAL RESEARCHES.

41

The establishment of Lyell's divisions of Eocene,
Miocene, and Pliocene, was the starting-point of a
most important series of investigations by Prestwich
and others of these younger deposits; as well as of
the post-tertiary, quaternary, or drift beds, which are
of special interest from the light they have thrown
on the early history of man.
A full and admirable account of what has recently
been accomplished in this department of science, especially as regards the palaeozoic rocks, will be found
in Etheridge's late address to the Geological
Society.
The thickness of the sedimentary strata implies an
enormous lapse of time, but the amount of subsequent destruction which has taken place is scarcely
less surprising. Ramsay, for instance, has shown
that in Wales from 9,000 to 11,000 feet of solid rock
have been removed from large tracts of country.
Faults or cracks there extend for miles, with the
strata on one side raised in some cases as much as
10,000 feet above the same strata on the other, and
yet there is not on the surface the slightest vestige
of this gigantic dislocation.
The long lines of escarpment again, which stretch
for miles across our country, and were long supposed
to be ancient coast lines, are now ascertained,
mainly through the researches of Whitaker, to be
due to the differential action of aerial causes.

42

ADDKESS TO BKITISH ASSOCIATION, 1881.

Before 1831 the only geological maps of this
country were William Smith's general and county
maps, published between the years 1815 and 1824.
In the year 1832 De la Beche made proposals to the
Board of Ordnance to colour the ordnance-maps
geologically, and a sum of 300/. was granted for the
purpose. Out of this small beginning grew the
important work of the Geological Survey.
The cause of slaty cleavage had long been one of
the great difficulties of geology. Sedgwick suggested that it was produced by the action of
crystalline or polar forces. According to this view
miles and miles of country, comprising great
mountain masses, were neither more nor less than
parts of a gigantic crystal. Sharpe, however, called
attention to the fact that shells and other fossils contained in slate rocks are compressed in a direction at
right angles to the planes of cleavage, as if the rocks
had been seized in the jaws of a gigantic vice.
Sorby first maintained that the cleavage itself was
due to pressure. He observed slate rocks containing
small plates of mica, and that the effect of pressure
would tend to arrange these plates with their flat
surfaces perpendicular to the direction of the pressure.
Tyndall has since shown that the presence of flat
flakes is not necessary. He proved by experiment
that pure wax could be made by pressure to split
into plates of great tenuity, which he attributes

THE PHYSICAL STRUCTURE OF THE EARTH. 43

mainly to the lateral sliding of the particles of the
wax over each other; and thus the result of pressure
on such a mass is to develop a fissile structure
similar to that produced in wax on a small scale,
or on a great one in the slate rocks of Cumberland
or Wales.
The difficult problem of the conditions under
which granite and certain other rocks were formed
was attacked by Sorby with great skill in a paper
read before the Geological Society in 1858. The
microscopic spaces in many minerals contain a liquid
which does not entirely fill the hollow, but leaves a
small vacuum ; and Sorby ingeniously pointed out
that the rock must have solidified at least at a temperature high enough to expand the liquid so as to
fill the cavity. Sorby's important memoir laid the
foundation of microscopic petrography, which is now
not only one of the most promising branches of
geological research, but which has been successfully
applied by Sorby himself, and by Maskelyne, to the
study of meteorites.
As regards the physical character of the earth, two
theories have been held : one, that of a fluid interior
covered by a thin crust; the other, of a practically
solid sphere. The former is now generally considered
by physicists to be untenable. Though there is still
much difference of opinion, the prevailing feeling on
the subject has been expressed by Professor. Le Conte,

44

ADDKESS TO BEITISH ASSOCIATION, 1881.

who says, ' the whole theory of igneous agencies—•
which is little less than the whole foundation of
theoretic geology—must be reconstructed on the
basis of a solid earth/
In 1837 Agassiz startled the scientific world by his
'Discours sur Fancienne Extension des Glaciers,'
in which, developing the observation already made
by Charpentier and Venetz, that boulders had been
transported to great distances, and that rocks far
away from, or high above, existing glaciers, are
polished and scratched by the action of ice, he boldly
asserted the existence of a ' glacial period/ during
which Switzerland and the North of Europe were
subjected to great cold and buried under a vast sheet
of ice.
The ancient poets described certain gifted mortals
as privileged to descend into the interior of the earth,
and have exercised their imagination in recounting
the wonders there revealed. As in other cases,
however, the realities of science have proved more
varied and surprising than the dreams of fiction. Of
the gigantic and extraordinary animals thus revealed
to us, by far the greatest number have been described
during the period now under review. For instance,
the gigantic Cetiosaurus was described by Owen in
1838, the Dinornis of New Zealand by the same distinguished naturalist in 1839, the Mylodon in the
same year, and the Archasopteryx in 1862.

PALEONTOLOGY.

45

In America, a large number of remarkable forms
have been discovered, mainly by Marsh, Leidy, and
Cope. Marsh has made known to us the Titanosaurus, of the American (Colorado) Jurassic beds,
which is, perhaps, the largest land animal yet known,
being a hundred feet in length, and at least thirty in
height, though it seems possible that even these vast
dimensions were exceeded by those of the Atlantosaurus. Nor must I omit the Hesperornis, described
by Marsh in 1872, as a carnivorous, swimming
ostrich, provided with teeth, which he regards as a
character inherited from reptilian ancestors; the
Ichthyornis, stranger still, with biconcave vertebrae
like those of fishes, and teeth set in sockets ; while
in the Eocene deposits of the Rocky Mountains the
same indefatigable palaeontologist, among other very
interesting remains, has discovered three new groups
of remarkable mammals, the Dinocerata, Tillodontia,
and Brontotheridse. He has also described a number
of small, but very interesting Jurassic mammalia,
closely related to those found in our Stonesfield Slate
and Purbeck beds, for which he has proposed a new
order, ' Prototheria/ Lastly, I may mention the curiously anomalous Reptilia from South Africa, which
have been made known to us by Professor Owen.
Another important result of recent palseontological research is the law of brain-growth. It is not
only in the higher mammalia that we find form

46

ADDRESS TO BRITISH ASSOCIATION, 1881.

with brains much larger than any existing, say, in
Miocene times. The rule is almost general that—as
Marsh has briefly stated it—'all tertiary mammals
had small brains.' We may even carry the generalisation further. The cretaceous birds had brains
one-third smaller than those of our own day, and
the brain-cavities of the Dinosauria of the Jurassic
period are much smaller than in any existing reptiles.
As giving, in a few words, an idea of the rapid
progress in this department, I may mention that
Morris's 'Catalogue of British Fossils,' published in
1843, contained 5,300 species; while that now in
preparation by Mr. Etheridge enumerates 15,000.
But if these figures show how rapid our recent
progress has been, they also very forcibly illustrate
the imperfection of the geological record, giving us,
I will not say a measure, but an idea, of the imperfection of the geological record. The number of all
the described recent species is over 300,000, but
certainly not half are yet on our lists, and we may
safely take the total number of recent species as
being not less than TOOjOOO.1 But in former times
there have been at the very least twelve periods, in
each of which by far the greater number of species
were distinct. True, the number of species was
1
In suggesting this figure I was anxious to keep well within
the mark. If I were writing now I should estimate the total
number of existing species at not less than 2,000,000.

PKOGRESS OF PALEONTOLOGY.

47

probably not so large in the earlier periods as at
present; but if we make a liberal allowance for this,
we shall have a total of more than 2,000,000 species,
of which about 25,000 only are as yet upon record; and
many of these are only represented by a few, some only
by a single specimen, or even only by a fragment.
The progress of palaeontology may also be marked
by the extent to which the existence of groups has
been, if I may so say, carried back in time. Thus I
believe that in 1830 the earliest known quadrupeds
were small marsupials belonging to the Stonesfield
Slate; the most ancient mammal now known is Microlestes antiquus from the Keuper of Wiirtemberg: the
oldest bird known in 1831 belonged to the period of
the London Clay, the oldest now known is the
Archseopteryx of the Solenhofen Slate, though it is
probable that some at any rate of the footsteps on
the Triassic rocks are those of birds. So again the
Amphibia have been carried back from the Trias
to the Coal-measures ; Fish from the Old Red Sandstone to the Upper Silurian; Reptiles to the Trias;
Insects from the Cretaceous to the Devonian;
Mollusca and Crustacea from the Silurian to the
Lower Cambrian. The rocks below the Cambrian,
though of immense thickness, have afforded no relics
of animal life, if we except the problematical Eozoon
Canadense, so ably studied by Dawson and Carpenter. But if palaeontology as yet throws no light

48

ADDRESS TO BRITISH ASSOCIATION, 1881.

on the original forms of life, we must remember that
the simplest and the lowest organisms are so soft and
perishable that they would leave ' not a wrack
behind/ I will not, however, enlarge on this branch
of science, because we shall have the advantage on
Friday of hearing it treated with the skill of a
master.
Passing to the Science of Geography, Mr. Clements
Markham has recently published an excellent summary of what has been accomplished during the
half-century.
As regards the Arctic regions, in the year 1830
the coast line of Arctic America was only very
partially known, the region between Barrow Strait
and the continent, for instance, being quite unexplored, while the eastern sides of Greenland and
Spitzbergen,. and the coasts of Nova Zembla, were
almost unknown. Now the whole coast of Arctic
America has been delineated, the remarkable
archipelago to the north has been explored, and no
less than seven north-west passages—none of them,
however, unfortunately of any practical value—have
been traced. The north-eastern passage, on the
other hand, so far at least as the mouths of the great
Siberian rivers, may perhaps hereafter prove of commercial importance. In the Antarctic regions,
Enderby and Graham Lands were discovered in

GEOGRAPHY.

49

1831-2, Balleny Islands and Sabrina Land in 1839,
while the fact of the existence of the great southern
continent was established in 1841 by Sir James Eoss,
who penetrated in 1842 to 78° 11', the southernmost
point ever reached.
In Asia, to quote from Mr. Markham, ' our officers
have mapped the whole of Persia and Afghanistan,
surveyed Mesopotamia, and explored the Pamir
steppe. Japan, Borneo, Siam, the Malay peninsula,
and the greater part of China have been brought more
completely to our knowledge. Eastern Turkestan
has been visited, and trained native explorers have
penetrated to the remotest fountains of the Oxus,
and the wild plateaux of Thibet. Over the northern
half of the Asiatic Continent the Eussians have displayed great activity. They have traversed the wild
steppes and deserts of what on old atlases was called
Independent Tartary, have surveyed the courses of
the Jaxartes, the Oxus, and the Amur, and have
navigated the Caspian and the Sea of Aral. They
have pushed their scientific investigations into the
Pamir and Eastern Turkestan, until at last the
British and Eussian surveys have been connected.'
Again, fifty years ago the vast central regions of
Africa were almost a blank upon our best maps. The
rudely drawn lakes and rivers in maps of a more
ancient date had become discredited. These maps
did not agree among themselves, the evidence upon
D

50

ADDRESS TO BRITISH ASSOCIATION, 1881.

which they were laid down could not be found, they
were in inany respects highly improbable, and they
seemed inconsistent with what had then been ascertained concerning the Niger and the Blue and White
Niles. At the date of which I speak, the Sahara
had been crossed by English travellers from the
shores of the Mediterranean ; but the southern desert
still formed a bar to travellers from the Cape, while
the accounts of traders and others who alone had entered the country from the eastern and western coasts
were considered to form an insufficient basis for a map.
Since that time the successful crossing of the
Kalahari desert to Lake Ngami has been the prelude
to an era of African discovery. Livingstone explored
the basin of the Zambesi, and discovered vast lakes
and waters which have proved to be those of the
higher Congo. Burton and Speke opened the way
from the West Coast, which Speke and Grant
pursued into and down the Nile, and Stanley down
the course of the middle and lower Congo ; while the
vast extension of Egyptian dominion has brought a
huge slice of equatorial Africa within the limits of
semi-civilisation. The western side of Africa has
been attacked at many points. Alexander and
Galton were among the first to make known to us
its western tropical regions immediately to the north
of the Cape Colony; the Ogowe has been explored;
the Congo promises to become a centre of trade, and

HYDBOGBAPHY.

