THE LIBRARY 
 
 OF 
 
 THE UNIVERSITY 
 OF CALIFORNIA 
 
 PRESENTED BY 
 
 PROF. CHARLES A. KOFOID AND 
 MRS. PRUDENCE W. KOFOID 
 
 EARTH 
 
 SCIENCES 
 
 LIBRARY 
 
GEOLOGY: 
 
 ITS PAST AND PRESENT. 
 
 A LECTURE 
 
 DELIVERED TO THE MEMBERS OF THE GLASGOW ATHEXJ1UM, 
 JANUARY 13, 1859. 
 
 BY 
 
 THE DUKE OF ARGYLL. 
 
 RICHARD GRIFFIN AND CO. 
 
 GLASGOW AND LONDON. 
 
 MDCCCLIX. 
 
TAe Directors of the Glasgow Athenaeum have much pleasure in 
 acknowledging their obligations to His Grace the DUKE OF ARGYLL, 
 not only for having delivered the following Lecture to the Members, 
 but also for having genet^ously presented the Copyright to the 
 Institution. 
 
KAftTH 
 
 SCIENCES 
 
 UBRARY 
 
 GEOLOGY: ITS PAST AND PRESENT. 
 
 I HAVE been long under promise to the Directors of this 
 .Institution, to contribute to its Course of Lectures ; and 
 it has been suggested to me that a more full account of 
 some fossil remains which I had occasion to describe some 
 years ago to the British Association, might afford a sub- 
 ject of some popular interest. I propose, however, in this 
 Lecture to make the description of local facts subordinate 
 to some remarks on the science of Geology in general 
 on its past history and its future prospects on the main 
 conclusions which have been firmly established and on 
 some of those which are now the principal subjects of 
 discussion and of controversy. 
 
 The history of Geology is a very short one ; for of all 
 the sciences it is the youngest. Speculations, indeed, on 
 the structure of the earth, and on the history of its 
 creation, are old enough. Almost all mythologies con- 
 tain them ; and in all ages they have been a principal 
 ingredient in what was called Philosophy. But specu- 
 lation is not knowledge ; still less is it that systematic 
 knowledge which alone we dignify by the name of 
 Science. By Science we mean not Theories, not even 
 mere acquaintance with individual facts, but that kind 
 of acquaintance with them which consists in a knowledge 
 
 M3724K1 
 
of their relation to each other, and of the rule or law 
 under which their occurrence is determined. Now, it is 
 this kind of knowledge in respect to Geology which is of 
 such recent origin. There are probably some individuals 
 in this assembly of whom it may with truth be said, that 
 their early years date from a period before the science of 
 Geology was born. It was only in the beginning of the 
 present century that the foundation-stone of Geology, as a 
 science properly so called, was laid in the discovery and 
 establishment of this cardinal fact, that successive periods 
 in the history of the earth have been characterised by 
 successive varieties of animal and vegetable life ; that the 
 remains of these have been preserved in the rocks which 
 during those periods were in process of formation ; and 
 that by such remains the relative order of those rocks, 
 and their relative age, can be determined. 
 
 It may well seem strange that in Astronomy a science 
 which deals with bodies so immensely distant from us, that 
 most of them are seen only as specks of light by far the 
 most important part of all that we now know, was known 
 more than a century and a half ago ; whereas it is only, 
 as it were, in the present day that we have come to ascer- 
 tain the most elementary truths in respect to the history 
 and structure of our own planet. There are, however, 
 considerations which may account for this difference be- 
 tween the two departments of knowledge. It has arisen 
 partly from the difference of inducement to inquire into 
 the one, as compared with the inducement to inquire into 
 the other ; and partly to the difference in the methods 
 of investigation which the two sciences severally require. 
 As regards inducement : Objects distant and obscure ex- 
 cite our wonder far more than objects near and familiar ; 
 and wonder is the mother of all inquiry. So also, objects 
 which are in motion, all the more if the cause of that 
 motion be invisible, will at once arrest the attention, 
 
when objects which are still, however curious in them- 
 selves, will fail to do so. The very distance of the 
 heavenly bodies the very mystery of their movements, 
 together with the splendour of their appearance have 
 from the earliest ages attracted the wonder and ad- 
 miration of mankind. Nowhere have they more natu- 
 rally done so than in those countries whose inhabit- 
 ants were the earliest cultivators of Astronomy where 
 there is so little to distract the eye from the majesty 
 of the heavens, and where the purity of the atmos- 
 phere reveals their wonderful phenomena with a bril- 
 liancy unknown to us. But the rocks and stones of 
 the earth things which we are daily handling, or on 
 which we are daily treading what is there in these to 
 rouse curiosity or excite inquiry 1 To find out their phy- 
 sical properties, with a view to human use, might well 
 seem the farthest aim of knowledge in respect to them. 
 They were just what they had been made when the 
 earth itself was formed, and to seek their origin or his- 
 tory might seem like seeking the history of Creation 
 a search which could only lose itself in misty specula- 
 tions on the origin of matter. 
 
 No wonder, then, if Astronomy had the start of 
 Geology, on account simply of its more conspicuous 
 claim on the curiosity of mankind. Nor is it surprising 
 that, when inquiry had begun, it should have resulted 
 comparatively soon in the discovery of truths beyond 
 which there is even now hardly a glimmering of any 
 farther light. Astronomy is what is called an "exact 
 science." The methods and the instruments of inquiry 
 are alike peculiar. It is reasoning in its purest, severest, 
 most abstract form requiring, indeed, the highest powers 
 of mind for guidance and direction, but leading those who 
 are able to follow, to conclusions of absolute certainty, 
 and, so to speak, of mechanical precision. It is very 
 
different with Geology. Its conclusions are built up 
 from little gatherings on every side upon probabilities 
 and analogies upon indirect and circumstantial evidence. 
 The proof is not on this account the less perfect ; only 
 it is proof of another kind, requiring time, and the labour 
 of many observers to collect and digest the evidence. 
 
 And then some of those conclusions which we meet 
 with almost on the threshold of geology are very dif- 
 ficult of belief. Take the very first. There is no habit 
 of thought more born with us than that which leads us 
 to place confidence in the stability of the great elements 
 of Nature ; and especially on that relative distribution of 
 sea and land, by which alone we recognise our home, our 
 country, our very world itself. King David speaks of 
 the " everlasting hills ;" and such, indeed, they are not 
 merely in respect to the life of individual men, but in 
 respect also of the life of all human generations. Small 
 changes are perceptible in the course of centuries ; and 
 these may modify, perhaps considerably, the superficial 
 aspect of a country. But we are accustomed to think, 
 and to take pleasure in the thought, that all great natu- 
 ral features remain substantially unchanged. It is in 
 this confidence that we visit the scenes of great events, 
 and trace the outlines which were familiar to famous men. 
 The very first conclusion to which we are led in geolo- 
 gical science, is one which demands the surrender of all 
 these notions of the stability of the land, and of the bounds 
 within which the sea is stayed. It is no longer the " ever- 
 lasting hills" it is only the everlasting sea. We are 
 called upon to believe, not merely that here and there the 
 sea has gained upon the land, or the land has gained upon 
 the sea not merely that at some given time the waters 
 have covered the earth in sudden deluge, speedily retreat- 
 ing to their own bed again but that in the long history 
 of the globe, sea and land have been perpetually changing 
 
place not suddenly, or, as it were, by accident, but fre- 
 quently, almost regularly as an ordinary operation of 
 nature, and with intervals of rest as long and as peaceful 
 as that which has now lasted since man was born. 
 
