Charles Lyell and Modern Geology

CHAPTER V.

THE HISTORY AND PLACE IN SCIENCE OF THE "PRINCIPLES OF GEOLOGY."

The publication of the last volume of the "Principles of Geology" formed an important epoch in Lyell's life. It brought to a successful close a work on which his energies had been definitely concentrated for nearly five years, and for which he had been preparing himself during a considerably longer time. It placed him, before his fourth decade was completed, at once and beyond all question in the front rank of British geologists; it carried his reputation to every country where that science was cultivated. It proved the writer to be not only a careful observer and a reasoner of exceptional inductive power, but also a man of general culture and a master of his mother tongue. The book, moreover, marked an epoch in geology not less important; it produced an influence on the science greater and more permanent than any work which had been previously written, or has since appeared – greater even than the famous "Origin of Species by Natural Selection," for that dealt only with one portion of geology – viz. with palæontology, while the method of the Principles affected the science in every part. For a brief interval, then, we may desert the biography of the author for that of the book – the parent for his offspring – and call attention to one or two topics which are more immediately connected with the book itself. A brief sketch of its future history may be placed first; for, as its author was constantly labouring to improve and perfect his work, it underwent many changes in form and arrangement during the remainder – some two-and-forty years – of his life, which will be better understood from a connected statement than if they have to be gathered from scattered references in the other chapters of his biography.

The first volume of the "Principles of Geology" appeared, as has been mentioned, in January, 1830; the second in January, 1832; and the third in May, 1833. But a second edition of the first volume was issued in January, 1832, and one of the second volume in the same month of 1833; these were all in 8vo size. A new edition of the whole work was published in May, 1834. This, however, took the form of four volumes 12mo. This edition was called the third, because the first two volumes of the original work had gone through second editions. A fourth edition followed in June, 1835, and a fifth in March, 1837.

Thus far the "Principles" continued without any substantial alteration, but the author made an important change in preparing the next edition. He detached from it the latter part – practically, the matter comprised in the third volume of the original work. This he rewrote and published separately as a single volume in July, 1838, under the title of "Elements of Geology"; a sixth edition of the "Principles," thus curtailed, appeared in three volumes 12mo, in June, 1840. The effect of the change was to restrict the "Principles" mainly to the physical side of geology – to the subjects connected with the morphological changes which the earth and its inhabitants alike undergo. Thus it made the contents of the book accord more strictly with its title, while the "Elements" indicated the working out of the aforesaid principles in the past history of the earth and its inhabitants – that is, the latter book deals with the classification of rocks and fossils, or with petrology and historical geology. The subsequent history of the "Elements" may be left for the present.

In February, 1847, the seventh edition of the "Principles" appeared, in which another change was made. This, however, was in form rather than in substance, for the book was now issued in a single thick 8vo volume. The eighth edition, published in May, 1850; and the ninth, in June, 1853, followed the same pattern. A longer interval elapsed before the appearance of the tenth edition, and this was published in two volumes, the first being issued in November, 1866, and the second in 1868. In this interval – more than thirteen years – the science had made rapid progress, and the process of revision had been in consequence more than usually searching. The author, as he states in the preface, had "found it necessary entirely to rewrite some chapters, and recast others, and to modify or omit some passages given in former editions." Many new instances were given to illustrate the effect which forces still at work had produced upon the earth's crust, and these strengthened the evidence which had been already advanced. Into the accounts of Vesuvius and Etna much important matter was introduced, the result of visits which, as we shall find, Lyell made in 1857 and 1858; the chapters relating to the vicissitudes of climate in past geological ages were entirely rewritten, together with that discussing the connection between climate and the geography of the earth's surface; and a chapter, practically new, was inserted, which considered "how far former vicissitudes in climate may have been influenced by astronomical changes; such as variations in the eccentricity of the earth's orbit, changes in the obliquity of the ecliptic, and different phases of the precession of the equinoxes." But the most important change was made in the later part of the book – the last fifteen chapters.55 These either were entirely new, or presented the original material in a new aspect. In the earlier editions of his work, Lyell had expressed himself dissatisfied, as we have already seen, with the idea of the derivation of species from antecedent forms by some process of modification, and had pointed out the weak places in the arguments which were advanced in its favour. But the evidence adduced by Darwin and Wallace in regard to the origin of species by natural selection, strengthened by the support of Hooker on the botanical side, had removed the difficulties which the cruder statements of Lamarck and other predecessors had suggested to his mind, so that Lyell now appears as a convinced evolutionist. The question also of the antiquity of man is much more fully discussed than it had been in the earlier editions.

