PROFESSOR TYNDALL'S ADDRESS.

Thames Star, Volume VII, Issue 1964, 21 April 1875, Page 4

PROFESSOR TYNDALL'S ADDRESS.

Address delivered "before the British Association, assembled at Belfast, with additions, hy John TgndaU, F.R.S., President. London: lonwmans, G-eeen, and Co., 1874.

[COHTIHTOBD.] Bishop Butler accepted with unwavering trust the chronology of the Old i Testament, describing it as ' confirmed by the natural and civil history of the world, collected from common historians, from the state of the earth, and from the late inventions of arts and sciences.' These words mark progress ; and they must seem somewhat hoary to; the Bishop's successors of to-day. (1) :It is hardly necessary to inform you that since his time the domain of the naturalist has been immensely extended—the whole science ef geology, with its astounding revelations regarding the- life of the ancient earth, having been created. The rigidity of old conceptions has been relaxed, the public mind being rendered gradually tolerant of the idea that not for six thousand, nor for sixty thousand, nor for six thousand thousand thousand, but for asohs embracing untold millions of years, this earth has been the theatre of life and death. The riddle of the rocks has been read by the geologist and palaeontologist, from subcambrian depths to the deposits thickening over the seabottoms of to-day. And upon the leaves of that stone book are, as you know, stamped the characters, plainer and surer than those formed/by the ink of history, which carry the iuind back into abysses of past time compared with which the periods which siatisfied Bishop Butler cease to have a visual angle. The lode of discovery once struck, those petrified forms in which life was at •one: time*active increased to multitudes, afld demanded classification. They were grouped in genera, species, and varieties, according to the'degree of similarity subsisting between them. Thus confusion •was avoided, each object being found in the pigeon-hole appropriated to it and to its fellows of similar morphological or physiological character. The general fact soon became evident that none but the simplest forms of life lie lowest down, that as we climb higher among the superimposed strata more peffect'fornis appear. The change, however, from form 'to form was not continuous, but by steps —some, small, some great,, . ' A section,' says Mr Huxley, 'a hundred, feet thick will exhibit at different heights a dozen species of Ammonite*, none of which passes beyond its particular zone of limestone, or clay, into the zone below it,. or into that above it.' In the presence of such facts it was not possible to avoid the. question: —Have these, forms, showing, though in broken stages and with many irregularities, this unmistakable general advance, been subjected to no, continuous law of growth or variation? Had our education been purely scientific, or had it been sufficiently detached from influences which, however ennobling in another domain, have always proved hindrances and delusions when introduced as factors into the domain of physics, the scientific mind never could laave swerved from the search for a law of growth, or allowed itself to accept the anthropomorphism which regarded ea.ch successive stratum as a kind of mechanic's bench for the manufacture of new. species out of all relation to the old.. '. ■

Biassed,, however, by tyheir previous education, the great majority of naturalists invoked a special creative act to account for the appearance ]of each new group of Organiainas. Doubtless there ■were numbers who were clear-headed enough to see that this was no explanation at afl; iihat in point of fact it was an attempt, by the introduction of a greater difficulty to account for a less. But having nothing to offer in the way of explanation, they for the most part held their peace. Still the thoughts of reflecting men naturally and necessarily limmered round the question. De Maillet, a contemporary. of Newton, has been brought into notice by Professor Huxley as one who 'had a notion of the modifiability of living forms.' In my frequent conversations with him, the late Sir Benjamin Brodie, a man of highly philosophic mind, often drew my attention to the fact that, as early as 1794, Charles Darwin's grandfather was the pioneer of Charles Darwin. '(2!) In 1801, and in subsequent years, tho celebrated Lamarck, who produced so profound an impression on the public mind, through the vigorous exposition of his views by the author of the ' Vestiges of Creation,' endeavoured to show the development of species out of changes of habit and external condition. In 1813 Dr. Wells, the founder of o»r present theory of Dew, read before the Koyal Society a paper in which, to use the words of Mr Darwin, 'he distinctly recognises the principle of natural selection ; and thisi is the first recognition that has been indicated.' The thoroughness and skill with which Wells pursued his work, and the obvious independence of his character, rendered him long ago a favourite with me; and it gave me the liveliest pleasure to alight upon this additional testimony to his penetration. Professor Grant, Mr Patrick Matthew, Yon Buch, the author of the • Vestiges,' D'Halloy, and others (3), by the enunciation of opinions more or less clear and correct, showed that the question had been fermenting long^ prior to the year 1858, when Mr Darwin and Mr Wallace simultaneously but independently placed their closely concurrent views upon the subject before the Linnean Society. ,; ''. .., These papers were followed in 1859 by the publication of the first edition of ' The Origin of Species.' All great things come, slowly to the birth. Copernicus, as I informed you, pondered his great work for thirty-three years. " Newton for nearly twenty years kept the idea of Gravitation before Ms mind; for twenty years alsO he dwelt upon his discovery of Fluxions, and doubtless would have continued to make it tike object of his private thought had he not/ound that Leibnitz was upon his track, Darwin for two and twenty years pondered the problem of the origin of species, arid doubtless he would have continued to do so had he not found Wallace upon his track. (4) A concentrated but full ancl powerful epitome of his labours was the consequence;. The book was by no means an easy one; and probably not one in. every score of those

(1) Only to some; for there are dignitaries who even now speak of the earth's, rocky crust as so much building material prepared for man at the Creation. Surely it is time that this loose language should cease. (2) Zoonomia. vol. i. pp. 500—510. (3) In 1855 Mr Herbert Spencer (Principles of Psychology, 2nd edit. vol.. i. p. 465) expressed 'the belief that life under all its forms has arisen by an unbroken evolution, and through the instrumentality of what are called natural causes.'