51

the navigable portions of the Niger, the Gambia, and
the Senegal are familiarly known.
The progress of discovery in Australia has been as
remarkable as that in Africa. The interior of this
great continent was absolutely unknown to us fifty
years ago, but is now crossed through its centre by
the electric telegraph, and no inconsiderable portion
of it is turned into sheep-farms. It is an interesting
fact that General Sabine, so long one of our most
active officers, and who is still with us, though,
unfortunately his health has for some time prevented
him from attending our meetings, was born on the
very day that the first settler landed in Australia.
In hydrography our charts have been immensely
improved. The study of rivers and of the physical
geography of the sea may indeed almost be said to
have come into existence as a science during the last
fifty years, and in the words of Jansen, it was Maury
(
who, by his wind and current charts, his trade-wind,
storm, and rain charts, and last, but not least, by his
work on the physical geography of the sea, gave the
first great impulse to all subsequent researches/
But the progress in our knowledge of geography is,
and has been, by no means confined to the improvement of our maps, or to the discovery and description
of new regions of the earth ; it has extended to the
causes which have led to the present configuration of
the surface. To a great extent indeed this part of
D 2

52

ADDRESS-TO BRITISH ASSOCIATION, 1881.

the subject falls rather within the scope of geology,
but I may here refer, in illustration, to the distribution of lakes, the phenomena of glaciers, the formation of volcanic mountains, and the structure and
distribution of coral islands.
The origin and distribution of lakes is one of the
most interesting problems in physical geography.
That they are not scattered at random, a glance at
the map is sufficient to show. They abound in
mountain districts, are comparatively rare in equatorial regions, increasing in number as we go north,
so that in Scotland and the northern parts of America
they are sown broadcast.
Perhaps a priori the first explanation of the origin
of lakes which would suggest itself, would be that
they were formed in hollows resulting from a disturbance of the strata, which had thrown them into
a basin-shaped form. Lake-basins, however, of this
character are, as a matter of fact, very rare; as a
general rule lakes have not the form of basin-shaped
synclinal hollows, but, on the contrary, the strike of
the strata often runs right across them. My eminent
predecessor, Professor Ramsay, divides lakes into
three classes:—(1) Those which are due to irregular
accumulations of drift, and which are generally quite
shallow; (2) those which< are formed by moraines;
and (3) those which occupy true basins scooped by
glacier-ice out of the solid rock. To the latter class

THE ORIGIN OF LAKES.

53

belong, in his opinion, most of the great Swiss and
Italian lakes. Professor Eamsay attributes their
excavation to glaciers, because it is of course obvious
that rivers cannot make basin-shaped hollows surrounded by rock on all sides. Now the Lake of
Geneva, 1,230 feet, above the sea, is 984 feet deep,
the Lake of Brienz is 1,850 feet above the sea, and
2,000 feet deep, so that its bottom is really below
the sea level. The Italian lakes are even more
remarkable. The Lake of Como, 700 feet above the
sea, is 1,929 feet deep. Lago Maggiore, 685 feet
above the sea, is no less than 2,625 feet deep. It
will be observed that these lakes, like many others
in mountain regions—those of Scandinavia, for
instance—lie in the direct channels of the great old
glaciers. If the mind is at first staggered at the
magnitude of the scale, we must remember that the
ice which scooped out the valley in which the Lake
of Geneva now reposes, was once at least 2,700 feet
thick; while the moraines were also of gigantic
magnitude, that of Ivrea, for instance, being no less
than 1,500 feet in height. Professor Ramsay's
theory seems, therefore, to account beautifully for a
large number of interesting facts.
The problem is, however, very complex; and, while
admitting the force of Professor Ramsay's arguments,
there are, no doubt, other causes which have exercised a considerable influence in the arrangement and

54

ADDRESS TO BRITISH ASSOCIATION, 1881.

configuration of lakes; for instance—as has been ably
argued by. our new Secretary, Mr. Bonney—irregular
movements of upheaval along lines athwart the valleys.
Passing from lakes to mountains, two rival theories
with reference to the structure and origin of volcanoes
long struggled for supremacy.
The more general view was that the sheets of lava
and scorise which form volcanic cones—such, for
instance, as iEtna or Vesuvius—were originally
nearly horizontal, and that subsequently a force
operating from below, and exerting a pressure both
upwards and outwards from a central axis towards
all points of the compass, uplifted the whole stratified
mass and made it assume a conical form, giving rise
at the same time, in many cases, to a wide and deep
circular opening at the top of the cone, called by the
advocates of this hypothesis a ' crater of elevation/
This theory, though, as it seems to us now, it had
already received its death-blow from the admirable
memoirs of Scrope, was yet that most generally
adopted fifty years ago, because it was considered
that compact and crystalline lavas could not have
consolidated on a slope exceeding 1° or 2°. In 1858,
however, Sir C. Lyell conclusively showed that in
fact such lavas could consolidate at a considerable
angle, even in some cases at more than 30°, and it is
now generally admitted that though the beds of lava,
&c, may have sustained a slight angular elevation

VOLCANOES. GLACIERS.

55

since their deposition, still in the main, volcanic^
cones have acquired their form by the accumulation
of lava and ashes ejected from one or more craters.
The problems presented by glaciers are of very
great interest. In 1843 Agassiz and Forbes proved
that the centre of a glacier, like that of a river, moves
more rapidly than its sides. But how and why do
glaciers move at all ? Rendu, afterwards Bishop of
Annecj, in 1841 endeavoured to explain the facts by
supposing that glacier ice enjoys a kind of ductility.
The 'viscous theory' of glaciers was also adopted,
and most ably advocated by^ Forbes, who compared
the condition of a glacier to that of the contents of a
tar barrel poured into a sloping channel. We have
all, however, seen long narrow fissures, a mere fraction
of an inch in width, stretching far across glaciers—
a condition incompatible with the ordinary idea of
viscosity. The phenomenon of regelation was afterwards applied to the explanation of glacier-motion.
An observation of Faraday's supplied the clue. He
noticed in 1850 that when two pieces of thawing ice
are placed together they unite by freezing at the
place of contact. Following up this suggestion
Tyndall found that if he compressed a block of ice in
a mould it could be made to assume any shape he
pleased. A straight prism, for instance, placed in a
groove and submitted to hydraulic pressure, was bent
into a transparent semicircle of ice. These experi-

56

ADDRESS TO BRITISH ASSOCIATION, 1881.

ments seem to have proved that a glacial valley is a
mould through which the ice is forced, and to which
it will accommodate itself, while, as Tyndall and
Huxley also pointed out, the ' veined structure of ice'
is produced by pressure, in the same manner as the
cleavage of slate rocks.
It was in the year 1842 that Darwin published his
great work on ' Coral Islands/ The fringing reefs of
coral presented no special difficulty. They could be
obviously accounted for by an elevation of the land,
so that the coral which had originally grown under
water had been raised above the sea-level. The
circular or oval shape of so many reefs, however, each
having a lagoon in the centre, closely surrounded by
a deep ocean, and rising but a few feet above the sealevel, had long been a puzzle to the physical geographer. The favourite theory was that these were
the summits of submarine volcanoes on which the
coral had grown. But as the reef-making coral
does not live at greater depths than about twentyfive fathoms, the immense number of these reefs
formed an almost insuperable objection to this
theory. The Laccadives and Maldives, for i n s t a n c e meaning literally the * lac of islands' and the ' thousand islands'—are a series of such atolls, and it was
impossible to imagine so great a number of craters,
»all so nearly of the same altitude. Darwin showed,
moreover, that so far from the ring of corals resting

COKAL ISLANDS. ABYSSES OF THE OCEAN. 57

on a corresponding ridge of rocks, the lagoons, on the
contrary, now occupy the place which was once the
highest land. He pointed out that some lagoons, as
fof instance that of Vanikoro, contain an island in
the middle; while other islands, such as Tahiti, are
surrounded by a margin of smooth water separated
from the ocean by a coral reef. Now if we suppose
that Tahiti were to sink slowly, it would gradually
approximate to the condition of Vanikoro; and if
Vanikoro gradually sank, the central island would
disappear, while on the contrary the growth of the
coral might neutralise the subsidence of the reef, so
that we should have simply an atoll with its lagoon.
The same considerations explain the origin of the
' barrier reefs/ such as that which runs, for nearly one
thousand miles, along the north-east coast of Australia. Thus Darwin's theory explained the form
and the approximate identity of altitude of these
coral islands. But it did more than this, because it
showed us that there were great areas in process
of subsidence, which though slow, was of great
importance in physical geography.1
Much information has also been acquired with
reference to the abysses of the ocean, especially from
the voyages of the Porcvpine and the Challenger.
The greatest depth yet recorded is near the Ladrone
1
I ought, perhaps, to mention that Darwin's views have "been
recently questioned on some points by Semper and Murray.

58

ADDRESS TO BRITISH ASSOCIATION, 1881.

Islands, where a sounding of 4,575 fathoms was
obtained.
Ehrenberg long ago pointed out the similarity of
the calcareous mud now accumulating in our recent
seas to the chalk, and showed that the green sands of
the geologist are largely made up of casts of
Foraminifera. Clay, however, had been looked on,
until the recent expeditions, as essentially a product of
the disintegration of older rocks. Not only, however,
are a large proportion of siliceous and calcareous
rocks either directly or indirectly derived from
material which has once formed a portion of living
organisms, but Sir Wyville Thomson maintains that
this is the case with some clays also. In that case
the striking remark of Linnaeus, t h a t ' fossils are not
the children but the parents of rocks,' will have received remarkable confirmation. I should have
thought it, I confess, probable that these clays are, to
a considerable extent, composed of volcanic dust.
It would appear that calcareous deposits resembling
our chalk do not occur at a greater depth than 3,000
fathoms; they have not been met with in the abysses
of the ocean. Here the bottom consists of exceedingly fine clay, sometimes coloured red by oxide of
iron, sometimes chocolate by manganese oxide, and
containing with Foraminifera occasionally large
numbers of siliceous Eadiolaria. These strata seem
to accumulate with extreme slowness : this is inferred

ASTRONOMY. SPECTRUM ANALYSIS.

59

from the comparative abundance of whales' bones
and fishes' teeth; and from the presence of minute
spherical particles, supposed by Mr. Murray to be of
cosmic origin—in fact, to be the dust of meteorites
which in the course of ages have fallen on the ocean.
Such particles no doubt occur over the whole surface
of the earth, but on land they soon oxidise, and in
shallow water they are covered up by other deposits.
Another interesting result of recent deep-sea explorations has been to show that the depths of the ocean
are no mere barren solitudes, as was until recent
years confidently believed, but, on the contrary, present us with many remarkable forms of life. We have,
however, as yet but thrown here and there a ray of
light down into the ocean abysses :—
Nor can so. short a time sufficient be
To fathom the vast depths of Nature's sea.