Considerable changes were introduced into the eleventh edition, which appeared in January, 1872, but these were chiefly additions which were made possible by the rapidly increasing store of knowledge, as, for instance, much important information concerning the deeper parts of the ocean. On this interesting subject great light had been thrown by the cruises of the several exploring vessels, notably those of the Lightning, the Bulldog, and the Porcupine, commissioned by the British Government – cruises in the course of which soundings had been taken and temperatures observed in the North Atlantic down to depths of about 2,500 fathoms; and in the lowest parts of the western basin of the Mediterranean. Samples also of the bottom had been obtained, and, in many cases, even dredgers had been successfully employed at these depths. Thanks to the skill of the mechanician, the way had been opened which led into a new fairyland of science. This was not, like some fabled Paradise, guarded by mountain fastnesses and precipitous ramparts of eternal snow; it was not encircled by storm-swept deserts, or secluded in the furthest recesses of forests, hitherto impenetrable; but it lay deep in the silent abysses of ocean – on those vast plains, which are unruffled by the most furious gale, or by the wildest waves. In these depths, beneath the tremendous pressure of so vast a thickness of water, and far below the limits at which the existence of life had been supposed to be possible, numbers of creatures had been discovered – many of them strange and novel: molluscs, sea-lilies, glassy sponges of unusual beauty – creatures often of ancient aspect, relics of a fauna elsewhere extinct; and the ocean floor, on and above which they moved, was strewn with the white dust of countless coverings of tiny foraminifera, which, even if none were actually living, had fallen like a gentle but incessant rain from the overhanging mass of water.

Similar changes were introduced into the twelfth edition of the "Principles," upon which the author was engaged even up to the last few weeks of his life. The Challenger, it will be remembered, started on her memorable voyage of exploration at the close of the year in which the eleventh edition had appeared; and though she did not actually return till after Lyell's death, notes of some of her most interesting discoveries had been communicated from time to time to the scientific journals of this country. The edition, however, was left incomplete. The first volume had been passed for the press, but the second was still unfinished; so that this twelfth edition was posthumous, the work of revision having been finished by the author's nephew and heir, Mr. Leonard Lyell.

By such conscientious and unremitting labour, the scientific value of the "Principles" was immensely increased; it kept always in step with the advance of the science, but at the same time it lost, as was inevitable, a little of that literary charm and that sense of freshness which was at first so marked a characteristic. Books, like children, are apt to lose some of their beauty as they increase in size and strength. One must compare an early and a late edition, such as the first or third and the tenth or eleventh, in order to realise how great were the changes in this passage from childhood to adolescence. New material was incorporated into every part; it makes its appearance sometimes on every page; changes are made in the order of the subjects; many chapters are entirely rewritten; nevertheless, a considerable portion corresponds almost word for word in the two editions. Lyell was no hurried writer, or "scamper" of work; he paid great attention to composition, so that when the facts which he desired to cite had undergone no change, he very seldom found any to make in his language. Nevertheless, here and there, some small modification, a slight verbal difference, a trifling alteration in the order of a sentence, the insertion of a short clause to secure greater perspicuity, shows to how careful and close a revision the whole had been subjected. In the substance of the work, besides the excision of nearly one-third of the material and the complete reconstruction of the part relating to the antiquity of man and the origin of species, already mentioned, the following are the most important changes. The chapters which discuss the evidence in favour of past mutations of climate and the causes to which these are due, are rewritten and greatly enlarged. In the earlier editions, the effects of geographical changes were regarded as sufficient to account for all the climatal variations that geology requires; in the later editions, the possible co-operation of astronomical changes is admitted. Great additions also are made to the parts referring to the condition of the bed of the ocean, and much new and important information is incorporated into the sections dealing with volcanoes and earthquakes; including many valuable observations which had been made during visits to Vesuvius and to Etna in the autumns of 1857 and 1858. The section on the action of ice is so altered and enlarged as to be practically new; for when the first edition of the "Principles" was published comparatively little was known of the effects of land-ice, and the art of following the trail of vanished glaciers had yet to be learnt. But, with this exception, the part of the book dealing with the action of the forces of Nature – heat and cold, rain, rivers, and sea – remains comparatively unaltered, as do the first five chapters, which give a sketch of the early history of the science of geology.