 So hard of belief was this conclusion, that, although the 
 constant occurrence of sea-shells imbedded in the rocks was 
 one of the earliest circumstances which roused curiosity and 
 excited to inquiry, men would not, and apparently could 
 not, grasp the vast idea. A curious example of the almost 
 insuperable difficulty it presented, is to be found in a 
 work, not much read now, by no less celebrated an author 
 than Oliver Goldsmith. Among his many other literary 
 labours and incited, as he tells us, by admiration of the 
 writings of Pliny Goldsmith published in 1774 a treatise 
 on Natural History, which, though not a work of original 
 research, represents at least the condition of knowledge 
 in his day. The universal diffusion of marine shells had 
 attracted the notice of the ancients ; and some of them 
 appear to have drawn from this fact, conclusions which 
 were inadequate indeed, but which made some approxi- 
 mation to the truth. Many, however, of the earliest 
 modern inquirers had attributed the fact to the effects 
 of the Deluge. Then, when on farther consideration it 
 had become clear that no merely superficial or transitory 
 occupation by the sea could have deposited its produc- 
 tions deep in the bowels of the earth, incorporating them 
 with the very substance of the rocks in which they 
 are found, men were stupid enough to maintain that 
 fossils were mere sports of Nature things which had 
 never really been possessed of life, although made in 
 deceptive imitations of its forms. So grotesque a theory 
 could not long stand investigation ; and in the last century 
 a number of writers had vindicated for natural evidence 
 that confidence in its truthfulness, without which there 
 can be no progress in knowledge. Many of these argu- 
 
ments, and of the facts which had been collected in 
 support of them, were summed up in the work of the 
 great French naturalist Buffon which appeared in 1749. 
 Goldsmith professes himself entirely satisfied that the 
 shells found fossilised in the earth are really what they 
 appear to be the shells of molluscous animals which had 
 lived in water. He admits also that they appear for the 
 most part to be of kinds which live only in the sea ; but 
 so difficult of belief does he find the conclusions which 
 would seem to follow respecting the universal and con- 
 tinuous dominion of the ocean, that, in .the choice of 
 difficulties, he prefers the supposition that the shells 
 which appear to have been marine may really have been 
 only the produce of fresh-water lakes. Now, there are 
 fossils which really have been left by lakes ; but then 
 they are at once distinguishable as such, by precisely 
 analogous features to those by which we identify fresh- 
 water shells at the present day. The characteristic dis- 
 tinctions between the productions of the sea and those 
 of lakes, are just as certain and as constant as those 
 which distinguish both from the productions of the land ; 
 and any theory which refuses to recognise this distinc- 
 tion, when it is apparent, is just as much a denial of the 
 truthfulness of natural evidence, as that other theory 
 which considered all fossils as jests of Nature. Goldsmith 
 felt the difficulty, and only accepted it to escape from 
 what he considered the still greater difficulty of suppos- 
 ing that the solid land the great continents and highest 
 mountains of the earth had all at one time or another 
 been covered by the sea. 
 
 And it is well worthy of remark, that when men did 
 begin to accept this idea, they accepted it under condi- 
 tions very different from those which, as we now know, 
 had really prevailed. Our ideas of the processes of cre- 
 ation naturally take their form from our own human 
 
methods of manufacture or design. We do not readily 
 apprehend how slow and gradual are the growths of 
 nature, and how their perfection and variety are the 
 " long results of time." So, when the agency of the sea 
 came at last to be recognised in the structure of the 
 rocks, men imagined a sea very different from that of 
 which we have any knowledge some universal ocean, 
 whose waters held all the materials of the earth in suspen- 
 sion which had next let them fall, and then by its tides 
 and currents had heaped them into mountains or scooped 
 them into valleys. No wonder that Goldsmith, in re- 
 viewing these theories, speaks with some contempt of 
 human ingenuity when engaged in what he calls the 
 " amusement of earthmaking," and wishes that naturalists 
 would " be content with giving us facts instead of sys- 
 tems." Facts, however, are never so eagerly hunted out 
 as when the search is undertaken in defence of some 
 favourite theory ; nor is the bearing of facts ever so 
 well sifted as when some assumed interpretation is can- 
 vassed or denied. Goldsmith himself, in objecting to the 
 theory of a universal ocean, refers to one fact of which 
 due notice had not been taken. The very same rocks 
 which testified to the dominion of the sea, testified very 
 often quite as distinctly to the existence of dry land ; 
 for fossil-wood was as common as fossil-shells, and not 
 unfrequently the wood seemed older than the shells, 
 for it was lying underneath. However long, therefore, 
 the sea may have rested on the land, said Goldsmith, it 
 was clear that it could not have been either permanent 
 or universal ; and that, before the deposition of these 
 rocks, the earth must have been covered with trees, and 
 therefore " habitable, if not inhabited." 
 
 Goldsmith was not far wrong here. Geology gives us 
 no certain evidence of any time when the whole globe was 
 covered by the sea of any time when there was no dry 
 
8 
 
 land ; whilst the existence of fossil-wood and trees and 
 leaves in innumerable strata, proves, beyond the possibil- 
 ity of doubt, that the sea which deposited them was a sea 
 with shores, and those shores covered, as such shores now 
 are, with a terrestrial vegetation. "Where, then, was Gold- 
 smith's error I what was it that puzzled him so much ? 
 The sources of his difficulty may all be traced in one 
 word. He says that fossil- woods prove the Earth to have 
 been covered with trees. " The Earth : " yes ; but what 
 Earth 1 Not the Earth which we now see in familiar out- 
 lines on the terrestrial globe ; not Europe, Asia, Africa, 
 or America ; but some ancient Earth, whose continents 
 lay perhaps where the Atlantic lies now, and whose seas 
 rolled over the area now roughened by the Andes or the 
 Alps. The solution of the problem which presented 
 itself to his mind is not quite so difficult as he supposed. 
 He was not called upon to believe, as he thought he was, 
 that the " sea had for a long time covered the tops of the 
 highest mountains." No wonder he resisted this conclu- 
 sion as inconceivable. So it is. But what he was really 
 called upon to believe is very different. It is merely 
 this : That the mountains of .our earth, as they now exist, 
 are, like other things, the birth of time ; that there was 
 a period, or more periods than one, when the materials 
 of which they are composed had not been raised into the 
 form of mountains had not even been hardened into the 
 consistency of rocks, but lay accumulating, as sand or 
 silt or clay, in the bottom of primeval seas. 
 
 In order, however, to conceive this, it was necessary to 
 have an idea of some other agency than water for the 
 raising or upheaving of the land. The horizontal, or 
 nearly horizontal, position in which water tends to de- 
 posit its materials, could never be reconciled with the 
 broken, twisted, or contorted form which the consolidated 
 strata so frequently assume on land ; and every attempt 
 
to account for such appearances by the action of mere 
 tides and currents of the sea, were obviously futile. 
 The sea had quite enough work assigned to it in accu- 
 mulating the materials of the rocks, without throwing 
 on it the additional duty of raising them out of its own 
 bed, and heaping them into mountains. At last, and not 
 very long after Goldsmith wrote, an eminent countryman 
 of our own, Dr Hut-ton, made the requisite advance. Col- 
 lecting all that was best established in the facts and 
 reasonings of previous inquirers, and adding to them a 
 large store of original observation, he made a very near 
 approach to solving the most important mechanical pro- 
 blem in Geology. In proving that a large class of rocks 
 were the direct product, not of water, but of fire, whilst 
 the existing mineral condition of others was due in great 
 measure to the same agency fire breaking out in volca- 
 noes, or pent up under subterranean pressure he brought 
 prominently into view that tremendous and mysterious 
 force which from age to age has rent and upheaved the 
 land, and in various quarters of the globe is still causing 
 it to quake and tremble. Water, to grind down the 
 materials of the strata from the ruins of still older rocks ; 
 heat and pressure, to consolidate the materials ; and 
 subterranean or volcanic fire, to heave and break them up : 
 these again to be re-ground, re-stratified, re-consolidated, 
 re-elevated and so on, for ever ; "eternal process moving 
 on " through the same repeated cycle ; new worlds being 
 ever and again prepared from the waste and ruins of the 
 old ; such was the theory of Hutton ; a great advance 
 on former systems, inasmuch as it rested entirely upon 
 the operation of ordinary causes that is to say, causes 
 similar at least in kind to those which may be seen in 
 continuous or occasional operation now. It was the first 
 " Theory of the Earth " which contained something like 
 an adequate idea of the incalculable ages of geological 
 
