Darwin and Modern Science Part 31

Except during the summer vacation, when he was visiting his father and uncle, and with the latter making his first observations upon the work of earthworms, Darwin was busy with his arrangements for the publication of the five volumes of the "Zoology of the 'Beagle'" and in getting the necessary financial aid from the government for the preparation of the plates. He was at the same time preparing his "Journal" for publication.

During the years 1837 to 1843, Darwin worked intermittently on the volumes of Zoology, all of which he edited, while he wrote introductions to those by Owen and Waterhouse and supplied notes to the others.

Although Darwin says of his Journal that the preparation of the book "was not hard work, as my MS. Journal had been written with care." Yet from the time that he settled at 36, Great Marlborough Street in March, 1837, to the following November he was occupied with this book. He tells us that the account of his scientific observations was added at this time. The work was not published till March, 1839, when it appeared as the third volume of the "Narrative of the Surveying Voyages of H.M.

s.h.i.+ps 'Adventure' and 'Beagle' between the years 1826 and 1836". The book was probably a long time in the press, for there are no less than 20 pages of addenda in small print. Even in this, its first form, the work is remarkable for its freshness and charm, and excited a great amount of attention and interest. In addition to matters treated of in greater detail in his other works, there are many geological notes of extreme value in this volume, such as his account of lightning tubes, of the organisms found in dust, and of the obsidian bombs of Australia.

Having thus got out of hand a number of preliminary duties, Darwin was ready to set to work upon the three volumes which were designed by him to const.i.tute "The Geology of the Voyage of the 'Beagle'". The first of these was to be on "The Structure and Distribution of Coral-reefs". He commenced the writing of the book on October 5, 1838, and the last proof was corrected on May 6, 1842. Allowing for the frequent interruptions through illness, Darwin estimated that it cost him twenty months of hard work.

Darwin has related how his theory of Coral-reefs which was begun in a more "deductive spirit" than any of his other work, for in 1834 or 1835 it "was thought out on the west coast of South America, before I had seen a true coral-reef." ("L.L." I. page 70.) The final chapter in Lyell's second volume of the "Principles" was devoted to the subject of Coral-reefs, and a theory was suggested to account for the peculiar phenomena of "atolls." Darwin at once saw the difficulty of accepting the view that the numerous and diverse atolls all represent submerged volcanic craters. His own work had for two years been devoted to the evidence of land movements over great areas in South America, and thus he was led to announce his theory of subsidence to account for barrier and encircling reefs as well as atolls.

Fortunately, during his voyage across the Pacific and Indian Oceans, in his visit to Australia and his twelve days' hard work at Keeling Island, he had opportunities for putting his theory to the test of observation.

On his return to England, Darwin appears to have been greatly surprised at the amount of interest that his new theory excited. Urged by Lyell, he read to the Geological Society a paper on the subject, as we have seen, with as little delay as possible, but this paper was "withdrawn by permission of the Council." An abstract of three pages however appeared in the "Proceedings of the Geological Society". (Vol. II. pages 552-554 (May 31, 1837).) A full account of the observations and the theory was given in the "Journal" (1839) in the 40 pages devoted to Keeling Island in particular and to Coral formations generally. ("Journal" (1st edition), pages 439-69.)

It will be readily understood what an amount of labour the book on Coral reefs cost Darwin when we reflect on the number of charts, sailing directions, narratives of voyages and other works which, with the friendly a.s.sistance of the authorities at the Admiralty, he had to consult before he could draw up his sketch of the nature and distribution of the reefs, and this was necessary before the theory, in all its important bearings, could be clearly enunciated. Very pleasing is it to read how Darwin, although arriving at a different conclusion to Lyell, shows, by quoting a very suggestive pa.s.sage in the "Principles"

(1st edition Vol. II. page 296.), how the latter only just missed the true solution. This pa.s.sage is cited, both in the "Journal" and the volume on Coral-reefs. Lyell, as we have seen, received the new theory not merely ungrudgingly, but with the utmost enthusiasm.