In Astronomy, the discovery in 1845 of the planet
Neptune, made independently and almost simultaneously by Adams and by Le Verrier, was certainly
one of the very greatest triumphs of mathematical
genius. Of the minor planets four only were known
in 1831, whilst the number now on the roll amounts
to 220. Many astronomers believe in the existence
of an intra-mercurial planet or planets, but this is
still an open question. The Solar System has also
been enriched by the discovery of an inner ring to

60

ADDRESS TO BRITISH ASSOCIATION, 1881.

Saturn, of satellites to Mars, and of additional
satellites to Saturn, Uranus, and Neptune.
The most unexpected progress, however, in our
astronomical knowledge during the past half-century
has been due to spectrum analysis, y
The dark lines in the Spectrum were first seen by
Wollaston, who noticed a few of them; but they
were independently discovered by Fraunhofer, after
whom they are justly named, and who, in 1814,
mapped no fewer than 576. The first steps in
' spectrum analysis/ properly so called, were made by
Sir J. Herschel, Fox Talbot, and by Wheatstone.
The latter, in a paper read before this Association in
1835, showed that the spectrum emitted by the
incandescent vapour of metals was formed of bright
lines, and that these lines, while, as he then supposed,
constant for each metal, differed for different metals.
' We have here/ he said, ' a mode of discriminating
metallic bodies more readily than that of chemical
examination, and which may hereafter be employed
for useful purposes/ Nay, not only can bodies thus
be more readily discriminated, but, as we now know,
the presence of extremely minute portions can be
detected, the sooioo^ °f a grain being in some cases
easily perceptible.
It is also easy to see that the presence of any new
simple substance might be detected, and in this
manner already several new elements have been

SPECTRUM ANALYSIS.

61

discovered, as I shall mention when we come to
Chemistry.
But spectrum analysis has led to even grander and
more unexpected triumphs.
Fraunhofer himself
noticed the coincidence between the double dark
line D of the solar spectrum and a double line which
he observed in the spectra of ordinary flames, while
Stokes pointed out to Sir W. Thomson, who taught
it in his lectures, that in both cases these lines were
due to the presence of sodium. To Kirchhoff and
Bunsen, however, is due the independent conception
and the credit of having first systematically investigated the relation which exists between Fraunhofer's
lines and the bright lines in the spectra of incandescent metals. In order to get some fixed measure
by which they might determine and record the lines
characterising any given substance, it occurred to
them that they might use for comparison the
spectrum of the sun. They accordingly arranged
their spectroscope so that onerhalf of the slit was
lighted by the sun, and the other by the luminous
gases they proposed to examine. It immediately
struck them that the bright lines in the one corresponded with the dark lines in the other—the bright
line of sodium, for instance, with the line or rather
lines D in the sun's spectrum. The conclusion was
obvious. There was sodium in the sun. It must indeed have been a glorious moment when that

62

ADDRESS TO BRITISH ASSOCIATION, 1881.

thought flashed across them, and even by itself well
worth all their labour.
But why is the bright line of a sodium flame
represented by a black one in the spectrum of the
sun ? To Angstrom is due the theory that a vapour
or gas can absorb luminous rays of the same refrangibility only as those which it emits when highly
heated; while Balfour Stewart independently discovered the same law with reference to radiant heat.
This is the basis of Kirchhoff's theory of the origin
of Fraunhofer's lines. In the atmosphere of the sun
the vapours of various metals are present, each of
which would give its characteristic lines, but within
this atmospheric envelope is the still more intensely
heated nucleus of the sun, which emits a brilliant
continuous spectrum containing rays of all degrees of
refrangibility. "When the light of this intensely
heated nucleus is transmitted through the surrounding
atmosphere, the bright lines which would be produced
by this atmosphere are seen as dark ones.
Kirchhoff and Bunsen thus proved the existence
in the sun of hydrogen, sodium, magnesium, calcium,
iron, nickel, chromium, manganese, titanium, and
cobalt; since which Angstrom, Thalen, and Lockyer
have considerably increased the list.
But it is not merely the chemistry of the heavenly
bodies on which light is thrown by the spectroscope ;
their physical structure and evolutional history

THE CONSTITUTION OF THE gUN.

63

are also illuminated by this wonderful instrument
of research.
It used to be supposed that the sun was a dark
body enveloped in a luminous atmosphere. The reverse now appears to be the truth. The body of the
sun, or photosphere, is intensely brilliant; round it
lies the solar atmosphere of comparatively cool gases,
which cause the dark lines in the spectrum; thirdly,
the chromosphere,—a sphere principally of hydrogen,
jets of which are said sometimes to reach to a height
of 100,000 miles or more, into the outer coating or
corona, the nature of which is still very doubtful.
Formerly the red flames which represent the higher
regions of the chromosphere could be seen only on the
rare occasions of a total solar eclipse. Janssen and
Lockyer, by the application of the spectroscope have
enabled us to study this region of the sun at all times.
It is, moreover, obvious that the powerful engine
of investigation afforded us by the spectroscope is by
no means confined to the substances which form part
of our system. The incandescent body can thus be
examined, no matter how great its distance, so long
only as the light is strong enough. That this
method was theoretically applicable to the light of
the stars was indeed obvious, but the practical
difBculties were very great. Sirius, the brightest of
all, is, in round numbers, a hundred millions of
millions of miles from us; and, though as big as

64

ADDRESS TO BRITISH ASSOCIATION, 1881.

sixty of our suns, his light when it reaches us,
after a journey of sixteen years, is at most one twothousand-millionth part as bright. Nevertheless as
long ago as 1815 Fraunhofer recognised the fixed
lines in the light of four of the stars, and in 1863
Miller and Huggins in our own country, and Eutherford in America, succeeded in determining the dark
lines in the spectrum of some of the brighter stars,
thus showing that these beautiful and mysterious
lights contain many of the material substances with
which we are familiar. In Aldebaran, for instance,
we may infer the presence of hydrogen, sodium,
magnesium, iron, calcium, tellurium, antimony,
bismuth, and mercury; some of which are not yet
known to occur in the sun. As might have been expected, the composition of the stars is not uniform,
and it would appear that they may be arranged in
a few well-marked classes indicating differences
of temperature, or in other words, of age. Some
recent photographic spectra of stars obtained by
Huggius go very far to justify this view.
Thus we can make the stars teach us their own
composition with light which started from its source
in some cases before we were born—light older than
our Association itself.
Until 1864, the true nature of the unresolved
nebulse was a matter of doubt. In that year,
however, Huggins turned his spectroscope on to a

THE COMPOSITION OF STARS AND NEBULiE. 65

nebula, and made the unexpected discovery that the
spectra of some of these bodies are discontinuous—
that is to say, consist of bright lines only, indicating
t h a t ' in place of an incandescent solid or liquid body
we must probably regard these objects, or at least
their photo-surfaces, as enormous masses of luminous
gas or vapour. For it is from matter in a gaseous
state only that such light as that of the nebulae is
known to be emitted/ So far as observation has yet
gone, nebulae may be divided into two classes : some
giving a continuous spectrum, others one consisting
of bright lines. These latter all appear to give
essentially the same spectrum, consisting of a few
bright lines. Two of them, in Mr. Huggins's opinion,
indicate the presence of hydrogen: one of them agrees
in position with a line characteristic of nitrogen.
But spectrum analysis has even more than this to
tell us. The old methods of observation could determine the movements of the stars so far only as they
were transverse to u s ; they afforded no means of
measuring motion either directly towards or away
from us. Doppler suggested in 1841 that the
colours of the stars would assist us in this respect
because they would be affected by their motion to
and from the earth, just as the sound of a steamwhistle is raised or lowered as ifc approaches or
recedes from us. Everyone has observed that if a
train whistles as it passes us the sound appears to
E

66

ADDRESS TO BRITISH ASSOCIATION, 1881.

alter at the moment the engine goes by. This arises,
of course, not from any change in the whistle itself,
but because the number of vibrations which reach the
ear in a given time are increased by the speed of the
train as it approaches, and diminished as it recedes.
So, like the sound, the colour would be affected by
such a movement; but Doppler's method was practically inapplicable, because the amount of effect on the
colour would be utterly insensible; and even if it were
the method could not, for other reasons, be applied ;
indeed, as we did not know the true colour of the
stars we have no datum line by which to measure.
A change of refrangibility of light, however, does
occur in consequence of relative motion, and Huggins
successfully applied the spectroscope to solve the problem. He took in the first place the spectroscope of
Sirius, and chose a line known as F, which is due
to hydrogen. Now, if Sirius was motionless, or
rather if it retained a constant distance from the
earth, the line F would occupy exactly the same
position in the spectrum of Sirius as in that of
the sun. On the contrary, if Sirius were approaching or receding from us, this line would be slightly
shifted either towards the blue or red end of the
spectrum. He found that the line had moved very
slightly towards the red, indicating that the distance
between us and Sirius is increasing at the rate of
about twenty miles a second. So also Betelgeux,

SHOOTING STARS. COMETS.

67

Eigel, Castor, and Regulus are increasing their
distance, while, on the contrary, that of others as for
instance of Vega, Areturus, and Pollux, is diminishing. The results obtained by Huggins on about
twenty stars have since been confirmed and extended
by Mr. Christie, now Astronomer-Royal, in succession
to Sir G. Airy, who has long occupied the post with
so much honour to himself and advantage to science.
To examine the spectrum of a shooting star
would seem even more difficult. Alexander Herschel
first succeeded in doing so, and determined the presence of sodium; since which Von Konkoly has
recognised the lines of magnesium, carbon, potassium,
lithium, and other substances, and it appears that
the shooting stars are bodies similar in character and
composition to the stony masses which sometimes
reach the earth as aerolites.
Some light has also been thrown upon those
mysterious visitants, the comets. The researches of
Prof. Newton on the periods of meteoroids led to the
remarkable discovery by Schiaparelli of the identity
of the orbits of some meteor-swarms with those of
some comets. The similarity of orbits is too striking
to be the result of chance, and shows a true cosmical
relation between the bodies. Comets, in fact, are in
some cases at any rate groups of meteoric stones.
From the spectra of the small comets of 1866 and
1868, Huggins showed that part of their' light is
E 2

68

ADDRESS TO BRITISH ASSOCIATION, 1881.

emitted by themselves, and reveals the presence of
carbon in some form. A photographic spectrum of
the comet recently visible, obtained by the same
observer, is considered by him to prove that nitrogen,
probably in combination with carbon, is also present.
No element has yet been found in any meteorite,
which was not previously known as existing in the
earth, but the phenomena which they exhibit
indicate that they must have been formed under
conditions very different from those which prevail on
the earth's surface. I may mention, for instance,
the peculiar form of crystallised silica, called by,
Maskelyne, Asmanite ; and the whole class of meteorites, consisting of iron generally alloyed with nickel,
which Daubree terms Holosiderites. The interesting
o

discovery, however, by Nordenskiold, in 1870, at Ovifak,
of a number of blocks of iron alloyed with nickel and
cobalt, in connection with basalts containing disseminated iron, has, in the words of Judd, * afforded a
very important link, placing the terrestrial and extraterrestrial rocks in closer relations with one another/
We have as yet no sufficient evidence to justify a
conclusion as to whether any substances exist in the
heavenly bodies which do not occur in our earth,
though there are many lines which cannot yet be satisfactorily referred to any terrestrial element. On the
other hand, some substances which occur on our earth
have not yet been detected in the sun's atmosphere.

THE HEAT OF THE SUN.