10 
 
 time. According to this theory, there was in the consti- 
 tution of the globe " a power for interchanging sea and 
 land/' the constant operation of which through unnum- 
 bered ages would account for an}/ variety and extent of 
 change. It was in announcing this theory that Dr Hut- 
 ton expressed himself in the famous sentence the truth of 
 which is even now a matter of discussion, and the discus- 
 sion of which introduces us at once into the profound- 
 est questions with which human science can be called 
 to deal. Hutton denied that there were any rocks which 
 could be called " primitive," if by this were meant rocks 
 whose structure and composition could not be traced 
 to the same origin as the rest. There were, indeed, strata 
 which, being older than others, had been subject longer, and 
 more frequently, to the agencies of change. But there 
 were none which did not indicate the same ultimate origin 
 none which did not speak of a world still antecedent 
 to themselves, from whose ruins their materials had been 
 derived. There was, therefore, in Geology " no vestige of 
 a beginning no prospect of an end." 
 
 But during the same years that Hutton had been de- 
 voting himself to the proof, and maturing of his Theory 
 of the Earth, William Smith, an English land-surveyor, 
 of very humble scientific pretensions, was working his 
 way to the establishment of one great fact, which opened 
 up an entirely new prospect to geological science, and is 
 the foundation of all its subsequent marvellous progress. 
 That fact is this : that strata of contemporary formation 
 can always be identified by their imbedded fossils, inas- 
 much as the shells and animals contained in each stratum 
 are more or less exclusively peculiar to itself. His first 
 map of the English strata, arranged on this principle, was 
 published in 1799. By carefully following up the clue 
 which this principle affords/ and by means of analysis 
 more and more refined, applied to the structure of extinct 
 
11 
 
 forms of life, the science of Geology has now attained 
 results with which, in respect to their grandeur, and the 
 food they supply for thought, few other sciences can 
 compare. 
 
 The essential value of this discovery was the clue which 
 it afforded for the arrangement or classification of the 
 strata in the order of time. Dr Hutton had clearly seen 
 that the earth which we now inhabit, with its familiar 
 divisions of sea and land, was but one of the thousand 
 aspects which had been given to the globe in the course 
 of time past, and that some aspect wholly different would 
 result, in time still future, from forces which had been 
 ever working, and were working still. To his eye it was 
 an orderly procession of habitable worlds, in which, strain 
 our vision as we might, no point of departure could be seen. 
 But he had no suspicion of the fact, that the foot-prints 
 which these worlds had left upon the " Sands of Time," 
 contained within themselves a record of their place and 
 order in the march of worlds, and perhaps, too, an indi- 
 cation of progress from a definite beginning, towards a 
 definite result. Yet it is curious how narrowly he and 
 others had escaped this great discovery. He knew, and he 
 dwelt upon the fact, that successive worlds had left records 
 of their existence in the remains of their animals and their 
 plants. He knew, too, that those plants and animals could 
 not always be identified with those which are existing now. 
 But he passes lightly over this last fact, with the casual 
 observation, that such differences as existed were no 
 greater in kind or in degree than the differences which 
 are found now between contemporary species in the living 
 world. How often do we see, in the history of science, 
 men having, as it were, their very hand on treasures 
 which it was reserved for some happier successor to re- 
 cognise and secure ! Little did Hutton imagine that, by 
 measuring this difference of which he spoke so lightly, 
 
12 
 
 between the plants and animals of the present world, and 
 those which were fossilised in the various strata of the 
 earth, we have the means of arranging all past worlds in 
 the order of their birth a sounding-line by which to 
 measure the abysses of past time ; nay, more, a ray of 
 light cast upon that darkest of all subjects, the History 
 of Life. 
 
 I shall now attempt, as shortly and as clearly as I can, 
 to state in abstract what are the most prominent con- 
 clusions which we may now consider as established, and 
 what is the nature of the evidence on which the proof 
 is founded. 
 
 The rocks composing the crust of the earth may all be 
 divided into two great classes rocks which have been 
 in the condition of melted matter from the action of heat, 
 and rocks which have been formed by simple deposit from 
 water. The fire-rocks are, in general, quite easily dis- 
 tinguishable from the water-rocks. Everybody knows 
 ' whinstone " and granite by sight, and these are typical 
 specimens of the class to which they belong. As I have 
 something special to say in respect to this class of rocks 
 in the local description with which I shall conclude, we 
 may at present confine our attention to that other great 
 class of rocks which have been deposited by former seas, 
 and which occupy by far the largest part of the whole 
 area of the earth. They are known by every mark by 
 which the human eye and the human reason can identify 
 the natural effects of a well-known and familiar cause ; 
 they are known by the arrangement of their materials 
 by the parallel beds or strata in which they lie and, 
 above all, by the immense profusion of shells and other 
 marine productions with wljich they are filled, and of 
 which, in many cases, they are almost entirely composed. 
 Those of you whose attention has not been specially 
 
14 
 
 called by study to the subject, or who have not travelled 
 much in other parts of the world, have probably a very 
 inadequate idea of the distinctness with which these 
 great characteristics are seen in the rocks which have 
 been formed by water ; because it does so happen that in 
 this country a very large proportion of the mountains 
 are formed, either of rocks not stratified at all, or of 
 rocks whose stratification has been much obliterated and 
 obscured by subsequent changes, and which are, for the 
 most part, entirely destitute of fossil remains. But I wish 
 I could give you by description any adequate idea of the 
 magnificence and the distinctness with which, in some 
 other parts of Europe, the mountains of water-rock speak 
 to us of the origin of their materials. I have lately 
 returned from a visit to the Austrian and Bavarian Alps, 
 which are, to a great extent, entirely composed, from 
 base to summit, of stratified limestone, and frequently so 
 steep and precipitous that there is neither grass nor wood 
 to conceal or obscure their structure. They stand up 
 in stupendous precipices of perpendicular rock, all 
 striped and ribanded with the parallel lines of original 
 deposit lines which no subsequent baking, or heav- 
 ing, or fracture, or falling in has been able to efface. 
 We know of one agency, and of one agency alone, whose 
 mechanical effect is to arrange solid materials after this 
 fashion and that is the agency of water ; and though 
 the mind is oppressed by the idea of the long ages which 
 must have been required for the accumulation, one above 
 the other, of these layers of limy mud to the depth perhaps 
 of 7000 or 8000 feet, still magnitude and time are the only 
 difficulty ; the effect on a smaller scale is seen, or may be 
 seen, in the deposits of our rivers, and our seas. Nor are 
 there wanting those other indisputable proofs of the reign 
 of Ocean the remains of its shells, and its corals, and its 
 fish. On the occasion to which I have referred, we had 
 
14 
 
 before us, during the half of a day's journey, one noble 
 mountain of most peculiar outline, which reared its slop- 
 ing top, terminating on one side in a magnificent preci- 
 pice, to the height of some 7000 feet above the level of 
 the sea, and reminding us, more than mountains usually 
 do, of the somewhat ideal forms in the pictures of Sal- 
 vator Eosa. At the end of our day's journey, we found 
 that our halting-place for the night was near its foot, and 
 that it was a mountain celebrated for the fine view it 
 commands over the surrounding Alps. Some of our party 
 next day ascended to the top, and from high among its 
 ledges of weathered rock, all roughened and honeycombed 
 with the wear and tear of unnumbered years, they brought 
 down fragments, some consisting entirely of broken shells, 
 and others bearing on their surface, in the very form and 
 position in which they had lived and died, the most 
 fragile tenants of that ancient sea. 
 