Without some knowledge of this history it is hardly possible to appreciate the true greatness of the "Principles," and its unique value as an influence on scientific thought at the time it appeared. This, however, to some extent may be inferred from those chapters which we have mentioned; but the perspective of half a century enables us to understand it better at the present time; for the author, of course, had to deal with contemporary work and opinion only in a very indirect way. We may dismiss briefly the crude speculations of the earliest observers – those anterior to the Christian era – of which the author gives a summary in the second chapter of the "Principles"; for at that early date few persons had made any effort to arrange the facts of Nature in a connected system. These were too scanty and too disconnected for any such effort to be successful. The general result cannot be better summed up than in Lyell's own words: —

"Although no particular investigations had been made for the express purpose of interpreting the monuments of ancient changes, they were too obvious to be entirely disregarded; and the observation of the present course of Nature presented too many proofs of alterations continually in progress on the earth to allow philosophers to believe that Nature was in a state of rest, or that the surface had remained and would continue to remain, unaltered. But they had never compared attentively the results of the destroying and the reproductive operations of modern times with those of remote eras; nor had they ever entertained so much as a conjecture concerning the comparative antiquity of the human race, or of living species of animals and plants, with those belonging to former conditions of the organic world. They had studied the movements and positions of the heavenly bodies with laborious industry, and made some progress in investigating the animal, vegetable, and mineral kingdoms; but the ancient history of the globe was to them a sealed book, and though written in characters of the most striking and imposing kind, they were unconscious even of its existence."56

The above remarks hold good for the centuries immediately succeeding the Christian era; and the influence of the new faith, when it ceased to be persecuted and became a power in the state, was adverse on the whole to progress in physical or natural science. With the decline of the Roman empire a great darkness fell upon the civilised world; art, science, literature withered before the hot breath of war and rapine, as the northern barbarians swept down upon their enfeebled master on their errand of destruction. It was well nigh eight centuries from the Christian era before the spirit of scientific enquiry and the love of literature began to awaken from their long torpor; and it was then among people of an Eastern race and an alien creed. The caliphs of Bagdad encouraged learning, and the students of the East became familiar by means of translations with the thoughts and questionings of ancient Greece and Rome. The efforts of their earliest investigators have not been preserved, but in treatises of the tenth century – written by one Avicenna, a court physician, the "Formation and Classification of Minerals" is discussed, as well as the "Cause of Mountains." In the latter attention is called to the effect of earthquakes, and to the excavatory action of streams. In the same century also, "Omar the Learned" wrote a book on "the retreat of the sea," in which he proved by reference to ancient charts and by other less direct arguments that changes of importance had occurred in the form of the coast of Asia. But even among the followers of Mohammed theology declared itself hostile to science; the Moslem doctors of divinity deemed the pages of the Koran, not the book of Nature, man's proper sphere of research, and considered these difficulties ought to be settled by a quotation from the one rather than by facts from the other. So progress in science was impeded, and recantations at the bidding of ecclesiastics are not restricted to the annals of Christian races. But men seem to have gone on speculating, and Mohammed Kazwini, in a striking allegory which is quoted by Lyell, tells his readers how (to use the words of Tennyson)57: —