69

Such discoveries as these seemed, not long ago,
entirely beyond our hopes. M. Comte, indeed, in
his ' Cours de Philosophie Positive/ as recently as
1842, laid it down as an axiom regarding the
heavenly bodies, that ' Nous concevons la possibilite
de determiner leurs formes, leurs distances, leurs
grandeurs et leurs mouvements, tandis que nous ne
saurions jamais etudier par aucun moyen leur composition chimique ou leur structure mineralogique/
Yet within a few years this supposed impossibility
has-been actually accomplished, showing how unsafe
it is to limit the possibilities of science.
It is hardly necessary to point out that, while the
spectrum has taught us so much, we have still even
more to learn. Why should some substances give
few, and others many, lines? Why should the
same substance give different lines at different temperatures? What are the relations between the
lines and the physical or chemical properties ?
We may certainly look for much new knowledge
of the hidden actions of atoms and molecules from
future researches with the spectroscope. It may
even, perhaps, teach us to. modify our views of the socalled simple substances. Prout, long ago, struck by
the remarkable fact that nearly all atomic weights
are simple multiples of the atomic weight of hydrogen, suggested that hydrogen must be the primordial
substance. Brodie's researches also naturally fell in

70

ADDKESS TO BRITISH ASSOCIATION, 1881.

with the supposition that the so-cailed simple substances are in reality complex, and that their
constituents occur separately in the hottest regions
of the solar atmosphere. Lockyer considers that his
researches lend great probability to this view. The
whole subject is one of intense interest, and we may
rejoice that it is occupying the attention, not only of
such men as Abney, Dewar, Hartley, Liveing, Roscoe7
and Schuster in our own country, but also of many
foreign observers.
When geology so greatly extended our ideas of past
time, the continued heat of the sun became a
question of greater interest than ever. Helmholtz
has shown that, while adopting the nebular hypothesis, we need not assume that the nebulous matter
was originally incandescent ; but that its present high
temperature may be, and probably is, mainly due to
gravitation between its parts. It follows that the
potential energy of the sun is far from exhausted, and
that with continued shrinking it will continue to give
out light and heat, with little, if any, diminution for
several millions of years.
Like the sand of the sea, the stars of heaven have
ever been used as effective symbols of number, and
the improvements in our methods of observation have
added fresh force to our original impressions. We
now know that our earth is but a fraction of one out
of at least 75,000,000 worlds.

INVISIBLE STARS. EXTINCT STABS.

71

But this is not all. In addition to the luminous
heavenly bodies, we cannot doubt that there are
countless others, invisible to us from their greater
distance, smaller size, or feebler light; indeed we
know that there are many dark bodies which now
emit no light or comparatively little. Thus in the
case of Procyon, the existence of an invisible body is
proved by the movement of the visible star. Again
I may refer to the curious phenomena presented by
Algol, a bright star in the head of Medusa. The
star shines without change for two days and thirteen
hours; then, in three hours and a half, dwindles from
a star of the second to one o£ the fourth magnitude ;
and then, in another three and a half hours, reassumes
its original brilliancy. These changes seem certainly
to indicate the presence of an opaque body, which
intercepts at regular intervals a part of the light
emitted by Algol.
Thus the floor of heaven is not only ' thick inlaid
with patines of bright gold/ but studded also with
extinct stars, once probably as brilliant as our own
sun, but now dead and cold, as Helmholtz tells us
that our sun itself will be, some seventeen millions
of years hence.
The connection of Astronomy with the history of
our planet has been a subject of speculation and
research during a great part of the half-century of
our existence. Sir Charles Lyell devoted some of

72

ADDRESS TO BRITISH ASSOCIATION, 1881.

the opening chapters of his great work to the subject.
Haughton has brought his very original powers to
bear on the subject of secular changes in climate, and
Croll's contributions to the same subject are of great
interest. Last, but not least, I must not omit to
make mention of the series of massive memoirs (I
am happy to say not yet nearly terminated) by
George Darwin on tidal friction, and the influence
of tidal action on the evolution of the solar system.
I may perhaps just mention, as regards telescopes,
that the largest reflector in 1830 wras Sir W. Herschel's
of 4 ft., the largest at present being Lord Eosse's of
6 ft.; asregardsrefractorsthelargestthen hada diameter
of 11 \ in., while your fellow-townsman Gooke carried
the size to 25 in., and Mr. Grubb, of Dublin, has just
successfully completed one of 27 in. for the Observatory of Vienna. It is remarkable that the two
largest telescopes in the world should both be Irish.
The general result of astronomical researches has
been thus eloquently summed up by Proctor:—c The
sidereal system is altogether more complicated and
more varied in structure than has hitherto been supposed ; in the same region of the stellar depths coexist stars of many orders of real magnitude; all
orders of nebulse, gaseous or stellar, planetary, ringformed, elliptical, and spiral, exist within the limits
of the galaxy; and lastly, the whole system is alive
with movements, the laws of which may one day be

THE VELOCITY OF LIGHT.

73

recognised, though at present they appear too
complex to be understood.'
We can, I think, scarcely claim the establishment
of the undulatory theory of light as falling within
the last fifty years; for though Brewster, in his
' Report on Optics/ published in our first volume,
treats the question as open, and expresses himself still
unconvinced, he was, I believe, almost alone in his
preference for the emission theory. The phenomena
of interference, in fact, left hardly any—if any—room
for doubt, and the subject was finally set at rest by
Foucault's celebrated experiments in 1850. According to the undulatory theory the velocity of light
ought to be greater in air than in water, while if the
emission theory were correct the reverse would be
the case. The velocity of light—186,000 miles in a
second—is, however so great that, to determine its
rate in air, as compared with that in water, might
seem almost hopeless. The velocity in air was, nevertheless, determined by Fizeau in 1849, by means of
a rapidly revolving wheel. In the following year
Foucault, by means of a revolving mirror, demonstrated that the velocity of light is greater in air than
in water—thus completing the evidence in favour of
the undulatory theory of light.
The idea is now gaining ground, that, as maintained by Clerk-Maxwell, light itself is an electro-

74

ADDRESS TO BRITISH ASSOCIATION, 1881.

magnetic disturbance, the luminiferous ether being
the vehicle of both light and electricity*
Wiinsch, as long ago as 1792, had clearly shown
that the three primary colours were red, green, and
violet,; but his results attracted little notice, and the
general view used to be that there were seven
principal colours—red, orange, yellow, green, blue,
indigo, and violet; four of which—namely orange,
green, indigo, and violet—were considered to arise
from mixtures of the other three. Red, yellow, and
blue were therefore called the primary colours, and it
was supposed that in order to produce white light
these three colours must always be present.
Helmholtz, however, again showed, in 1852, that a
colour to our unaided eyes identical with white, was
produced by combining yellow with indigo. At that
time yellow was considered to be a simple colour, and
this, therefore, was regarded as an exception to the
general rule, that a combination of three simple colours
is required to produce white. Again, it was, and
indeed still is, the general impression that a combination of blue and yellow makes green. This,
however, is entirely a mistake. Of course we all
know that yellow paint and blue paint make green
paint: but this results from absorption of light by
the semi-transparent solid particles of the pigments,
and is not a mere mixture of the colours proceeding
unaltered from the yellow and the blue particles;

T H E T H E O R Y OF COLOUR.

75

moreover, as can easily be shown by two sheets of
coloured paper and a piece of window glass, blue and
yellow light, when combined, do not give a trace of
green, but if pure would produce the effect of white.
Green, therefore, is after all not produced by a mixture of blue and yellow. On the other hand, ClerkMaxwell proved in 1860 that yellow could be produced
by a mixture of red and green, which put an end to
the pretensions of yellow to be considered as a primary
colour. From these and other considerations it would
seem, therefore, that the three primary colours—if such
an expression be retained—are red, green, and violet.
The existence of rays beyond the violet, though
almost invisible to our eyes,1 had long been demonstrated by their chemical action. Stokes, howTever,
showed in 1852 that their existence might be proved
in another manner, for that there are certain substances which, when excited by them, emit light
visible to our eyes. To this phenomenon he gave the
name of fluorescence. At the other end of the spectrum
Abney has recently succeeded in photographing a large
number of lines in the infra-red portion, the existence
of which was first proved by Sir William Herschel.
From the rarity, and in many cases the entire
absence, of reference to blue, in ancient literature,
1
I have since shown that some of the lower animals are capable
of perceiving the ultra-violet rays. See Ants, Bees, and Wasps,
p. 201.

76

ADDRESS TO BRITISH ASSOCIATION, 1881.

Geiger—adopting and extending a suggestion first
thrown out by Mr. Gladstone—has maintained that,
even as recently as the time of Homer, our ancestors
were blue-blind. Though for my part I am unable
to adopt this view, it is certainly very remarkable
that neither the Rigveda, which consists almost
entirely of hymns to heaven, nor the Zendavesta, the
Bible of the Parsees or fire-worshippers, nor the
earlier books of the Old Testament, nor the Homeric
poems, ever allude to the sky as blue.
On the other hand, from the dawn of poetry,.the
splendours of the morning and evening skies have
excited the admiration of mankind. As Ruskin says,
in language almost as brilliant as the sky itself, the
whole heaven, ' from the zenith to the horizon,
becomes one molten, mantling sea of colour and fire ;
every black bar turns into massy gold, every ripple
and wave into unsullied shadowless crimson, and
purple, and scarlet, and colours for which there are no
words in language, and no ideas in the mind—things
which can only be conceived while they are visible;
the intense hollow blue of the upper sky melting
through it all, showing here deep, and pure, and
lightness; there, modulated by the filmy, formless
body of the transparent vapour, till it is lost imperceptibly in its crimson and gold.'
But what is the explanation of these gorgeous
colours ? why is the sky blue ? and why are the sunrise

PHOTOGRAPHY.

77

and sunset crimson and gold ? It may be said that
the air is blue, but if so how can the clouds assume
their varied tints ? Briicke showed that very minute
particles suspended in water are blue by reflected
light. Tyndall has taught us that the blue of the
sky is due to the reflection of the blue rays by the
minute particles floating in the atmosphere. Now if
from the white light of the sun the blue rays are
thus selected, those which are transmitted will be
yellow, orange, and red. Where the distance is short
the transmitted light will appear yellowish. But as
the sun sinks towards the horizon the atmospheric
distance increases, and consequently the number of the
scattering particles. They weaken in succession the
violet, the indigo, the blue, and even disturb the proportions of green. The transmitted light under such
circumstances must pass from yellow through orange
to red, and thus, while we at noon are admiring the
deep blue of the sky, the same rays, robbed of their
blue, are elsewhere lighting up the evening sky with
all the glories of sunset.
Another remarkable triumph of the last halfcentury has been the discovery of photography. At
the commencement of the century Wedgwood and
Davy observed the effect produced by throwing the
images of objects on paper or leather prepared with
nitrate of silver, but no means were known by which
such images could be fixed. This was first effected

78

ADDRESS TO BRITISH ASSOCIATION, 1881.

by Niepce, but his processes were open to objections,
which prevented them from coming into general use,
and it was not till 1839 that Daguerre invented the
process which was justly named after him. Very
soon a further improvement was effected, by
our countryman Talbot. He not only fixed his
' Talbotypes' on paper—in itself a great convenience
—but, by obtaining a negative, rendered it possible
to take off any number of positive, or natural, copies
from one original picture. This process is the
foundation of all the methods now in use ; perhaps
the greatest improvements having been the use of
glass plates, first proposed by Sir John Herschel; of
collodion, suggested by Le Grey, and practically used
by Archer; and, more lately, of gelatine, the foundation of the sensitive film now growing into general
use in the ordinary dry-plate process. Not only
have a great variety of other beautiful processes been
invented, but the delicacy of the sensitive film has
been immensely increased, with the advantage,
among others, of diminishing greatly the time necessary for obtaining a picture, so that even an express
train going at full speed can now be taken. Indeed
with full sunlight -^^ of a second is enough, and in
photographing the sun itself -Q-O^-Q-O of a second
is sufficient.
We owe to Wheatstone the conception that the
idea of solidity is derived from the combination of

THE NATURE OF HEAT.