In 1849 Darwin was gratified by receiving the support of Dana, after his prolonged investigation in connection with the U.S. Exploring Expedition ("M.L." II. pages 226-8.), and in 1874 he prepared a second edition of his book, in which some objections which had been raised to the theory were answered. A third edition, edited by Professor Bonney, appeared in 1880, and a fourth (a reprint of the first edition, with introduction by myself) in 1890.

Although Professor Semper, in his account of the Pelew Islands, had suggested difficulties in the acceptance of Darwin's theory, it was not till after the return of the "Challenger" expedition in 1875 that a rival theory was propounded, and somewhat heated discussions were raised as to the respective merits of the two theories. While geologists have, nearly without exception, strongly supported Darwin's views, the notes of dissent have come almost entirely from zoologists. At the height of the controversy unfounded charges of unfairness were made against Darwin's supporters and the authorities of the Geological Society, but this unpleasant subject has been disposed of, once for all, by Huxley.

("Essays upon some Controverted Questions", London, 1892, pages 314-328 and 623-625.)

Darwin's final and very characteristic utterance on the coral-reef controversy is found in a letter which he wrote to Professor Alexander Aga.s.siz, May 5th, 1881: less than a year before his death: "If I am wrong, the sooner I am knocked on the head and annihilated so much the better. It still seems to me a marvellous thing that there should not have been much, and long-continued, subsidence in the beds of the great oceans. I wish that some doubly rich millionaire would take it into his head to have borings made in some of the Pacific and Indian atolls, and bring home cores for slicing from a depth of 500 or 600 feet." ("L.L."

III. page 184.)

Though the "doubly rich millionaire" has not been forthcoming, the energy, in England, of Professor Sollas, and in New South Wales of Professor Anderson Stuart served to set on foot a project, which, aided at first by the British a.s.sociation for the Advancement of Science, and afterwards taken up jointly by the Royal Society, the New South Wales Government, and the Admiralty, has led to the most definite and conclusive results.

The Committee appointed by the Royal Society to carry out the undertaking included representatives of all the views that had been put forward on the subject. The place for the experiment was, with the consent of every member of the Committee, selected by the late Admiral Sir W.J. Wharton--who was not himself an adherent of Darwin's views--and no one has ventured to suggest that his selection, the splendid atoll of Funafuti, was not a most judicious one.

By the pluck and perseverance of Professor Sollas in the preliminary expedition, and of Professor T. Edgeworth David and his pupils, in subsequent investigations of the island, the rather difficult piece of work was brought to a highly satisfactory conclusion. The New South Wales Government lent boring apparatus and workmen, and the Admiralty carried the expedition to its destination in a surveying s.h.i.+p which, under Captain (now Admiral) A. Mostyn Field, made the most complete survey of the atoll and its surrounding seas that has ever been undertaken in the case of a coral formation.

After some failures and many interruptions, the boring was carried to the depth of 1114 feet, and the cores obtained were sent to England.

Here the examination of the materials was fortunately undertaken by a zoologist of the highest repute, Dr G.J. Hinde--who has a wide experience in the study of organisms by sections--and he was aided at all points by specialists in the British Museum of Natural History and by other naturalists. Nor were the chemical and other problems neglected.

The verdict arrived at, after this most exhaustive study of a series of cores obtained from depths twice as great as that thought necessary by Darwin, was as follows:--"The whole of the cores are found to be built up of those organisms which are seen forming coral-reefs near the surface of the ocean--many of them evidently in situ; and not the slightest indication could be detected, by chemical or microscopic means, which suggested the proximity of non-calcareous rocks, even in the lowest portions brought up."

But this was not all. Professor David succeeded in obtaining the aid of a very skilful engineer from Australia, while the Admiralty allowed Commander F.C.D. St.u.r.dee to take a surveying s.h.i.+p into the lagoon for further investigations. By very ingenious methods, and with great perseverance, two borings were put down in the midst of the lagoon to the depth of nearly 200 feet. The bottom of the lagoon, at the depth of 101 1/2 feet from sea-level, was found to be covered with remains of the calcareous, green sea-weed Halimeda, mingled with many foraminifera; but at a depth of 163 feet from the surface of the lagoon the boring tools encountered great ma.s.ses of coral, which were proved from the fragments brought up to belong to species that live within AT MOST 120 feet from the surface of the ocean, as admitted by all zoologists. ("The Atoll of Funafuti; Report of the Coral Reef Committee of the Royal Society", London, 1904.)