(4) The behaviour of Mr Wallace in relation to this subject has been dignified in the highest degree.

who (hen attacked it had read its pages through, or were competent to grasp their significance if they had. I do not say this merely to discredit them; for there were in those days some really eminent scientific men, entirely raised above the heat of popular prejudice.willing to accept any conclusion that science had to offer, provided it was duly backed by fact and argument, and who entirely mistook Mr Darwin's views. In fact, the work needed an expounder; and it found one in Mr Huxley. I know nothing more admirable in the way of scientific exposition than those early articles of his on the origin of species. He swept the curve of discussion through the really significant points'of the subject, enriched his exposition with profound original remarks and reflections, often summing up in a single pithy sentence an argument • which a less compact mind would have spread over pages. But there is one impression made by the book itself which no exposition of it, however luminous, can convey; and that is, the impression of the vast amount of labour, both of observation and of thought, implied in its production. Let us glance at its principles. It is conceded on all hands that what are called varieties are continually produced. The rule is probably without exception. ~No chick and no child is in all respects and particulars the counterpart of its brother and sister; and in such differences we have 'variety' incipient. No naturalist could tell how far this variation could be carried ; but the great mass of them held that never by any amount of internal or external change, nor by the mixturee of both, could the offspring of the same progenitor so far deviate from each other as to constitute different species. The function of the experimental philosopher is to combine the conditions of nature and to produce her results ; and this was the method of Darwin. (1) He made himself acquainted with what could, without any manner of doubt, be done in the way of producing variation, He associated himself with pigeon-fanciers—bought, begged, kept, and observed every breed that he could obtain. Though derived from a common stock, the diversities of these pigeons were such that' a score of them might be chosen, which, if shown to an ornithologist, and he were told that they were wild birds, would certainly be ranked by him as well-defined species.' The simple principle which guides the pigeon-fancier, as it does the cattle-breeder, is the selection of some variety that strikes his fancy, i and the propagation of; this variety -byi inheritance. With his eye still directed to the particular appearance which he wishes to exaggerate, he selects itifis it reappears in successive broods, and thus adds increment to increment, until an astonishing amount of divergence from the parent type is effected. The breeder in this case does not produce the elements of the variation. He simply observes them, and by selection adds them together until the required result has been obtained. ' Woman,' says Mr Darwin, * would ever try to make a fantail till he saw a pigeon with a tail developed in some slight degree in an unusual manner, or a pouter until he saw a pigeon with a crop of unusual size.' Thus nature gives the hint, man acts upon it, and by the law of inheritance exaggerates the deviation.

Having thus satisfied himself by indubitable facts that the organization of an animal or of a plant (for precisely the same treatment applies to plants) is to some extent plastic, he passes from variation under domestication to variation under nature. Hitherto we have dealt with the adding together of small changes by the conscious selection of man. Can Nature thus select? Mr Darwin's answer is, (Assuredly she can.' The number of living things produced is far in excess of the number that can be supported ; hence at some period or other of their lives there must be a struggle for existence; and what is the infallible result? If one organism were a perfect copy of the order in regard to strength, skill, and agility, external conditions would decide; But this is not the case. Here we have the fact of variety offering itself to nature, as in the former instance it offered itself to man; and those varieties which are least competentto cope with surrounding conditions will infallibly.; give way to those that are most compe-' tent. To use a familiar proverb, the weakest comes to the wall. But the triumphant fraction again breeds to overproduction, transmitting the qualities which secured its maintenance, but transmitting them in different degrees. The struggle for food again supervenes, and those to whom the favourable quality has been transmitted in excess will assuredly triumph. It is easy to see that we have here the addition of increments favourable to the individual still more rigorously carried out than in the case of domestication; for not only are unfavourable specimens not selected by nature, but they are destroyed. This is what Mr Darwin calls 'Natural Selection,' which ' acts by the preservation and accumulation of small inherited modifications, each, profitable to the preserved being.'. Witi this idea he interpenetrates and leavens the vast store of facts that he and others have collected. We cannot, without shutting our eyes through fear or prejudice, fan to see that Darwin ia here dealing, not with imaginary, but with true .causes ; nor can we fail to discern what vast modifications may be produced by natural selection in periods sufficiently long. Each individual increment may resemble what mathematicians call a ' differential * (a quantity indefinitely small); but definite and great changes | may obviously be produced by the integration of these infinitesimal quantities through practically infinite time.

(1) The first step only towards experimental demonstration has been taken. Experiments now begun might, a couple of centuries hence, furnish data of incalculable value, which ought to be supplied to the science of the future. I (To be continued)

S .'TJ^JR E S