79

two pictures of the same object in slightly different
perspective. This he proved in 1833 by drawing
two outlines of some geometrical figure or other
simple object, as they would appear to either eye respectively, and placing them so that they might then be
seen, one by each eye. The ' stereoscope/ thus produced, has been greatly popularised by photography.
For 2,000 years the art of lighting had made little
if any progress. Until the close of the last century,
for instance, our lighthouses contained mere fires of
wood or coal, though the construction had vastly improved. The Eddystone lighthouse, for instance, was
built by Smeaton in 1759; but for forty years its light
consisted of a row of tallow candles stuck in a hoop.
The Argand lamp was the first great improvement,
followed by gas, and in 1863 by the electric light.
Just as light was long supposed to be due to the
emission of material particles, so heat was regarded
as a material, though ethereal, substance, which was
added to bodies when their temperature was raised.
Davy's celebrated experiment of melting two
pieces of ice by rubbing them against one another in
the exhausted receiver of an air-pump had convinced
him that the cause of heat was the motion of the
invisible particles of bodies, as had been long before
suggested by Newton, Boyle, and Hooke. Rumford
and Young also advocated the same view. Nevertheless, the general opinion, even until the middle of

80

ADDRESS TO BRITISH ASSOCIATION, 1881.

the present century, was that heat was due to the
presence of a subtle fluid known as ' caloric,' a theory
which is now entirely abandoned.
Melloni, by the use of the electric pile, vastly
increased our knowledge of the phenomena of radiant
heat. His researches were confined to the solid and
liquid forms of matter. Tyndall studied the gases in
this respect, showing that differences greater than
those established by Melloni existed between gases
and vapours, both as regards the absorption and
radiation of heat. He proved, moreover, that the
aqueous vapour of our atmosphere, by checking
terrestrial radiation, augments the earth's temperature, and he considers that the existence of tropical
vegetation—the remains of which now constitute our
coal-beds—may have been due to the heat retained
by the vapours which at that period were diffused in
the earth's atmosphere. Indeed, but for the vapour
in our atmosphere, a single night would suffice to
destroy the whole vegetation of the temperate regions.
Inspired by a contemplation of Graham Bell's
ingenious experiments with intermittent beams on
solid bodies, Tyndall took a new and original departure ; and regarding the sounds as due to changes
of temperature he concluded that the same method
would prove applicable to gases. He thus found
himself in possession of a new and independentmethod of procedure. It need perhaps be hardly

MECHANICAL EQUIVALENT OF HEAT.

81

added that, when submitted to this new test, his
former conclusions on the interaction of heat and
gaseous matter stood their ground.
The determination of the mechanical equivalent of
heat is mainly due to the researches of Mayer and
Jouje. Mayer, in 1842, pointed out the mechanical
equivalent of heat as a fundamental datum to be
determined by experiment. Taking the heat produced by the condensation of air as the equivalent of
the work done in compressing the air, he obtained a
numerical value of the mechanical equivalent of heat.
There was, however, in these experiments, one weak
point. The matter operated on did not go through a
cycle of changes. He assumed that the production
of heat was the only effect of the work done in
compressing the air. Joule had the merit of being
the first to meet this possible source of error. He
ascertained that a weight of 1 lb. would have to fall
772 feet in order to raise the temperature of 1 lb. of
water by 1° Fahr. Hirn subsequently attacked the
problem from the other side, and showed that if all
the heat passing through a steam engine was turned
into work, for every degree Fahr. added to the
temperature of a pound of water, enough work could
be done to raise a weight of 1 lb. to a height of 772
feet. The general result is that, though we cannot
create energy we may help ourselves to any extent
from the great storehouse of nature. Wind and

82

ADDKESS TO BEITISH ASSOCIATION, 1881.

water, the coal-bed and the forest, afford man an
inexhaustible supply of available energy. It used to
be considered that there was an absolute break
between the different states of matter. The continuity of the gaseous, liquid, and solid conditions
was first demonstrated by Andrews in 1862.
Oxygen and nitrogen have been liquefied independently, and at the same time, by Cailletet and
Eaoul Pictet. Cailletet also succeeded in liquefying
air, and soon afterwards hydrogen was liquefied by
Pictet under a, pressure of 650 atmospheres, and a
cold of 170° Cent, below zero. It even became
partly solidified, and he assures us that it fell on
the floor with 'the shrill noise of metallic hail/
Thus then it was shown experimentally that there
are no such things as absolutely permanent gases.
The kinetic theory of gases, now generally accepted,
refers the elasticity of gases to a motion of translation
of their molecules, and we are assured that in the case
of hydrogen at a temperature of 60° Fahr. they move
at an average rate of 6,225 feet in a second; while
as regards their size, Loschmidt, who has since been
confirmed by Stoney and Sir W. Thomson, calculates
that each is at most-g-o-o^1^ IFF of an inch in diameter.
We cannot, it would seem at present, hope for any
increase of our knowledge of atoms by any improvement in the microscope. With our present instruments we can perceive lines ruled on glass of 9 0 ^ 0 F t h

THE SIZE OF MOLECULES.

83

of an inch apart. But, owing to the properties of
light itself, the fringes due to interference begin to
produce confusion at distances of T 4 - ^ F , and in the
brightest part of the spectrum at little more than
-90-J-^-o-th they would make the obscurity more or less
complete. If indeed we could use the blue rays by
themselves, their waves being much shorter, the
limit of possible visibility might be extended to
T2WF0" I a n d as Helmholtz has suggested, this perhaps
accounts for Stinde having actually been able to
obtain a photographic image of lines only xrnnnnr*n
of an inch apart. It would seem then that, owing
to the physical characters of light, we can, as Sorby
has pointed out, scarcely hope for any great improvement so far as the mere visibility of structure is
concerned, though in other respects no doubt much
may be hoped for. At the same time, Dallinger and
Royston Pigott have shown that, so far as the mere
presence of simple objects is concerned, bodies of
even smaller dimensions can be perceived.
According to the views of Helmholtz, the smallest
particle that could be distinctly denned, when
associated with others, is about 8 0 ^ 0 0 t h of an inch.
Sorby estimates that a particle of albumen of this
size contains 125,000,000 of molecules. In the case
of such a simple compound as water the number
would be no less than 8,000,000,000.. Even, then, if
we could construct microscopes far more powerful
F 2

84

ADDKESS TO BRITISH ASSOCIATION, 1881.

than any we now possess, they would not enable us to
obtain by direct vision any idea of the ultimate molecules of matter, Sorby calculates that the smallest
sphere of organic matter which could be clearly defined
with our most powerful microscopes would contain
many millions of molecules of albumen and water, and
it follows that there may be an almost infinite number
of structural characters in organic tissues, which we
can at present foresee no mode of examining.
The science of Meteorology has made great progress;
the weather, which was formerly treated as a local
phenomenon, being now shown to form part of a vast
system of -mutually . dependent cyclonic and anticyclonic movements. The storm-signals issued at
our ports are very valuable to sailors, while the small
weather-maps, for which we are mainly indebted to
Francis Galton, and the forecasts, which anyone
can obtain . on application either personally or by
telegraph at the Meteorological Office, are also of
increasing^ utility.
Electricity in the year 1881 may be considered to
have just been ripe for its adaptation to practical purposes ; it was but a few years previously, in 1819,
that Oersted had discovered the deflective action of
the current on the magnetic needle, that Ampere
had laid the foundation of electro-dynamics, that
Schweizzer had devised the electric coil or multiplier,

ELECTRICITY. TELEGRAPHY.

85

and that Sturgeon had constructed the first electromagnet. It was in 1831 that Faraday, the prince of
pure experimentalists, announced his discoveries of
voltaic induction and magneto-electricity, which with
the other three discoveries constitute the principles
of nearly all the telegraph instruments now in use;
and in 1834 our knowledge of the nature of the
electric current had been much advanced by the
interesting experiment of Sir Charles Wheatstone,
proving the velocity of the current in a metallic conductor to approach that of the wave of light.
Practical applications of these discoveries were not
long in coming to the fore, and the first telegraph
line on the Great Western Eailway from Paddington
to West Drayton was set up in 1838. In America,
Morse is said to have commenced the development of
his recording instrument between the years 1832 and
1837, while Steinheil, in Germany, during the same
period was engaged upon his somewhat super-refined
ink-recorder, using for the first time the earth for
completing the return circuit; whereas in this
country Cooke and Wheatstone, by adopting the
more simple device of the double-needle instrument,
were the first to make the electric telegraph a practical institution. Contemporaneously with, or immediately succeeding these pioneers, we find in this
country Alexander Bain, Breguet in France, Schilling
in Russia, and Werner Siemens in Germany, the last

86

ADDRESS: TO. BRITISH ASSOCIATION, 1881.

having first, in 1847, among others, made use of
gutta-percha as an insulating medium for electric
conductors, and thus cleared the way for subterranean
and submarine telegraphy.
Four years later, in 1851, submarine telegraphy
became an accomplished fact through the successful
establishment of telegraphic communication between
Dover and Calais. Submarine lines followed in rapid
succession, crossing the English Channel and the
German Ocean, threading their way through the
Mediterranean, Black and Eed Seas, until in 1866,
after two abortive attempts, telegraphic communication was successfully established between the Old and
New Worlds, beneath the Atlantic Ocean.
In connection with this great enterprise, and with
many investigations and suggestions of a highly
scientific and important character, the name of Sir
William Thomson will ever be remembered. The
ingenuity displayed in perfecting the means of
transmitting intelligence through metallic conductors,
with the utmost despatch and certainty as regards
the record obtained between two points hundreds
and even, thousands of miles apart is truly surprising.
The instruments devised by Morse, Siemens, and
Hughes have also proved most useful.
Duplex and quadruplex telegraphy, one of the
most striking achievements of modern telegraphy
the result of the labours of several inventors, should

ELECTRICITY.

87

not be passed over in silence. It not only serves for
the simultaneous communication of telegraphic intelligence in both directions, but renders it possible
for four instruments to be worked irrespectively of
one another, through one and the same wire connecting two distant places.
Another more recent and perhaps still more wonderful achievement in modern telegraphy is the invention
of the telephone and microphone, by means of which
the human voice is transmitted through the electric
conductor, by mechanism that imposes through its
extreme simplicity. In this connection the names of
Reiss, Graham Bell, Edison, and Hughes are those
chiefly deserving to be recorded.
Whilst electricity has thus furnished us with the
means of flashing our thoughts by record or by voice
from place to place, its use is now gradually extending for the achievement of such quantitative effects
as the production of light, the transmission of
mechanical power, and the precipitation of metals.
The principle involved in the magneto-electric and
dynamo-electric machines, by which these effects are
accomplished, may be traced to Faraday's discovery
in 1831 of the induced current, but their realisation
to the labours of Holmes, Siemens, Pacinotti,
Gramme, and others. In the electric light, gaslighting has found a formidable competitor, which
appears destined to take its place in public illumina-

88

ADDRESS TO BRITISH ASSOCIATION, 1881.

tion, and in lighting large halls, works, &a, for which
purposes it combines brilliancy and freedom from
obnoxious products of combustion, with comparative
cheapness. The electric light seems also to threaten,
when sub-divided in the manner recently devised by
Edison, Swan, and others, to make inroads into our
dwelling-houses.1
By the electric transmission of power, we may
hope some day to utilise at a distance such natural
sources of energy as the Falls of Niagara, and to work
our cranes, lifts, and machinery of every description
by means of sources of power arranged at convenient
centres. To these applications the Brothers Siemens
have more recently added the propulsion of trains by
currents passing through the rails, the fusion in considerable quantities of highly refractory substances,
and the use of electric centres of light in horticulture
as proposed by Werner and William Siemens. By
an essential improvement by Faure of the Plante
Secondary Battery, the problem of storing electrical
energy appears to have received a practical solution,
the real importance of which is clearly proved by Sir
W. Thomson's recent investigation of the subject.
It would be difficult to assign the limits to which
this development of electrical energy may not be rendered serviceable for the purposes of man.
1
I leave this sentence as it stood.
been quickly verified!