Darwin's theory, as is well known, is based on the fact that the temperature of the ocean at any considerable depth does not permit of the existence and luxuriant growth of the organisms that form the reefs.

He himself estimated this limit of depth to be from 120 to 130 feet; Dana, as an extreme, 150 feet; while the recent very prolonged and successful investigations of Professor Alexander Aga.s.siz in the Pacific and Indian Oceans lead him also to a.s.sign a limiting depth of 150 feet; the EFFECTIVE, REEF-FORMING CORALS, however, flouris.h.i.+ng at a much smaller depth. Mr Stanley Gardiner gives for the most important reef-forming corals depths between 30 and 90 feet, while a few are found as low as 120 feet or even 180 feet.

It will thus be seen that the verdict of Funafuti is clearly and unmistakeably in favour of Darwin's theory. It is true that some zoologists find a difficulty in realising a slow sinking of parts of the ocean floor, and have suggested new and alternative explanations: but geologists generally, accepting the proofs of slow upheaval in some areas--as shown by the admirable researches of Alexander Aga.s.siz--consider that it is absolutely necessary to admit that this elevation is balanced by subsidence in other areas. If atolls and barrier-reefs did not exist we should indeed be at a great loss to frame a theory to account for their absence.

After finis.h.i.+ng his book on Coral-reefs, Darwin made his summer excursion to North Wales, and prepared his important memoir on the glaciers of that district: but by October (1842) we find him fairly settled at work upon the second volume of his "Geology of the 'Beagle'--Geological Observations on the Volcanic Islands, visited during the Voyage of H.M.S. 'Beagle'". The whole of the year 1843 was devoted to this work, but he tells his friend Fox that he could "manage only a couple of hours per day, and that not very regularly." ("L.L." I.

page 321.) Darwin's work on the various volcanic islands examined by him had given him the most intense pleasure, but the work of writing the book by the aid of his notes and specimens he found "uphill work," especially as he feared the book would not be read, "even by geologists." (Loc. cit.)

As a matter of fact the work is full of the most interesting observations and valuable suggestions, and the three editions (or reprints) which have appeared have proved a most valuable addition to geological literature. It is not necessary to refer to the novel and often very striking discoveries described in this well-known work. The subsidence beneath volcanic vents, the enormous denudation of volcanic cones reducing them to "basal wrecks," the effects of solfatarric action and the formation of various minerals in the cavities of rocks--all of these subjects find admirable ill.u.s.tration from his graphic descriptions. One of the most important discussions in this volume is that dealing with the "lamination" of lavas as especially well seen in the rocks of Ascension. Like Scrope, Darwin recognised the close a.n.a.logy between the structure of these rocks and those of metamorphic origin--a subject which he followed out in the volume "Geological Observations on South America".

Of course in these days, since the application of the microscope to the study of rocks in thin sections, Darwin's nomenclature and descriptions of the petrological characters of the lavas appear to us somewhat crude.

But it happened that the "Challenger" visited most of the volcanic islands described by Darwin, and the specimens brought home were examined by the eminent petrologist Professor Renard. Renard was so struck with the work done by Darwin, under disadvantageous conditions, that he undertook a translation of Darwin's work into French, and I cannot better indicate the manner in which the book is regarded by geologists than by quoting a pa.s.sage from Renard's preface. Referring to his own work in studying the rocks brought home by the "Challenger"

(Renard's descriptions of these rocks are contained in the "Challenger Reports". Mr Harker is supplementing these descriptions by a series of petrological memoirs on Darwin's specimens, the first of which appeared in the "Geological Magazine" for March, 1907.), he says:

"Je dus, en me livrant a ces recherches, suivre ligne par ligne les divers chapitres des "Observations geologiques" consacrees aux iles de l'Atlantique, oblige que j'etais de comparer d'une maniere suivie les resultats auxquels j'etais conduit avec ceux de Darwin, qui servaient de controle a mes constatations. Je ne tardai pas a eprouver une vive admiration pour ce chercheur qui, sans autre appareil que la loupe, sans autre reaction que quelques essais pyrognostiques, plus rarement quelques mesures au goniometre, parvenait a discerner la nature des agregats mineralogiques les plue complexes et les plus varies. Ce coup d'oeil qui savait embra.s.ser de si vastes horizons, penetre ici profondement tous les details lithologiques. Avec quelle surete et quelle exact.i.tude la structure et la composition des roches ne sont'elles pas determinees, l'origne de ces ma.s.ses minerales deduite et confirmee par l'etude comparee des manifestations volcaniques d'autres regions; avec quelle science les relations entre les faits qu'il decouvre et ceux signales ailleurs par ses devanciers ne sont'elles pas etablies, et comme voici ebranlees les hypotheses regnantes, admises sans preuves, celles, par exemple, des crateres de soulevement et de la differenciation radicale des phenomenes plutoniques et volcaniques!

Ce qui acheve de donner a ce livre un incomparable merite, ce sont les idees nouvelles qui s'y trouvent en germe et jetees la comme au hasard ainsi qu'un superflu d'abondance intellectuelle inepuisable."

("Observations Geologiques sur les Iles Volcaniques... ", Paris, 1902, pages vi., vii.)

While engaged in his study of banded lavas, Darwin was struck with the a.n.a.logy of their structure with that of glacier ice, and a note on the subject, in the form of a letter addressed to Professor J.D. Forbes, was published in the "Proceedings of the Royal Society of Edinburgh". (Vol.

II. (1844-5), pages 17, 18.)

From April, 1832, to September, 1835, Darwin had been occupied in examining the coast or making inland journeys in the interior of the South American continent. Thus while eighteen months were devoted, at the beginning and end of the voyage to the study of volcanic islands and coral-reefs, no less than three and a half years were given to South American geology. The heavy task of dealing with the notes and specimens acc.u.mulated during that long period was left by Darwin to the last.

Finis.h.i.+ng the "Volcanic Islands" on February 14th, 1844, he, in July of the same year, commenced the preparation of two important works which engaged him till near the end of the year 1846. The first was his "Geological Observations on South America", the second a recast of his "Journal", published under the short t.i.tle of "A Naturalist's Voyage round the World".

The first of these works contains an immense amount of information collected by the author under great difficulties and not unfrequently at considerable risk to life and health. No sooner had Darwin landed in South America than two sets of phenomena powerfully arrested his attention. The first of these was the occurrence of great ma.s.ses of red mud containing bones and sh.e.l.ls, which afforded striking evidence that the whole continent had shared in a series of slow and gradual but often interrupted movements. The second related to the great ma.s.ses of crystalline rocks which, underlying the muds, cover so great a part of the continent. Darwin, almost as soon as he landed, was struck by the circ.u.mstance that the direction, as shown by his compa.s.s, of the prominent features of these great crystalline rock-ma.s.ses--their cleavage, master-joints, foliation and pegmat.i.te veins--was the same as the orientation described by Humboldt (whose works he had so carefully studied) on the west of the same great continent.

The first five chapters of the book on South America were devoted to formations of recent date and to the evidence collected on the east and west coasts of the continent in regard to those grand earth-movements, some of which could be shown to have been accompanied by earthquake-shocks. The fossil bones, which had given him the first hint concerning the mutability of species, had by this time been studied and described by comparative anatomists, and Darwin was able to elaborate much more fully the important conclusion that the existing fauna of South America has a close a.n.a.logy with that of the period immediately preceding our own.