 There is still living, in some of our deep-sea lochs in 
 the Western Highlands, a kind of shell called Terebratula, 
 varieties of which have existed through a vast number of 
 pre-existing worlds. It is a two-valved shell, like the com- 
 mon cockle, but has this peculiarity, that at the hinge one 
 valve overlaps the other, and is provided with a small 
 orifice, from which proceed little fibres, which serve to 
 anchor the shell to stones or seaweed. There is only one 
 species now existing in our seas. It is comparatively a 
 rare shell ; but I have myself dredged it in Loch Fyne, and 
 it is to be found in other localities of our western coast. 
 Well, here is a specimen of this peculiar family of shells 
 which was found that day high up on one of the weathered 
 surfaces of the mountain. It is a small, delicate shell ; 
 yet it is as perfect as if it had been preserved in cotton, 
 with the little orifice of its anchor as distinct as when it 
 lived. It is clear that here* we have it upon the spot on 
 which it had existed, for it is too fragile to have borne 
 
15 
 
 transportation, unless for a short distance in deep and 
 quiet water, and on a bed of soft and smooth material. No 
 amount of reading, or of second-hand knowledge, can bring 
 such conclusions so forcibly before the mind as scenes like 
 these ; and I confess I have never been so much im- 
 pressed by the magnitude of geological phenomena as 
 when looking at the mighty rampart of those Austrian 
 Alps, separated by the main chain from the nearest exist- 
 ing sea, yet bearing such visible evidence of the time 
 when their materials were being accumulated in the great 
 waters of some former world. 
 
 But although it so happens that, in this part of Scot- 
 land at least, we have no mountains which exhibit so 
 distinctly the stratified arrangement, and the peculiar 
 fossils of the water-rocks, precisely the same phenomena 
 are to be found close to the spot where we are now 
 assembled. They happen to be less conspicuous, because 
 the strata, instead of having been lifted and broken into 
 the form of mountains, are comparatively little elevated, 
 and are covered by the soil. But you have only to look 
 at the sections of strata through which our coal-mines 
 pass, to see precisely the same evidence of that peculiar 
 arrangement in parallel beds or strata which characterises 
 the water-rocks. I very well recollect that before I took 
 much interest in this branch of science, I used to imagine 
 that the representation of strata which we see in geo- 
 logical drawings and sections, was an ideal representa- 
 tion, and that in nature the rocks were never arranged 
 in such precise and parallel lines. It is possible that 
 there may be many here who have seen only the ap- 
 parent confusion of the superficial materials of the earth 
 its soil, and stones, and fragments and who are under 
 the same impression. To disabuse them of this idea, I 
 need only point out these actual sections of the rocks 
 cut through in some of the coal-mines in this district. 
 
16 
 
 In one of them there are many scores of beds of distinct 
 and separate materials, amounting in all to upwards of 
 400 feet, and all arranged with the same parallelism to 
 each other. 
 
 If any one should ask whether we have any evidence 
 of similar effects being produced by water now if sands, 
 and clays, and gravels are being now arranged in similar 
 fashion by the rivers or by the sea, the answer is easy 
 we have such evidence in abundance. A large sum is 
 annually expended by this city, or at least by the trustees 
 of your river, in removing the deposits which the Clyde 
 is yearly forming ; and so rapid is the process, so great is 
 the quantity of material which its waters annually bring 
 down from the country through which it passes, that un- 
 less your steam-dredge were constantly at work, our own 
 lives would probably suffice to see the channel destroyed, 
 and the river cease to be navigable by vessels of any 
 considerable size. And what the Clyde is doing now, 
 we know that it had been doing during the unknown 
 period of time which has elapsed since it began to flow. 
 During that time the Clyde has brought down and depo- 
 sited a very large part of the ground on which this city 
 is built ; and we have the means of measuring the depth 
 of the strata it has formed since our rude forefathers first 
 began to navigate its waters. I have been favoured by 
 Mr John Buchanan, of this city, with a note on what 
 may be called the fossil canoes found at various periods 
 imbedded in the deposits of the Clyde. It appears that, 
 during the last eighty years, no less than seventeen have 
 been discovered. One of them was found in digging the 
 foundation of St Enoch's Church, twenty feet below the 
 surface of the ground ; another was found in digging the 
 foundations of the Tontine Buildings at the Cross ; a 
 third so high up as on the slope near the New Prison. 
 ISlow all these ancient canoes were covered by sands and 
 
17 
 
 gravels brought down by the river in whose waters they 
 had sunk. How many centuries must have elapsed since 
 that early navigation of the Clyde it would be difficult 
 to determine. But if, by chance, one of the great steam- 
 ships for which the same river is now so justly celebrated, 
 should ever be sunk, and silted up in its ever-growing 
 sands, the comparison will afford to the geologist of 
 some future stage of the world an illustration sufficiently 
 curious of the progress of mankind ! 
 
 Having, then, arrived at the clear conviction that 
 the stratified rocks of the earth have been all formed in 
 the same way, by deposit from water, you will see at 
 once that the first most obvious indication of their relative 
 antiquity is simply their overlying or underlying each 
 other. The stratum of sand in which the canoe was 
 found, was more ancient than all the other strata which 
 lay above it ; the most recent deposit of the river being, 
 of course, always the uppermost. This, then, is the first 
 groundwork of classification in geology ; and wherever it 
 can be applied, it is the most direct and conclusive 
 evidence of the relative age of strata. But we must 
 remember that, in the very nature of things, we cannot 
 expect in all cases to have that evidence to go by. The 
 sea or the river which deposited a layer at one place 
 deposited nothing at another place, because that other 
 place was not at the time subject to the flow of its waters. 
 All those portions of the earth which formed dry land dur- 
 ing each geological period, received, of course, no deposit 
 from the sea of that period ; and as there may be, and are, 
 such portions of the earth which are not only dry land 
 now, but have been dry land during many successive 
 epochs, we cannot expect to find upon them any overlying 
 strata. We cannot therefore judge of their own age by 
 the indication of what lies above. 
 
 Here, then, lies one great value of the discovery of 
 
 B 
 
18 
 
 Smith, that each stratum, or set of strata, among all the 
 water-rocks, is characterised by its own peculiar fossils ; 
 so that, by these fossils, each set of strata can be recog- 
 nised, although found entirely separate from others with 
 which it is elsewhere associated. Of course this dis- 
 covery was itself first founded on the direct evidence of 
 overlying or underlying position. Thus, for example, on 
 the east coast of England and I may add, also, in some 
 spots of the north-east coast of Scotland a series of sand- 
 stone beds, generally of a creamy or whitish colour, are 
 seen to lie over another set of strata composed of mud 
 and clays. The sandstones got the name of Oolite, and 
 the clays were called " Lias." Each have their own 
 peculiar fossils ; and in the lower of these strata they 
 are very peculiar indeed. Now, when these last rocks 
 are found elsewhere containing the same fossils, although 
 there may not be actually present any overlying sand- 
 stones, we know that the rocks containing them are older 
 than the oolite, and that the oolite, if it had existed at 
 all at that spot, would have been found above, because it 
 is the product of a later sea. 
 
 In like manner, on the south coast of the Isle of Wight, 
 whose rocks present one of the finest natural sections 
 in Britain, the chalk hills are seen to be supported 
 below by a great series of sands and sandstones ; and, 
 again, to bear upon their own backs another great series 
 of strata, chiefly of clay and lime. All these have their 
 peculiar fossils. Now, it is quite common to find all 
 these strata separate from each other the sands without 
 any chalk upon their top the clays and limestones with- 
 out any chalk below and the chalk dissociated from 
 both. But by means of the fossils we can always identify 
 these separate strata ; and, though found alone, we know 
 their relative age, because at* some particular place we 
 have found the key to their relative position. 
 