The prophecy has indeed

MATHEMATICS.

89

As regards mathematics I have felt that it would
be impossible for me, even with the kindest help, to
write anything myself. Mr. Spottiswoode, however,
has been so good as to supply me with the following
memorandum.
In a complete survey of the progress of science during the
half-century which has intervened between our first and our
present, meeting, the part played by mathematics would form
no insignificant feature. To those indeed who are outside its
enchanted circle it is difficult to realise the intense intellectual
energy which actuates its devotees, or the wide expanse over
which that energy ranges. Some measure, however, of its
progress may perhaps be formed by considering, in one or two
cases, from what simple principles some of the great recent
developments have taken their origin.
Consider, for instance, what is known as the principle of
signs. In geometry we are concerned with quantities such as
lines and angles ; and in the old systems a proposition was
proved with reference to a particular figure. This figure
might, it is true, be drawn in any manner witnin certain
ranges of limitation; but if the limits were exceeded, a new
proof, and often a new enunciation, became necessary. Gradually, however, it came to be perceived {e.g. by Carnot, in his
'Geometrie de Position,') that some propositions were true
even when the quantities were reversed in direction, fience
followed a recognition of the principle (of signs) that every
line should be regarded as a directed line, and every angle as
measured in a definite direction. By means of this simple
consideration, geometry has acquired a power similar to that
of algebra, viz. of changing the signs of the quantities and
transposing their positions, so as at once, and without fresh
demonstration, to give rise to new propositions.
To take another instance. The properties of triangles, as
established by Euclid, have always been considered as legitimate elements of proof; so that, when in any figure two
triangles occur, their relations may be used as steps in a

90

ADDRESS TO B R I T I S H ASSOCIATION, 1881.

demonstration. But, within the period of which I am speaking,
other general geometrical relations, e.g. those of a pencil of rays,
or of their intersection with a straight line, have been recognised as serving a similar purpose. "With what extensive
results this generalisation has been attended, the Geometrie
Superieure of the late M. Chasles, and all the superstructure
built on Anharmonic Ratio as a foundation, will be sufficient
evidence.
Once more, the algebraical expression for a line or a plane
involves two sets of quantities, the one relating to the position
of any point in the line or plane, and the other relating to the
position of the line or plane in space. The former set alone
were originally considered variable, the latter constant. But as
soon as it was seen that either set might at pleasure be regarded
as variable, there was opened out to mathematicians the whole
field of duality within geometry proper, and the theory of
correlative figures which is destined to occupy a prominent
position in the domain of mathematics.
Not unconnected with this is the marvellous extension
which the transformation of geometrical figures has received
very largely from Cremona and the Italian School, and which
in the hands of our countrymen Hirst and the late Professor
Clifford, has already brought forth such abundant fruit. I n
this, it may be added, there lay—dormant, it is true, and long
unnoticed—the principle whereby circular may be converted
into rectilinear motion, and vice versa—a problem which until
the time of Peaucillier seemed so far from solution, that one
of the greatest mathematicians of the day thought that he had
proved its entire impossibility. I n the hands of Sylvester, of
Kempe, and others, this principle has been developed into a
general theory of link-work, on which the last word has not
yet been said.
If time permitted, I might point out how the study of
particular geometric figures, such as curves and surfaces, has
been in many instances replaced by that of systems of figures
infinite in number, and indeed of various degrees of infinitude.
Such, for instance, are Pliicker's complexes and congruencies.
I might describe also how Riemann taught us that surfaces

MATHEMATICS.

91

need not present simple extension without thickness ; but that,
without losing their essential geometric character, they may
consist of manifold sheets ; and thus our conception of space
and our power of interpreting otherwise perplexing algebraical
expressions, become immensely enlarged.
Other generalisations might be mentioned, such as the
principle of continuity, the use of imaginary quantities, the
extension of the number of the dimensions of space, the
recognition of systems in which the axioms of Euclid have no
place. But as these were discussed in a recent address, I need
not now do more than remind you that the germs of the great
calculus of Quaternions were first announced by their author,
the late Sir W. E. Hamilton, at one of our meetings.
Passing from geometry proper to the other great branch of
mathematical machinery, viz. algebra, it is not too much to
say that within the period now in review there has grown up
a modern algebra which to our founders would have appeared
like a confused dream, and whose very language and terminology would be as an unknown tongue.
Into this subject I do not propose to lead you far. But, as
the progress which has been made in this direction is certainly
not less than that made in geometry, I will ask your attention
to one or two points which stand notably prominent.
I n algebra we use ordinary equations involving one unknown quantity ; in the application of algebra to geometry
we meet- with equations, representing curves or surfaces, and
involving two, or three unknown quantities respectively ; in
the theory of probabilities, and in other branches of research,
we employ still more general expressions. Now the modern
algebra, originating with Cayley and Sylvester, regards all
these diverse expressions as belonging to bne and the same
family, and comprises them all under the same general term
' quantics.' Studied from this point of view, they all alike
give rise to a class of derivative forms, previously unnoticed,
but now known as invariants, covariants, canonical forms, etc.
By means of these, mathematicians have arrived not only at
many properties of the quantics themselves, but also, at their
application to physical problems. I t would be a long and

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ADDRESS TO BRITISH ASSOCIATION, 1881.

perhaps invidious task to enumerate the many workers in this
fertile field of research, especially in the schools of Germany
and of Italy; but it is perhaps the less necessary to do so,
because Sylvester, aided by a young and vigorous staff at
Baltimore, is welding many of these results into a homogeneous
mass in the classical memoirs which are appearing from time
to time in the American ' Journal of Mathematics/
In order to remove any impression that these extensions of
algebra are merely barren speculations of ingenious intellects,
I may add that many of these derivative forms, at least in
their elementary stages, have already found their way into
the text-books of mathematics ; and one class in particular,
known by the name of determinants, is now introduced as a
recognised method of algebra, greatly to the convenience of all
those who become master of its use.
In the extension of mathematics it has happened more than
once that laws have been- established so simple in form, and
so obvious in their necessity as scarcely to require proof.
And yet their application is often of the highest importance in
checking conclusions which have been drawn from other
considerations, as well as^ in leading to> conclusions which,
without their aid, might have been difficult of attainment.
The same thing has occurred also in physics ; and notably in
the recognition of what has been termed the 'Law of the
Conservation of Energy.'
Energy has been defined to be * The capacity, or power, of any
body, or system of bodies, when in a given condition, to do a
measurable quantity of work.- Such wTork may either change
the condition of the bodies in question, or it may affect other
bodies ; but in either case energy is expended by the agent
upon the recipient in performance of the work. The law then
states that the total amount of energy in the agents and
recipients taken together remains unaltered by the changes in
question.
Now the principle on which the law depends is this:—
' that every kind of change among the bodies may be expressed
numerically in one standard unit of change, viz., work done,
in such wise that the result of the passage of any system from

THE CONSERVATION OF ENERGY.

93

one condition to another may be calculated by mere additions
and subtractions, even when we do not know how the change
came about* This being so, all work done by a system may
be expressed as a diminution of energy of that system, and
all work done upon a system as an accession of energy.
Consequently, the energy lost by one system in performance
of work will be gained by another in having work done
upon it, and the total energy, as between the two systems,
will remain unchanged.
There are two cases, or conditions, of energy which,
although substantially the same, are for convenience regarded
separately. These may be illustrated by the following
example. "Work may be done upon a body, and energy
communicated to it, by setting it in motion, e.g. by lifting it
against gravity. Suppose this to be done by a spring and
detent; and suppose further the body, on reaching its highest
point, to be caught so as to rest at that level on a support.
Then, whether we consider the body at the moment of
starting, or when resting on the support, it has equally
received an accession of energy from the spring, and is therefore equally capable of communicating energy to a third body.
But m the one case this is due to the motion which it has
acquired, and in the other to the position at which it rests,
and to its capability of falling again when the support is
removed. Energy in the first of these states is called * Energy
of Motion,' or ' Kinetic Energy,' and that in the second state*
'Energy of Position,' or 'Potential Energy.' In the case
supposed, at the moment of starting, the whole of the energy
is kinetic ; as the body rises, the energy becomes partly
potential and partly kinetic ; and when it reaches the highest
point the energy has become wholly potential. If the body
be again dropped, the process is reversed.
The history of a discovery, or invention, so simple at first
sight, is often found to be more complicated the more
thoroughly it is examined. That which at first seems to have
been due to a single mind proves to have been the result of
the successive actions of many minds. Attempts more or less
successful in the same direction are frequently traced out; and

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ADDRESS TO BRITISH ASSOCIATION, 1881.

even unsuccessful efforts may not have been without influence
on minds turned towards the same object. Lastly also, germs
of thought, priginally not fully understood, sometimes prove
in the end to have been the first stages of growth towards
ultimate fruit. The history of the law of the conservation of
energy forms no exception to this order of events. There are
those who discern even in the writings of Newton expressions
which show that he was in possession of some ideas which, if
followed out in a direct line of thought, would lead to those
now entertained on the subjects of energy and of work. But
however this may be, and whosoever might be reckoned
among the earlier contributors to the general subject of
energy, and to the establishment of its laws, it is certain that
within the period of which I am now speaking, the names of
Seguin, Clausius, Helmholtz, Mayer, and Colding on the
Continent, and those of Grove, Joule, Rankine, and Thomson
in this country, will always be associated with this great
work.
I must not, however, quit this subject without a passing
notice of a conclusion to which Sir William Thomson has
come, and in which he is followed by others who have pursued
the transformation of energy to some of its ultimate consequences. The nature of this will perhaps be most easily
apprehended by reference to a single instance. In a steam
engine, or other engine, in which the motive power depends
upon heat, it is well known that the source of power lies not
in the general temperature of the whole, but merely on the
difference of temperature between that of the boiler and that
of the condenser. And the effect of the condenser is to reduce
the steam issuing from the boiler to the same temperature as
that, of the condenser. When this is once done, no more
work can be got out of the engine, unless fresh heat be
supplied from an outside source to the boiler. The heat
originally communicated to the boiler has become uniformly
diffused, and the energy due to that difference is said to have
been dissipated. The energy remains in a potential condition
as regards other bodies ; but as regards the engine, it is of no
further use. Now suppose that we regard the entire material

CHEMISTRY.

95

universe as a gigantic engine, and that after long use we have
exhausted all the fuel (in its most general sense) in the world ;
then all the energy available will have become dissipated, and
we shall have arrived at a condition of things from which
there is no apparent escape. This is what is called the
' Dissipation of Energy.'