The remaining three chapters of the book dealt with the metamorphic and plutonic rocks, and in them Darwin announced his important conclusions concerning the relations of cleavage and foliation, and on the close a.n.a.logy of the latter structure with the banding found in rock-ma.s.ses of igneous origin. With respect to the first of these conclusions, he received the powerful support of Daniel Sharpe, who in the years 1852 and 1854 published two papers on the structure of the Scottish Highlands, supplying striking confirmation of the correctness of Darwin's views. Although Darwin's and Sharpe's conclusions were contested by Murchison and other geologists, they are now universally accepted. In his theory concerning the origin of foliation, Darwin had been to some extent antic.i.p.ated by Scrope, but he supplied many facts and ill.u.s.trations leading to the gradual acceptance of a doctrine which, when first enunciated, was treated with neglect, if not with contempt.

The whole of this volume on South American geology is crowded with the records of patient observations and suggestions of the greatest value; but, as Darwin himself saw, it was a book for the working geologist and "caviare to the general." Its author, indeed, frequently expressed his sense of the "dryness" of the book; he even says "I long hesitated whether I would publish it or not," and he wrote to Leonard Horner "I am astonished that you should have had the courage to go right through my book." ("M.L." II. page 221.)

Fortunately the second book, on which Darwin was engaged at this time, was of a very different character. His "Journal", almost as he had written it on board s.h.i.+p, with facts and observations fresh in his mind, had been published in 1839 and attracted much attention. In 1845, he says, "I took much pains in correcting a new edition," and the work which was commenced in April, 1845, was not finished till August of that year. The volume contains a history of the voyage with "a sketch of those observations in Natural History and Geology, which I think will possess some interest for the general reader." It is not necessary to speak of the merits of this scientific cla.s.sic. It became a great favourite with the general public--having pa.s.sed through many editions--it was, moreover, translated into a number of different languages. Darwin was much gratified by these evidences of popularity, and naively remarks in his "Autobiography", "The success of this my first literary child tickles my vanity more than that of any of my other books" ("L.L." I. page 80.)--and this was written after the "Origin of Species" had become famous!

In Darwin's letters there are many evidences that his labours during these ten years devoted to the working out of the geological results of the voyage often made many demands on his patience and indomitable courage. Most geologists have experience of the contrast between the pleasures felt when wielding the hammer in the field, and the duller labour of plying the pen in the study. But in Darwin's case, innumerable interruptions from sickness and other causes, and the oft-deferred hope of reaching the end of his task were not the only causes operating to make the work irksome. The great project, which was destined to become the crowning achievement of his life, was now gradually a.s.suming more definite shape, and absorbing more of his time and energies.

Nevertheless, during all this period, Darwin so far regarded his geological pursuits as his PROPER "work," that attention to other matters was always spoken of by him as "indulging in idleness." If at the end of this period the world had sustained the great misfortune of losing Darwin by death before the age of forty--and several times that event seemed only too probable--he might have been remembered only as a very able geologist of most advanced views, and a traveller who had written a scientific narrative of more than ordinary excellence!

The completion of the "Geology of the 'Beagle'" and the preparation of a revised narrative of the voyage mark the termination of that period of fifteen years of Darwin's life during which geological studies were his princ.i.p.al occupation. Henceforth, though his interest in geological questions remained ever keen, biological problems engaged more and more of his attention to the partial exclusion of geology.

The eight years from October, 1846, to October, 1854, were mainly devoted to the preparation of his two important monographs on the recent and fossil Cirripedia. Apart from the value of his description of the fossil forms, this work of Darwin's had an important influence on the progress of geological science. Up to that time a practice had prevailed for the student of a particular geological formation to take up the description of the plant and animal remains in it--often without having anything more than a rudimentary knowledge of the living forms corresponding to them. Darwin in his monograph gave a very admirable ill.u.s.tration of the enormous advantage to be gained--alike for biology and geology--by undertaking the study of the living and fossil forms of a natural group of organisms in connection with one another. Of the advantage of these eight years of work to Darwin himself, in preparing for the great task lying before him, Huxley has expressed a very strong opinion indeed. ("L.L." II. pages 247-48.)