19 
 
 Proceeding, then, on this principle of classification, 
 the whole stratified or water-rocks of the world have 
 been found to range themselves in a definite order, an 
 order of position one above the other, involving an order 
 of time, one after the other. Here is a list, or section of 
 
 600 /. 
 
 ioo \ RECENT-LIFE 
 3oo } STRATA. 
 
 MM 
 
 MIDDLE-LIFE 
 STRATA. 
 
 Granitic Rucks 
 
 them, arranged according to that order a section which 
 I owe to the kindness of my friend, Professor H. D. 
 Rogers, whose services, transferred from the other side 
 
20 
 
 of the Atlantic, we have had the good fortune to secure 
 for our own University. You will, of course, understand 
 that there is no one spot on earth where all these rocks 
 are found together. There are many where there are 
 none of them at all ; others, where there are only the 
 topmost, and latest or only the lowest and most 
 ancient; others, again, where some of the middle rocks 
 occupy the surface, with no evidence that any later sea 
 deposited any materials above them. You will have 
 no difficulty in understanding how this should be the 
 case, if you have mastered the leading idea that, as all 
 the stratified rocks have been laid down by water, and 
 as there were probably always large portions of the earth 
 above water, we cannot expect to find upon those parts 
 deposits to which they were never subject. And, then, 
 there is another reason why many strata should be want- 
 ing, even where they were once existing ; and that is, 
 that they have subsequently been washed away. We 
 have the clearest evidence of this removal in number- 
 less cases ; one example of which I shall bring to your 
 notice in the local description with which I shall 
 conclude. 
 
 This great series, then, of water-rocks which have been 
 found to bear the relative position indicated in this 
 section, have been classified into three great divisions. 
 There has been some confusion in the naming of them, 
 because certain terms which w^ere applied before the true 
 principle of classification had been discovered, had got 
 such hold, that science has never got rid of them, and 
 they now mix inconveniently with names founded on the 
 true principle of division. But the simplest statement 
 of the case is this that with reference to order of time, 
 the rocks have been divided into Primary, Secondary, 
 and Tertiary ; and that these correspond with another 
 division founded on the difference in the fossils the 
 
21 
 
 strata of Old-Life, of Middle-Life, and of Eecent-Life. 
 The Old-Life strata include the lowest and oldest of all 
 the strata which contain any remains of life, and termi- 
 nate with certain rocks which lie above the Coal-measures. 
 The Middle-Life rocks extend from the top of these to 
 the chalk inclusive ; whilst the Recent-Life strata include 
 all those which have been deposited since the period of 
 the chalk, down to the latest changes before the com- 
 mencement of the existing state of things. There is a 
 fourth class, the lowest of all, to which the term Primary 
 was originally restricted, in which no remains of life 
 whatever have been found. 
 
 The names thus given to these great divisions are 
 expressive of an important fact, viz. : that the types, or 
 patterns of organic life that is to say, the animal and 
 vegetable forms differ from the forms now living, more 
 and more widely in proportion as we go back in time. 
 The Old-Life fossils are of forms, so to speak, antiquated 
 and obsolete ; those of the Middle-Life rocks have a com- 
 paratively modern aspect ; whilst the Tertiary, or New- 
 Life strata, show a rapid approximation to the Flora 
 and Fauna of the living world. 
 
 It cannot be too distinctly impressed upon beginners 
 in Geology that, in recognising the different formations, 
 mere external appearance, or mineral aspect, can never 
 be safely trusted. Some of them have names which pro- 
 fess to be descriptive, but are not. For example, one 
 great group of the Old-Life Rocks has been called " the 
 Old Red Sandstone ;" and it is true that its prevailing 
 beds are sandstone, and are red. But it includes a great 
 variety of beds which are not sandstone at all, and are 
 never red ; and these last, too, are generally those which 
 contain the characteristic fossils. On the other hand, 
 there are a vast number of Red Sandstones which do not 
 belong to this group at all. An instructive example of 
 
22 
 
 the deceptiveness of such names has just occurred in a 
 discovery recently made in the north of Scotland. Those 
 who have seen its north-west coast cannot fail to have 
 observed some very remarkable isolated mountains, which 
 rise along the shores of Eoss and Sutherland. They are 
 in great proportion composed entirely of Red Sandstone, 
 and they have always been referred to by Hugh Miller 
 and others, as belonging to the " Old Red" formation, and 
 as proving, by their shape and the position of the beds, 
 both the depth to which that deposit had once extended, 
 and the extent to which it had subsequently been washed 
 away. "Well, but during the course of the last year one 
 little band of limestone has been found, belonging to 
 these same beds, which, alone of all the many beds 
 around it, contained some fossils. These have been 
 recognised as belonging not to the " Old Red " at all ; 
 but to a group of rocks older still even to the lowest 
 member of the Old-Life Rocks. Consequently these 
 mountains have been now classified as belonging to the 
 " Cambrian," or " Lower Silurian" strata. Thus, though 
 they are " old " " older," indeed, than they were sup- 
 posed to be though they are sandstone, and red sand- 
 stone too, nevertheless they do not belong to the " Old 
 Red Sandstone." 
 
 The essential definition of a geological formation is 
 not a series of beds of any given colour, or texture, or 
 mineral composition ; but a group of strata characterised 
 by a definite assemblage of animal and vegetable life. 
 
 Hitherto I have spoken of the discovery of the differ- 
 ent strata having each their peculiar fossils, only as a 
 means of identifying them when found separate from 
 each other, and thus of recognising their proper place with 
 reference to others and in reference to time. But for this 
 purpose alone, any other peculiarity which was equally con- 
 stant, would have been equally good. If, for example, it 
 
23 
 
 had been found that the strata lying under chalk were 
 always of a certain colour or a certain texture, that colour 
 or texture might have been sufficient to identify the posi- 
 tion and age of those rocks when found alone. But the 
 discovery in respect to fossils involved far more than this ; 
 it opened up an entirely new subject, new even to specu- 
 lation, absolutely new to science. For, just think what 
 fossils are, and what is involved in the discovery that 
 each successive series of rocks have each their peculiar 
 kinds. Fossils are the remains of Life. They record, 
 therefore, the form in which life has been embodied in 
 the worlds which preceded our own. We are familiar 
 with the idea of variety almost endless variety in the 
 forms of life. It seems vast when we regard it, even in 
 our own country ; it seems still vaster when we regard it 
 in connection with other countries, in many of which we 
 should not recognise, perhaps, a single plant, or insect, or 
 bird, or beast, identical with those which we know at home. 
 When we see a new plant or a new animal, we know very 
 well that it is only new to us ; and we conclude, without 
 doubt, that it has existed since the world began, although 
 we have not been in a position to observe it. But there 
 is one thing of which we have no experience, arid can 
 hardly form even an idea that is, the first introduction, 
 or the first creation, of a new form of life. Yet this is 
 the idea with which we must endeavour to familiarise our 
 mind when we come to study fossils. For what do we 
 mean when we say that each new series of strata in the 
 history of the earth has a new or peculiar set of fossils ? 
 We mean that new plants and new animals have been 
 formed from time to time, replacing others, which, in the 
 same period, had died out and become extinct, each new 
 series differing in greater or less degree from the series 
 preceding ; we mean that creative power has been 
 exerted, not, as we are apt to imagine, once for all, but 
 
24 
 
 continuously, perpetually ever renewing its own work, 
 with some diversity of pattern some change of struc- 
 ture some variety of purpose. And thus we find that, 
 as in respect to the distribution of land and sea, our 
 existing world is but one of the many aspects which the 
 earth has assumed in the course of time ; so in respect to 
 all the living things by which, it is inhabited they do 
 but represent the latest of the thousand forms in which 
 Life has been embodied in the world since its records 
 began to be written in the rocks. 
 