Prof. Frankland has been so good as to draw up for
me the following account of the progress of Chemistry
during the last half-century.
Most of the elements had been discovered before 1830, the
majority of the rarer elements since the beginning of the
century. In addition to these the following five have been
discovered, three of them by Mosander, viz. :—lanthanum in
1839, didymium in 1842, and ebrium in 1843. Ruthenium
was discovered by Claus in. 1843, and niobium by Rose in
1844. Spectrum analysis has added five to the list, viz. :—
Caesium and rubidium, which were discovered by Bunsen and
Kirchhoff in 1860 ; thallium, by Crookes in 1861 ; indium,
by Reich and Richter in 1863 ; and gallium, by Lecoq de
Boisbaudran in 1875.
As regards theoretical views, the atomic theory, the
foundation of scientific chemistry, had been propounded by
Dalton (1304-1808). The three laws which have been chiefly
instrumental in establishing the true atomic weights of the
elements—the law of Avogadro (1811), that equal volumes of
gases under the same conditions of temperature and pressure
contain equal numbers of molecules ; the law of Dulong and
Petit (1819), that the capacities for heat of the atoms of the
various elements are equal; and Mitscherlich's law of
isomorphism (1819), according to which equal numbers of
atoms of elements belonging to the same class may replace
each other in a compound without altering the crystalline
form of the latter, had been enunciated in quick succession ;
but the true application of these three laws, though in every
case distinctly stated by the discoverers, failed to be generally

96

ADDRESS TO BRITISH ASSOCIATION, 1881.

made, and it was not till the rectification of the atomic weights
by Cannizzaro, in 1858, that these important discoveries bore
fruit.
In organic chemistry the views most generally held about
the year 1830 were expressed in the radical theory of Berzelius.
This theory, which was first stated in its electro-chemical and
dualistic form by its author in 1817, received a further
development at his hands in 1834 after the discovery of the
benzoyl-radical by Liebigand Wohler. In the same year (1834),
however, a discovery was made by Dumas, which was
destined profoundly to modify the electro-chemical portion of
the theory, and even to overthrow the form of it put forth by
Berzelius. Dumas showed that an electro-negative element,
such as chlorine, might replace, atom for atom, an electropositive element like hydrogen, in some cases without much
alteration in the character of the compound. This law of
substitution has formed a necessary portion of every chemical
theory which has been proposed since its discovery, and its
importance has increased with the progress of the science. It
would take too long to enumerate all the theoretical views
which have prevailed at various times during the past fifty
years ; but the theory which along with the radical theory has
exercised most influence on the development of the views now
held, is the theory of types,, first stated by Dumas (1839) and
developed in a different form and amalgamated with the
radical theory by Gerhardt and Williamson (1848-1852). It
is, however, the less necessary to refer in detail to these views,
seeing that in the now prevailing theory of atomicity we
possess a generalisation which, while greatly extending the
scope of chemical science in its power of classifying known
and predicting unknown facts, includes all that was valuable
in the generalisations which preceded it. The study of the
behaviour of organo-metallic compounds in chemical reactions
led to the conclusion that various metallic elements possess a
definite capacity of saturation with regard to the number of
atoms of other elements with which they can combine, and
demonstrated this regularity of atom-fixing power in the case
of zinc, tin, arsenic and antimony. A serious obstacle,

ORGANIC AND INORGANIC SUBSTANCES.

97

however, in the way of determining the true atomicities of the
elements was the general employment of the old so-called
equivalent weights, which were by most chemists confounded
with the atomic weights. This difficulty was removed by the
rectification of the atomic weights, which, though begun by
Gerhardt as early as 1842, met for a long time with but little
recognition, and was not completed till the subject was taken
up by Cannizarro in 1858. The law of atomicity has given to
chemistry an exactness which it did not previously possess,
and since its discovery and recognition chemical research
has moved very much on the lines laid down by this law.
Chemists have been engaged in determining by means of
decompositions, the molecular architecture, or constitution as it
is called, of various compounds, natural and artificial, and in
verifying by synthesis the correctness of the views thus
arrived at.
It was long supposed that an impassable barrier existed
between inorganic and organic substances : that the chemist
could make the former in his laboratory, while the latter could
only be produced in the living bodies of animals or plants—
requiring for their construction not only chemical attractions,
but a supposed 'vital force.' It was not until 1828 that
Wohler broke down this barrier by the synthetic production
of urea, and since his time this branch of science in the hands
of Hofmann, Wurtz, Berthelot, Butlerow, and others, has
made great strides. Innumerable natural compounds have
thus been produced in the laboratory—ranging from bodies of
relatively simple constitution, such as the alcohols and acids
of the fatty series, to bodies of such complex molecular
structure as alizarin (the principal colouring matter of madder),
coumarin (the odoriferous principle of the tonqua bean),
vanillin, and indigo. The problem of the natural alkaloids
has also been attacked, in some cases with more than partial
success. Methylconine, which occurs along with conine in the
hemlock, has been recently prepared artificially by Michael
and Gundelach, this being the first instance of the synthesis of
a natural alkaloid. A proximate synthesis of atropine, the
alkaloid of the deadly nightshade, has been accomplished by
G

98

ADDRESS TO BRITISH ASSOCIATION, 1881.

Ladenburg. It seems further probable that at no distant date
the useful alkaloids, such as quinine, may also be synthesised,
inasmuch as quinoline, one of the products of the decomr
position of quinine, and of some of the allied bases, has
recently been prepared by Skraup by a method which admits
of its being obtained in any quantity.
Much also has been done in the way of building up compounds the existence of which was predicted by theory.
Indeed, the extent to which hitherto undiscovered substances
can be predicated is doubtless the greatest triumph achieved
by chemists during the past fifty years.
As yet, however, only the statical side of chemistry has been
developed. Whilst the physicist has been engaged in tracing,
for the gaseous condition at least, the paths of the molecules
and calculating their velocities, the chemist, whose business is
with the atoms within the molecule, can point to no such
scientific conquests. All that he knows concerning the intramolecular atoms, and all that he expresses in his constitutional
formula is, the particular relation of union in which each of
these atoms stands to the others—which of them are directly
united (as he expresses it) to other given atoms, and which of
them are in indirect union. Of the relative positions in space
occupied by these atoms, and of their modes of motion, he is
absolutely ignorant. In like manner in a chemical reaction
the initial and final conditions of the reacting substances are
known, but the intermediate stages—the modes of change—
are for the most part unexplained.
The feeling that no number, however great, of successfully
solved problems of constitutional chemistry (as at present
understood), and no number of syntheses, however brilliant,
of natural compounds could raise chemistry above the statical
stage—that the solution of the dynamical problem cannot be
arrived at by purely chemical means—has led many chemists
to approach the subject from the physical side. The results
which the physico-chemical methods, as exemplified in the
laws already alluded to of Dulong and Petit, Avogadro and
Mitscherlich, have yielded in the past, offer the best guarantee
of their success in the future. And the advantages of many of

PHYSICAL CHEMISTRY.

99

the physical methods are obvious. Every purely chemical examination—whether proximate or ultimate—of a compound,
presupposes the destruction of the substance under examination:
the chemist' murders to dissect.' But observations on the action
of a substance on the rays of light, on the relative volumes
occupied by molecular quantities of a substance, on its velocity
of transpiration in the liquid or gaseous state—these teach us the
habits of the living substance. The rays of light which have
threaded their way between the molecules of a body have
undergone, in contact with these molecules, various specific
and measurable changes, the nature and amount of which are
assuredly conditioned by the mass, form, and other properties
of the molecules : the plane of polarisation has been caused
to rotate ; a particular degree of refraction has been imparted ;
or rays of certain wave-lengths have been removed by absorption ; their absence being manifested by bands in the
absorption-spectrum of the substance. The volumes occupied
by molecular quantities are dependent partly on the size of
the molecules and partly on that of the intramolecular
spaces.
The duty of the physical chemist is to endeavour to
co-ordinate his physical observations with the known constitution of compounds, as already determined by the pure
chemist. This endeavour has in various branches of physical
chemistry been to some extent successful. Le Bel has found
that among organic compounds those only possess action on
the plane of polarised light which contain at least one
asymmetric carbon atom—that is to say, a carbon atom which
is united to four different atoms or groups of atoms. The
researches of Landolt, of Gladstone, and of Brahl on the
specific refraction of organic liquids, have shown that from the
known constitution of a liquid organic compound it is possible
to calculate its specific refraction. Noel Hartley, in an examination of the absorption-spectra of organic liquids for the
ultra-violet rays, has demonstrated that certain molecular
groupings are represented by particular absorption bands, and
this line of inquiry has been extended with very interesting
results to the ultra-red rays by Abney and Festing. It is
G 2

100 ADDRESS TO BRITISH ASSOCIATION, 1881.
obvious that these methods may in turn be employed to determine the unknown constitution of substances. The same
holds true of the investigations of Kopp with regard to the
molecular volumes of liquids at their boiling-points, in which
he has established the remarkable fact that some elements
always possess the same atomic volume in combination,
whereas, in the case of certain other elements, the atomic
volume varies in a perfectly definite manner with the mode of
combination. This investigation has lately been extended with
the best results by Thorpe, and by Ramsay. Thermo-chemistry
also, which for a long time, at least as regards that portion
which relates to the heat of formation of compounds, consisted
chiefly of a collection of single equations, each containing
three unknown quantities, is beginning to be interpreted by
Julius Thomsen, whose experienced work in this field is well
known. Many other methods of physico-chemical research
are being successfully prosecuted at the present day, but it
would go beyond the bounds of this summary even to
enumerate these.
The concordant results obtained by these widely differing
methods show that those chemists who have devoted themselves,
frequently amid the ridicule of their more practical brethren,
to ascertaining by purely chemical methods the constitution
of compounds, have not laboured in vain. But the future
doubtless belongs to physical chemistry.
In connection with the rectification of the atomic weights it
may be mentioned that a so-called natural system of the elements has been introduced by Mendelejeff (1869), in which the
properties of the elements appear as a periodic function of
their atomic weights. By the aid of this system it has been
possible to predict the properties and atomic weights of undiscovered elements, and in the case of known elements
to determine many atomic weights which had not been fixed
by any of the usual methods. Several of these predictions
have been verified in a remarkable manner. A periodicity in
the atomic weights of elements belonging to the same class
had been pointed out by Newlands about four years before the
publication of Mendelejeff's memoir.

MECHANICS.

101

In mechanical science the progress has not been
less remarkable than in other branches. Indeed to
the improvements in mechanics we owe no small part
of our advance in practical civilisation, and of the
increase of our national prosperity during the last
fifty years.
This immense development of mechanical science
has been to a great extent a consequence of the new
processes which have been adopted in the manufacture of iron, for the following data with reference to
which I am mainly indebted to Captain (now Sir)
Douglas Galton and Mr. Rendel. About 1830,
Neilson introduced the Hot Blast in the smelting
of iron. At first a temperature of 600° or 700°
Fahrenheit was obtained, but Cowper subsequently
applied Siemens' regenerative furnace for heating the
blast, chiefly by means of fumes from the black
furnace, which were formerly wasted; and the temperature now practically in use is as much as 1,400°, or
even more: the result is a very great economy of
fuel and an increase of the output. For instance, in
1830, a blast furnace with the cold blast would
probably produce 130 tons per week, whereas now,
600 tons a week are readily obtained.
Bessemer, by the brilliant discovery, which he first
brought before the British Association at Cheltenham
in 1856, showed that Iron and Steel could be produced
by forcing currents of atmospheric air through fluid

102 ADDRESS TO BRITISH ASSOCIATION, 1881.

pig metal, thus avoiding for the first time the intermediate process of puddling iron, and converting it by
cementation into steel. Similarly by Siemens' regenerative furnace, the pig metal and iron ore is
converted directly into steel, especially mild steel for
shipbuilding and boilers; and Whit worth, by his fluid
compression of steel, is enabled to produce steel in
the highest condition of density and strength of
which the metal is capable. These changes, by
which steel can be produced direct from the blast
furnace instead of by the more cumbersome processes
formerly in use, have been followed by improvements
in the manipulation of the metal.
The inventions of Cort and others were known
long before 1830, but we were then still without the
most powerful tool in the hands of the practical
metallurgist, viz., Nasmyth's steam-hammer.
Steel can how be produced as cheaply as iron was
formerly; and its substitution for iron as railway
material and in shipbuilding, has resulted in increased
safety in railway travelling, as well as in economy,
from its vastly greater durability. Moreover, the enlarged use of iron and steel, which has resulted from
these improvements in its make, has led to the adoption of mechanical means to supersede hand labour
in' almost every branch of trade and agriculture, by
which the power of production has been increased a
hundredfold, while at the same time much higher

IRON AND STEEL.