But during these eight years of "species work," Darwin found opportunities for not a few excursions into the field of geology. He occasionally attended the Geological Society, and, as we have already seen, read several papers there during this period. His friend, Dr Hooker, then acting as botanist to the Geological Survey, was engaged in studying the Carboniferous flora, and many discussions on Palaezoic plants and on the origin of coal took place at this period. On this last subject he felt the deepest interest and told Hooker, "I shall never rest easy in Down churchyard without the problem be solved by some one before I die." ("M.L." I. pages 63, 64.)

As at all times, conversations and letters with Lyell on every branch of geological science continued with unabated vigour, and in spite of the absorbing character of the work on the Cirripedes, time was found for all. In 1849 his friend Herschel induced him to supply a chapter of forty pages on Geology to the Admiralty "Manual of Scientific Inquiry"

which he was editing. This is Darwin's single contribution to books of an "educational" kind. It is remarkable for its clearness and simplicity and attention to minute details. It may be read by the student of Darwin's life with much interest, for the directions he gives to an explorer are without doubt those which he, as a self-taught geologist, proved to be serviceable during his life on the "Beagle".

On the completion of the Cirripede volumes, in 1854, Darwin was able to grapple with the immense pile of MS. notes which he had acc.u.mulated on the species question. The first sketch of 35 pages (1842), had been enlarged in 1844 into one of 230 pages ([The first draft of the "Origin"

is being prepared for Press by Mr Francis Darwin and will be published by the Cambridge University Press this year (1909). A.C.S.]); but in 1856 was commenced the work (never to be completed) which was designed on a scale three or four times more extensive than that on which the "Origin of Species" was in the end written.

In drawing up those two masterly chapters of the "Origin", "On the Imperfection of the Geological Record," and "On the Geological Succession of Organic Beings", Darwin had need of all the experience and knowledge he had been gathering during thirty years, the first half of which had been almost wholly devoted to geological study. The most enlightened geologists of the day found much that was new, and still more that was startling from the manner of its presentation, in these wonderful essays. Of Darwin's own sense of the importance of the geological evidence in any presentation of his theory a striking proof will be found in a pa.s.sage of the touching letter to his wife, enjoining the publication of his sketch of 1844. "In case of my sudden death,"

he wrote, "... the editor must be a geologist as well as a naturalist."

("L.L." II. pages 16, 17.)

In spite of the numerous and valuable palaeontological discoveries made since the publication of "The Origin of Species", the importance of the first of these two geological chapters is as great as ever. It still remains true that "Those who believe that the geological record is in any degree perfect, will at once reject the theory"--as indeed they must reject any theory of evolution. The striking pa.s.sage with which Darwin concludes this chapter--in which he compares the record of the rocks to the much mutilated volumes of a human history--remains as apt an ill.u.s.tration as it did when first written.

And the second geological chapter, on the Succession of Organic Beings--though it has been strengthened in a thousand ways, by the discoveries concerning the pedigrees of the horse, the elephant and many other aberrant types, though new light has been thrown even on the origin of great groups like the mammals, and the gymnosperms, though not a few fresh links have been discovered in the chains of evidence, concerning the order of appearance of new forms of life--we would not wish to have re-written. Only the same line of argument could be adopted, though with innumerable fresh ill.u.s.trations. Those who reject the reasonings of this chapter, neither would they be persuaded if a long and complete succession of "ancestral forms" could rise from the dead and pa.s.s in procession before them.

Among the geological discussions, which so frequently occupied Darwin's attention during the later years of his life, there was one concerning which his att.i.tude seemed somewhat remarkable--I allude to his views on "the permanence of Continents and Ocean-basins." In a letter to Mr Mellard Reade, written at the end of 1880, he wrote: "On the whole, I lean to the side that the continents have since Cambrian times occupied approximately their present positions. But, as I have said, the question seems a difficult one, and the more it is discussed the better." ("M.L."

II. page 147.) Since this was written, the important contribution to the subject by the late Dr W.T. Blanford (himself, like Darwin, a naturalist and geologist) has appeared in an address to the Geological Society in 1890; and many discoveries, like that of Dr Woolnough in Fiji, have led to considerable qualifications of the generalisation that all the islands in the great ocean are wholly of volcanic or coral origin.