 Began ! I have used the word instinctively, and 
 rightly, in so far at least as it introduces us at once to 
 the next great division of our subject. Began ! Have 
 we then found that which Dr Hutton declared he could 
 not find in Geology, some " vestige of a beginning 1 " 
 Hitherto w r e have been on ground which is not debate- 
 able. That the strata of the earth have been formed by 
 water that they can be arranged in the order of time 
 that they record the continual introduction of new 
 plants and animals to replace others which became ex- 
 tinct, these are conclusions about which there is no doubt 
 whatever ; they are truths as firmly established as any 
 in the whole range of the Physical Sciences. But with 
 the further question which I have now suggested, we 
 enter upon ground, every step of which is still contested. 
 Without concealing my own opinion on the main points 
 of controversy, my chief desire now is to state clearly 
 what those points are, and what is the nature and amount 
 of evidence wherewithal they are to be decided. 
 
 Three questions naturally occur to us when we hear 
 that the Kocks contain a history, as it were, of organic 
 life that they are shelves, as it were, of a great museum 
 arranging the plants and animals of preceding worlds in the 
 order of their creation. First, Do we find any evidence 
 of a time when the earth was not yet fit for the support 
 
25 
 
 of life of a time, therefore, before life had begun to be 1 
 Secondly, Do we find any evidence that in the creation of 
 living things the Creator had worked upon a plan of 
 progress, of advance, from a lower to a higher type of 
 organisation \ Lastly, Can we see, however faintly, any 
 trace or indication of a rule or law according to which 
 creative power has worked 1 
 
 Profound as these questions are in their bearings, and 
 in respect to the farther questions which branch out from 
 them in every direction, you must not be scared by the 
 long words and the technical language in which scientific 
 controversies are conducted, or imagine that there is 
 really anything very difficult to understand in the argu- 
 ments on either side. In respect to the first of these 
 questions, for example viz. whether, as regards the 
 introduction of life upon our planet, we have any vestige 
 of a beginning, the case may be very simply stated. It 
 is certain no geologist denies it that the lowest and 
 oldest of our stratified rocks are entirely destitute of fossil 
 remains. But many geologists argue against the conclu- 
 sion that life did not exist when those strata were de- 
 posited, mainly upon two grounds. First, they say that 
 these rocks, from the very fact of being the oldest in the 
 world, have been subject more repeatedly than others to 
 the various agencies of mineral change ; and that it is a 
 known effect of some of these to destroy arid obliterate 
 fossils, where we have every proof that they have existed 
 in abundance. Secondly, it is sometimes said that we 
 can never be quite sure of the non-existence of fossils until 
 our search has been more complete than it has yet been ; 
 arid rocks of much later date are also frequently found 
 equally destitute of fossils, although in their case it is 
 known, from other examples, that contemporary life existed 
 in the world. To the first argument it is replied, that 
 many of the old strata, which are destitute of fossils, bear 
 
2G 
 
 no evidence of any baking, or crystallisation, or any other 
 mineral change which could obliterate fossils if they had 
 ever existed ; whilst to the second. I think it quite suffi- 
 cient to reply, that our conclusions must be founded on 
 such evidence as we have. These rocks have now been 
 examined in every region of the globe, and though they 
 contain all the usual varieties of original substance, lime, 
 sand, and clay, the search has always led to the same 
 negative result. Therefore until farther search has actu- 
 ally led to the discovery of some fossils in those strata, 
 we are entitled to assume that their non-existence indi- 
 cates that life, if it existed at all, had not begun to be 
 abundant in the world, or was restricted to low and per- 
 ishable forms. I may mention that the rocks to which I 
 now refer, are largely represented in the west of Scot- 
 land. The rocks called gneiss and mica- slate belong 
 to them. The whole of that fine range of hills which 
 faces the mouth of the Clyde, and forms so beautiful an 
 outline from the quay of Greenock, is composed of mica- 
 slate ; whilst gneiss is the foundation-rock of the country 
 all along the north-western coast of Scotland. Any one 
 of you who can find in any one of those strata, any 
 indication of a shell or other fossil, will have made an 
 important discovery in geological science. He will have 
 carried our knowledge of the history of life far back 
 into the depth of time ; and he will have rendered it 
 far more doubtful than I think it is at present, whether 
 we have or have not found in Geology some " trace of 
 a beginning," at least in respect to the introduction of 
 life. 
 
 And then, as regards the second question viz. whe- 
 ther in the long series of specimens we possess, arranged 
 in chronological order, we <5an detect any signs of pro- 
 gress, or of advance from a lower to a higher type of 
 animal or vegetable life ? The evidence on this point 
 
27 
 
 also can be understood by all. It is an unquestioned 
 fact, that in the lowest and oldest rocks no animal 
 remains have been discovered, except the remains of 
 corals, shell-fish, and certain peculiar kinds of crab. It 
 is equally admitted, that through a long series of strata 
 which are the next highest and the next oldest, there is 
 still an entire absence of warm-blooded animals, although 
 the next orders in creation fish and reptiles are begin- 
 ning to appear. It is farther certain that the first warm- 
 blooded animals which do appear, are of that low type 
 which exists now principally in Australia the Pouched 
 or Marsupial animals creatures which are known by 
 keepers of wild animals to be the most stupid and 
 indocile of all. Yet farther, it is equally certain that as 
 we rise through the succeeding strata, the higher warm- 
 blooded animals rapidly increase, until, in the later ages 
 of the earth, we are astonished by their abundance, and 
 not less by their gigantic proportions. Last not least 
 in this catalogue of admitted facts all geologists admit 
 the telling fact that Man was the last and latest of 
 created beings neither his remains nor his works being 
 ever found in any but the most superficial deposits of 
 our existing world. 
 
 But perhaps some of you may be inclined to ask how, 
 if this be a correct statement of undisputed facts, there 
 can be any question at all that there has been progress 
 in the order of creation from a lower to a higher type "? 
 Well, one ground of objection is this : " Very true, it 
 is said, the oldest rocks contain nothing but shell-fish 
 and crabs. But what would you expect in strata which 
 bear evidence of having been formed in deep sea-water 1 
 You can't expect to find very often there the remains of 
 land animals, though such may have existed abundantly 
 at the time on some distant shore." To which again it is 
 replied, "Recollect there are higher warm-blooded animals 
 
28 
 
 which live in the sea as well as on the land. These are 
 Whales, and Grampuses of various kinds ; and in later 
 strata, equally the produce of deep-sea water, you do find 
 remains of such sea animals in abundance, but none, not a 
 vestige of them, in the oldest rocks/' And again, in reply 
 to the argument that we have not searched widely 
 enough to establish the absolute non-existence of such 
 remains, or of others of a high type, it is answered, as 
 before, that we must be guided in our conclusions by 
 such evidence as we have ; and that until some dis- 
 covery is made in the older rocks of warm-blooded 
 animal life, we have a fair right to assume that they 
 did not exist. Then there are some other arguments 
 which, though less direct, are in my mind of great 
 strength in favour of the fact of progress in the creation 
 of animal Hfe. Throughout a great part of the secondary 
 rocks there is an immense development of reptile life 
 reptiles of every form and size, adapted for the destruc- 
 tion of other animals both by land and sea. I think 
 their number and variety, together with the total absence 
 of higher animals, give us the strongest reason to believe 
 that those offices of destruction which are now performed 
 by warm-blooded and more highly organised beasts of 
 prey, were in earlier ages of the world assigned to those 
 monstrous lizards and crocodiles; and I own that I 
 regard the universally-admitted fact that the creation 
 of man was the last and latest work, as one which 
 almost leads us to expect as probable an analogous rule 
 in the preceding history of the world. You will readily 
 understand the interest which this question gives to 
 every new discovery of fossils which casts any light upon 
 it, or affords any corroborative evidence upon one side 
 of the controversy or the other. Within a very short 
 time during the course of the last year one dis- 
 covery has been made in the south of England which 
 
29 
 
 carries down the existence of warm - blooded quadru- 
 peds lower farther back into time than they had before 
 been known to exist. It does not appear to me, how- 
 ever, that the discovery affects the balance of evidence 
 one way or another ; for it turns out, on examination, 
 that all the little quadrupeds which have been brought 
 to light are of the same low Marsupial class which had 
 been already found lower than any other in the strata. 
 