103

precision has been obtained. Sir Joseph Whitworth
has done more than any one else to perfect the
machinery of this country by the continued efforts
he has made, during nearly half-a-century,, to introduce accuracy into the standards of measurement in
use in workshops. He tells us that when he first
established his works, no two articles could be made
accurately alike or with interchangeable parts. He
devised a measuring apparatus, by which his workmen in making standard gauges are accustomed to
take measurements to the 215-^5- of an inch.
In its more immediate relation to the objects of
this Association, the increased importance of iron and
steel has led to numerous scientific investigations into
its mechanical properties and into the laws which
govern its strength; into the proper distribution of
the material in construction; and into the conditions
which govern the friction and adhesion of surfaces.
The names of Eaton Hodgkinson, Fairbairn, Barlow,
Rennie, Scott Russell, Willis, Fleeming Jenkin, and
Galton are prominently associated with these inquiries.
The introduction of iron has, moreover, had a vast
influence on the works of both the civil and military,
engineer. Before 1830, Telford had constructed an
iron suspension turnpike-road bridge of 560 feet over
the Menai Straits; but this bridge was not adapted
to the heavy weights of locomotive engines. At the
present time, with steel at his command, Mr. Fowler

104 ADDRESS TO -BRITISH ASSOCIATION, 1881.

is engaged in carrying out the design for a railway
bridge over the Forth, of two spans of 1,700 feet
each; that is to say, of nearly one-third of a mile in
length. In artillery, bronze has given place to
wrought iron and steel; the 68-pound shot which was
the heaviest projectile fifty years ago, with its range
of about 1,200 yards, is being replaced by a shot of
nearly a quarter-ton weight, with a range of nearly
five miles: and the armour-plates of ships are daily
obtaining new developments.
But it is in railroads, steamers, and the electric
telegraph that the progress of mechanical science has
most strikingly contributed to the welfare of man.
As regards railways, the Stockton and Darlington
Eailway was opened in 1825, but the Liverpool and
Manchester Eailway, perhaps the first truly passenger
line, dates from 1830, while the present mileage
of railways is over 200,000 miles, costing nearly
4,000,000,0002. sterling. It was not until 1838 that
the Sirius and Great Western first steamed across the
Atlantic. The steamer, in fact, is an excellent
epitome of the progress of the half-century; the
paddle has been superseded by the screw ; the compound has replaced the simple engine ; wood has
given place to iron, and iron in its turn to steel.
The saving in dead weight, by this improvement
alone, is from 10 to 16 per cent. The speed has
been increased from 9 knots to 15, or even more.

ECONOMIC SCIENCE.

105

Lastly, the steam-pressure has been increased from
less than 5 lbs. to 70 lbs. per square inch, while the
consumption of coal has been brought down from 5
or 6 lbs. per horse-power to less than 2. It is a
remarkable fact that not only is our British shipping
rapidly on the increase, but it is increasing relatively
to that of the rest of the world. In 1860 our tonnage
was 5,700,000 against 7,200,000 ; while it may now
be placed as 8,500,000 against 8,200,000 ; so that considerably more than half the whole shipping of the
world belongs to this country.1
If I say little with reference to economic science and
statistics it is because time, not materials, are wanting.
I scarcely think that in the present state of the
question I can be accused of wandering into politics
if I observe that the establishment of the doctrine of
free trade as a scientific truth falls within the period
under review.
In education some progress has been made towards
a more rational system. When I was a boy, neither
science, nor modern languages, nor arithmetic formed
any part of the public school system of the country.
This is now happily changed. Much, however, still
remains to be done. Too little time is still devoted
to French and German, and it is much to be re1

According to the last returns the figures are 9,100,000 tons
against 8,500,000.

106 ADDRESS TO BRITISH ASSOCIATION, 1881.

gretted that even in some of our best schools they
are taught as dead languages. Lastly, with few exceptions, only one or two hours a week on an average,
are devoted to science. We have, I am sure, none
of us any desire to exclude, or discourage, literature.
What we ask is that, say, six hours a week each
should be devoted to mathematics, modern languages,
and science—an arrangement which would still leave
twenty hours for Latin and Greek. I admit the
difficulties which schoolmasters have to contend
with; nevertheless, when we consider what science
has done and is doing for us, we cannot but consider
that our present system of education is, in the
words of the Duke of Devonshire's Commission,
' little less than a national misfortune/
In Agriculture the changes which have occurred in
the period since 1831 have been immense. The last
half-century has witnessed the introduction of the
modern system of subsoil drainage founded on the experiments of Smith of Deanston. The thrashing and
drilling machines were the most advanced forms of
machinery in use in 1831. Since then there have been
introduced the steam-plough; the mowing-machine;
the reaping-machine, which not only cuts the corn
but binds it into sheaves; while the steam-engine
thrashes out the grain and builds the ricks. Science
has thus greatly reduced the actual cost of labour,
and yet it has increased the wages of the labourer.

INTERCONNECTION OE THE SCIENCES.

107

It was to the British Association, at Glasgow, in
1841, that Baron Liebig first communicated his work
' O n the Application of Chemistry to Vegetable Physiology/ while we have also from time to time
received accounts of the persevering and important
experiments which Mr. Lawes, with the assistance of
Dr. Gilbert, has now carried on for more than forty
years at Rothamsted, and which-have given so great
an impulse to agriculture by directing attention to
the principles of cropping, and by leading to the
more philosophical application of manures.
' I feel that in quitting Section F so soon, I owe an
apology to our fellow-workers in that branch of
science, but I doubt not that my shortcomings will
be more than made up for by the address of their
excellent President, Mr. Grant-Duff, whose appointment to the Governorship of Madras, while occasioning so sad a loss to his friends, will unquestionably
prove a great advantage to India, and materially
conduce to the progress of science in that country.
Moreover, several other subjects of much importance, which might have been referred to in connection with these latter Sections, I have already
dealt with under their own more purely scientific
aspect.
Indeed, one very marked feature in modern discovery is the manner in which distinct branches of
science have thrown, and are throwing, light on one

108 ADDRESS TO BRITISH ASSOCIATION, 1881.

another. Thus the study of geographical distribution
of living beings, to the knowledge of which our late
general secretary, Mr. Sclater, has so greatly contributed, has done much to illustrate ancient geography.
The existence of high northern forms in the Pyrenees
and Alps indicates the existence of a period of cold
when Arctic species occupied the whole of habitable
Europe. Wallace's line—as it has been justly
named after that distinguished naturalist—points to
the very ancient separation between the Malayan and
Australian regions: and the study of corals has
thrown light upon the nature and significance of
atolls and barrier-reefs.
In studying the antiquity of man, the archaeologist
has to invoke the aid of the chemist, the geologist,
the physicist, and the mathematician. The recent
progress in astronomy is greatly due to physics and
chemistry. In geology the composition of rocks is a
question of chemistry and physics; the determination
of the boundaries of the different formations falls
within the limits of geography; while palaeontology
is the biology of the past.
And now I must conclude. I fear I ought to
apologise to you for keeping you so long, but still
more strongly do I wish to express my regret that
there are almost innumerable researches of great
interest and importance which fall within the last
fifty years (many even among those with which our

SUMMARY,

109

Association has been connected) to which I have
found it impossible to refer. Such, for instance, are,
in biology alone, Owen's memorable report on the
homologies of the vertebrate skeleton, Carpenter's
laborious researches on the microscopic structure of
shells, the reports on marine zoology by Allman,
Forbes, Jeffreys, Spence Bate, Norman, and others;
on Kent's Cavern by Pengelly; those by Duncan on
corals; Woodward on Crustacea; Carruthers, Williamson, and others on fossil botany, and many more.
Indeed no one who has not had occasion to study the
progress of science throughout its various departments can have any idea how enormous—how
unprecedented—the advance has been.
Though it is difficult, indeed impossible, to
measure exactly the extent of the influence exercised
by this Association, no one can doubt that it has
been very considerable. For my own part, I must
acknowledge with gratitude how much the interest
of my life has been enhanced by the stimulus of our
meetings, by the lectures and memoirs to which I
have had the advantage of listening, and above all,
by the many friendships which I owe to this
Association.
Summing up the principal results which have
been attained in the last half-century we may mention (over and above the accumulation of facts), the
theory of evolution, the antiquity of man, and the

110 ADDRESS TO BRITISH ASSOCIATION, 1881.

far greater antiquity of the world itself; the correlation of physical forces and the conservation of
energy; spectrum analysis and its application to
celestial physics ; the higher algebra and the modern
geometry; lastly, the innumerable applications of
science to practical life—as, for instance, in photography, the locomotive engine, the electric telegraph,
the spectroscope, and most recently the electric light
and the telephone.
To Science, again, we owe the idea of progress.
The ancients, says Bagehot, 'had no conception of
progress; they did not so much as reject the idea;
they did not even entertain it/ I t is not, I think,
going too far to say that the true test of the civilisation of a nation must now be measured by its
progress in science. It js often said, however, that
great and unexpected as the recent discoveries have
been, there are certain ultimate problems which
must ever remain unsolved. For my part, I would
prefer to abstain from laying down any such limitations. When Park asked the Arabs what became
of the sun at night, and whether the sun was always
the same, or new each day, they replied that such a
question was childish, and entirely beyond the reach
of human investigation. I have already mentioned
that, even as lately as 1842, so high an authority as
Comte treated as obviously impossible and hopeless
any Attempt to determine the chemical composition

SUMMARY.

Ill

of the heavenly bodies. Doubtless there are questions
the solution of which we do not as yet see our way
even to attempt; nevertheless the experience of
the past warns us not to limit the possibilities of the
future.
But however this may be, though the progress
made has been so rapid, and though no similar period
in the world's history has been nearly so prolific of
great results, yet, on the other hand, the prospects of
the future were never more encouraging. We must
not, indeed, shut our eyes to the possibility of failure ;
the temptation to military ambition; the tendency
to over-interference by the State; the spirit of
anarchy and socialism; these and other elements of
danger may mar the fair prospects of the future.
That they will succeed in doing so, I cannot believe.
I cannot but feel confident that fifty years hence,
when perhaps the city of York may renew its hospitable invitation, my successor in this chair—
more competent, I trust, than I have been to do justice to so grand a theme— will have to record a
series of discoveries even more unexpected and more
brilliant than those which I have attempted to
bring before you this evening; for assuredly one
great lesson which science teaches is—how little we
yet know, and how much we have still to learn.

RICHARD CLAY & SONS,

LIMITED,

LONDON A N D BUNGAY.