In Europe geological phenomena do not appear to have attracted serious attention till the sixteenth century, when the significance of fossils became the subject of an animated controversy in Italy. At that epoch this country held the front rank in learning and the arts, and an inquiry of that nature arose almost as a matter of course, because the marls, sands, and soft limestones of its lower districts teem in many places with shells and other marine organisms in a singular state of perfection and preservation. It is interesting to remark, that among the foremost in appealing to inductive processes for the explanation of these enigmas was that extraordinary and almost universal genius, Leonardo da Vinci. He ridiculed the current idea that these shells were formed "by the influence of the stars," calling attention to the mud by which they were filled, and the gravel beds among which they were intercalated, as proof that they had once lain upon the bed of the sea at no great distance from the coast. His induction rested on the evidence of sections which had been exposed during his construction of certain navigable canals in the north of Italy. Shortly afterward, the conclusions of Leonardo were amplified, and strengthened on similar grounds by Frascatoro. He, however, not only demonstrated the absurdity of explaining these organic structures by the "plastic force of Nature" – a favourite refuge for the intellectually destitute of that and even a later age, but he also showed that they could not even be relics of the Noachian deluge. "That inundation, he observed, was too transient; it had consisted principally of fluviatile waters; and if it had transported shells to great distances, must have strewed them over the surface, not buried them at vast depths in the interior of mountains." As Lyell truly remarks, "His clear exposition of the evidence would have terminated the discussion for ever, if the passions of man had not been enlisted in the dispute; and even though doubts should for a time have remained in some minds, they would speedily have been removed by the fresh information obtained almost immediately afterwards, respecting the structure of fossil remains, and of their living analogues." But the difficulties raised by theologians, and the general preference for deductive over inductive reasoning, greatly impeded progress. It was not till the methods of the schoolmen yielded place to those of the natural philosophers that the tide of battle began to turn, and science to possess the domains from which she had been unjustly excluded. For about a century the weary war went on; the philosophers of Italy leading the van, those of England, it must be admitted, for long lagging behind them, before the spectre of "plastic force" was finally dismissed to the limbo of exploded hypotheses in England. For instance, it was seriously maintained by the well-known writer on county history, Dr. Plot, in the last quarter of the seventeenth century, though its absurdity had been demonstrated by his Italian contemporaries; as by Scilla, in his treatise on the fossils of Calabria, and by Steno, in that on "Gems, crystals, and organic petrifactions enclosed in solid rocks." The latter had proved by dissecting a shark recently captured in the Mediterranean, that its teeth and bones corresponded exactly with similar objects from a fossil in Tuscany, and that the shells discovered in sundry Italian strata were identical with living species, except for the loss of their animal gluten and some slight mineral change. Moreover, he had distinguished, by means of their organic remains, between deposits of a marine and of a fluviatile character.

But now, as the "plastic force" dogma lost its hold on the minds of men, its place was taken by that which regarded all fossils as the relics of an universal deluge.

"The theologians who now entered the field in Italy, Germany, France, and England, were innumerable; and henceforward, they who refused to subscribe to the position that all marine organic remains were proofs of the Mosaic deluge, were exposed to the imputation of disbelieving the whole of the sacred writings. Scarce any step had been made in approximating to sound theories since the time of Frascatoro, more than a hundred years having been lost in writing down the dogma that organised fossils were mere sports of Nature. An additional period of a century and a half was now destined to be consumed in exploding the hypothesis that organised fossils had all been buried in the solid strata by Noah's flood."58

Into the varying fortunes of this second struggle it is needless to enter at any length. It was the old conflict between theology and science in a yet more acute form; the old warfare between deductive and inductive reasoning; between dogmatic ignorance and an honest search for truth. Protestants and Romanists alike seemed to claim the gift of infallibility, with the right to decide ex cathedrâ on questions of which they were profoundly ignorant, and to pronounce sentence in causes where they could not even appreciate the evidence. Ecclesiastics scolded; well-meaning though incompetent laymen echoed their cry; the more timorous among scientific men wasted their time in devising elaborate but futile schemes of accommodation between the discoveries of geology and the supposed revelations of the Scriptures; the stronger laboured on patiently, gathering evidence, strengthening their arguments and dissecting the fallacies by which they were assailed, until the popular prejudice should be allayed and men be calm enough to listen to the voice of truth. It was a long and weary struggle, which is now nearly, though not quite, ended; for there are still a few who mistake for an impregnable rock that which is merely the shifting-sand of popular opinion, and cannot realise that the province of revelation is in the spiritual rather than in the material, in the moral rather than in the scientific order. The outbursts of denunciation aroused by the assertion of the antiquity of man and the publication of the "Origin of Species," which many still in the full vigour of their powers can well remember, were but a recrudescence of the same spirit, a reappearance of an old foe with a new face.