 I come now to the third great question by far the 
 most interesting, but by far also the darkest whether 
 we can trace, in this history of life, any sort of indication 
 of the employment of secondary causes in the introduc- 
 tion of new plants and animals. It is impossible that 
 this question should not sometimes present itself to our 
 minds when we contemplate the amazing fact, that crea- 
 tion has been not the special act of some special time, but 
 a long series of acts constantly repeated and renewed. 
 What should we have seen had we been present at the 
 time and on the spot where some new form of life let 
 it be the least and lowest came fresh from the hands of 
 God 1 Should we have seen, for example, some existing 
 shell become suddenly obedient to a new law of growth, 
 and spread out in patterns which had been unknown 
 before ; or should we have seen the inorganic elements of 
 which all animal frames consist, gather themselves vis- 
 ibly together, and be moulded before us into some new 
 form of life ? The wonder of the question comes more 
 home to us when we put it in reference to some of the 
 higher and more prominent types of animal life the 
 monstrous river-horse, the huge and sagacious elephant, 
 or the various races from which our domestic animals 
 have been derived. In regard to all of them we can see 
 backwards to a time when none of them existed, and a 
 time comparatively recent when they began to be. What 
 idea can we form of the method of such a work \ Is it 
 
30 
 
 possible that, by the suspension of the more ordinary laws 
 of increase, or by the disclosure of a higher law hitherto 
 concealed, some pre-existing animal should become the 
 progenitor of a race wholly unlike itself ; and if we had 
 been then living on the earth, should w^e have seen 
 nothing but an apparently monstrous birth : or should 
 we have seen suddenly fashioned from the dust, in com- 
 plete stature, some creature endowed with new powers, 
 and destined for new enjoyments \ 
 
 To these questions, however eagerly we may ask them, 
 science hitherto has yielded no reply whatever. Such 
 evidence as it affords is abundantly sufficient to negative 
 that theoretical solution which was attempted a few years 
 ago in the famous doctrine of Development. There is no 
 appearance whatever of one animal having grown into 
 another. Each new form appears perfect and complete, 
 continuing identical until it disappears for ever. There 
 are indeed links, such as exist now between contempor- 
 ary animals, such as connect the lion with the polecat, 
 or the eagle with the vulture. But there is no trace in 
 nature of one having been derived by gradual passage 
 from the other, or that any animal ever underwent any 
 essential modification of its structure. We leave then 
 this problem as we found it ; thinking it highly probable, 
 that of the mode and manner of creation we shall always 
 
 remain in ignorance. 
 
 One discovery, indeed, has arisen out of the more re- 
 fined examination of animal forms, which is very wonder- 
 ful, very mysterious, and in one sense may be said to 
 indicate a law which has been followed in the exercise of 
 creative power. It has been clearly established by the 
 researches of Professor Owen, that in respect to one great 
 department of the animal kingdom I mean that great 
 class called the vertebrata, or animals the most essential 
 element of whose skeleton is a back bone, divided into 
 
31 
 
 segments called Vertebrae, it has been proved, I say, 
 with reference to them, that the special adaptation of new 
 animals for special purposes and special spheres of life, has 
 been so pursued as to be consistent with adherence to one 
 type or pattern of organic structure ; so that all the essen- 
 tial parts of that structure have been more or less retained, 
 although modified (how, we can form no idea), to suit 
 the particular powers, instincts, and enjoyments of each 
 new form of life. Professor Owen illustrates this doctrine 
 of comparative anatomy by referring to three different 
 animals in the existing world, as widely separate appa- 
 rently as any three that could be selected for the purpose : 
 the mole which burrows in the earth the bat which flies 
 in the air the whale which swims in the sea. Well, if 
 we compare the two fore-limbs of these three animals, we 
 find that all of them, though formed for purposes so 
 totally diverse, are composed of exactly the same number 
 and the same relative disposition of bones. In the mole 
 they are shortened and stiffened to enable the animal to 
 burrow. In the bat they are lengthened and attenuated, 
 with a web stretched between the fingers to adapt the 
 animal for flight. In the whale all the same elements of 
 structure are packed into a paddle or fin, to support and 
 propel the animal in water. The same principle is found 
 to run throiigh the whole Vertebrate order, and more or 
 less distinctly it is observable in every department of 
 creation. Upon it, perhaps, depends much of that wonder- 
 ful combination of unity with variety, which has long 
 been recognised as one main element in the inexhaustible 
 beauty of all the works of God. 
 
 One other great question, much disputed, I must 
 notice here : How far have the vast changes recorded 
 in the rocks been slow, gradual the result of forces 
 such in all respects as are in operation now : how far 
 have they been sudden, violent the effect of convul- 
 
32 
 
 sions connected with a less advanced and less stable 
 condition of the surface of the globe ? It is certain that 
 the tendency of all early speculations on Geology was to 
 sink too much the element of time to rely too much on 
 the element of force. All geologists now, however, are 
 agreed in requiring such periods of time as may com- 
 pare with the similar demands which Astronomy makes 
 upon our conceptions in regard to space. Still, the ques- 
 tion remains, Have those vast periods of time been 
 marked by nothing more than a mere heaping-up or 
 accumulation of identical results 1 Has there not been 
 a spending of activity an exhaustion of force a pas- 
 sage from periods of early tumult and preparation, to 
 others of comparative stability and rest 1 
 
 There are three great sources of evidence from which 
 our arguments on this question must be mainly drawn : 
 First, there is the position in which the rocks are now 
 seen, with reference to the mechanical forces of which 
 that position is an index and a measure. Secondly, 
 there are the changes, whether sudden or gradual, 
 which have taken place in the animals and vegeta- 
 tion of the world. And, Thirdly, there are arguments 
 somewhat more hypothetical, but having, nevertheless, 
 very strong foundations in reason and analogy, derived 
 from the probable perhaps it may be said the neces- 
 sary condition of our globe as a planetary body. I 
 cannot now, of course, give even a sketch of all the 
 arguments on each of these heads which this great ques- 
 tion has called forth in support of different conclusions. 
 My own conviction undoubtedly is, that throughout the 
 long ages of Geology before the Human * period, the 
 earth was subject to agencies of change such as have 
 never been exerted in any similar degree since man was 
 born. It is very true that these agencies, or others of a 
 similar nature, are still giving evidence of their exis- 
 
33 
 
 tence and their power ; it is very true that within the 
 memory of man they have produced, and are even now 
 producing, changes which, though small and slow, would 
 produce, at the compound interest of some million years, 
 vast aggregate results. We know of forests where our 
 rude forefathers hunted the wild ox and the deer, 
 which are now covered by the sea, and buried deep in 
 the sands which Ocean is ever heaping on its spoils; 
 we know of cataracts of melted stone, poured forth 
 from internal reservoirs of fire, destroying one vege- 
 tation, and preparing new surfaces for another ; we 
 know of quakings and convulsions of the earth, which 
 only subside after they have added to the height of 
 mountains, or lowered whole territories under the level 
 of the sea ; nay, more, we know of a whole country 
 in our own division of the globe a considerable part of 
 Europe which, as if by some mighty and unknown 
 machinery, is slowly, steadily, imperceptibly being lifted 
 up so that every century sees the tide mark a lower 
 and lower level on its rising rocks. Still, no accumu- 
 lation of changes such as these will account for all the 
 phenomena which are familiar in Geology. In those 
 Austrian and Bavarian Alps to which I have before re- 
 ferred, I could not help thinking the evidence singularly 
 distinct. Time enormous, incalculable in its duration 
 is indeed required for the accumulation of materials 
 for their consolidation for the elevation of that mass of 
 strata. All these operations may have been slow and 
 gradual. But there must have come a time when the strain 
 or pressure was too tremendous for the materials to bear, 
 and when, falling in and breaking up, they were rent and 
 riven like the floes of arctic ice. All their surfaces 
 are torn and broken, and we pass through the chasms 
 they have left, seeing on either hand, widely separated 
 from each other, strata which must have been once con- 
 
 c 
 
34 
 
 tinuous, but are resting now in opposing slopes, which 
 may be traced from the bottom of the valleys to the 
 levels of eternal snow. Then there are other regions 
 of the globe our own Western Highlands among the 
 number where the position of the strata can only be 
 accounted for by supposing that in whole districts they 
 have suddenly fallen inwards, splashing up between 
 the leaves of their deposit the melted granites which lay 
 below. It may be that forces capable of producing simi- 
 lar effects are slumbering still ; but assuredly they have 
 never been called into similar exertion since the birth of 
 man. 
 
 In regard to the changes of Animal and Vegetable 
 life, it is, I think, fair to admit that the progress of 
 discovery has tended to fill up gaps, and to show that 
 the passage from one set of inhabitants to another 
 was more slow and gradual than at first it may have 
 appeared to be. This, however, does not materially 
 affect the question ; because the most violent changes 
 on the surface of the globe have probably affected only 
 small portions of that surface at a time, and might 
 have very small effect on the destruction of races more 
 widely distributed. There are still, however, some 
 great chasms to be filled, one in particular between 
 the deposition of the chalk and the earliest succeeding 
 strata. How long that period may have been we 
 know not : but it seems pretty clearly ascertained that 
 it was one through which no living thing survived. 
 When creation again appears, it is with a face entirely 
 new. It would be difficult to suppose that this period, 
 in respect to mere lapse of time, represents a greater 
 transition than any other in geology. The inference 
 therefore is, that it was a period of greater physical 
 change. 
 
 As regards the arguments derived from the early 
 
35 
 
 condition of our globe as a Planetary Body, it may be 
 enough here to say that if, as appears to be most 
 probable, the earth was ever in a condition of greater 
 heat nay if, as seems almost ascertained, its centre is 
 even now far hotter than its surface, then it is certain 
 that the mere lapse of time must have been producing 
 a constantly increasing change, which would connect 
 itself naturally with some of the most remarkable 
 features of geological history. 
 
 It must be owned, however, that at least one very 
 prominent feature in that history receives no explana- 
 tion from the hypothesis of a constantly decreasing heat. 
 Down to a certain period, and that almost the last and 
 latest, all the facts, so far as we yet know them, are at 
 least consistent with that supposition. There seems to be 
 no doubt whatever that the animals and the plants of 
 former worlds indicate that a warmer temperature 
 prevailed over the globe than prevails at present. Even 
 the seaweeds of the older rocks are now represented 
 by genera peculiar to southern seas. No vegetation 
 now known in the hottest regions of the earth not 
 even that which, on the eastern coasts of tropical 
 America, is the very paradise of botanical wonders 
 equals or approaches the wonderful vegetation from 
 which the coal-measures have been derived. Yet that 
 vegetation flourished, not only in this our own latitude, 
 now temperate, but also in arctic regions now covered 
 with perpetual ice and snow. And after that, all through 
 the secondary ages, both the animal and vegetable remains 
 are allied more or less distinctly to those families which 
 prevail in the warmer latitudes of the world. Again, when 
 we come down to the beginning of the Tertiary ages, 
 we find, in a deposit at the mouth of the Thames, fossils 
 in vast abundance, very similar to those which Indian 
 floods are now accumulating in the Delta of the Ganges. 
 
36 
 
 In the succeeding strata, the plants and animals assume 
 more and more closely the character of existing forms, 
 indicating a steady approximation to those conditions of 
 climate which obtain in the existing world. But, strange 
 to say, between the latest of these Tertiary strata and 
 man's creation, there seems to have intervened, at least 
 all over the Northern Hemisphere, a period of infinitely 
 greater cold than that to which we are now exposed. As 
 compared, therefore, with that penultimate period in the 
 past history of the globe, its climate has been changing, not 
 from a greater to a less degree of heat, but, contrariwise, 
 it has been getting warmer. So far as this singular fact 
 bears upon the main question, it seems to favour the 
 arguments of those who maintain that the changes of 
 climate throughout the whole history of Geology have 
 arisen from Geographical rather than from Planetary 
 causes from changes in the distribution of Land and 
 Sea, rather than from any which are connected with the 
 internal heat of the globe. Certain it is that the 
 same evidence which proves conclusively that the very 
 last change recorded in Geology has been one from 
 almost arctic cold to that temperate climate which 
 we now enjoy, proves also that the change has been 
 accompanied by changes as remarkable in physical 
 geography. These changes, however, so far as we know 
 their nature, do not appear to have been such as would 
 naturally tend to raise temperature. The height of 
 mountains above the sea, and extent of continent beyond 
 the influence of the sea, are well-known causes of colder 
 climates. But in that very cold period of which I have 
 spoken, our mountains appear to have been very much 
 lower than they are now ; or, to use a graphic expression 
 of Hugh Miller, the whole country " sat low in the 
 water/ 7 Yet its heights seem to have been crowned by 
 glaciers floating icebergs grated along their sides 
 
37 
 
 and shells, for which you must now go to the shores 
 of Iceland, lived in multitudes in our own valley of the 
 Clyde. This fact was first brought to light by my friend 
 Mr Smith of Jordanhill, whose researches, both literary 
 and scientific, must be known to many of you. The 
 shells of an arctic climate, which he was the first to 
 discover, have now been found at very various elevations, 
 up to 500 feet above the level of the sea. Surely it is 
 one of the most wonderful facts revealed by geological 
 science, that, after the whole cycle of former changes 
 had been completed after the surface of the earth had 
 assumed, for the most part, its existing configuration, 
 there has been time for a slow and steady upheaval of its 
 general level, to the extent which those shells indicate, 
 before it was sufficiently prepared for the dwelling-place 
 of men. 
 
 Besides the testimony of shells the most direct and 
 conclusive of all there is another evidence. Many of 
 you may have observed all over the West and Northern 
 Highlands, as also in the lake country of Cumberland and 
 Westmoreland, enormous blocks or boulders of stone, very 
 often perched upon the very tops of the hills. They are 
 rarely if ever fragments of the same rock on which they 
 rest. Very often no similar rock is to be found for miles 
 around. They are, therefore, travellers from a distance. 
 It is impossible, when one's attention is directed to the 
 singular situation of these blocks, not to wonder how 
 they could possibly have been so placed. Wordsworth 
 refers to, and has well described them, in the following 
 lines : 
 
 " As a huge stone is sometimes seen to lie 
 Couched on the bald top of an eminence, 
 Wonder to all that do the same espy, 
 By what means it could hither come, and whence, 
 So that it seems a thing endued with sense, 
 Like a sea-beast crawled forth, which on a shelf 
 Of rock or sand repogeth, there to sun itself." 
 
38 
 
 It is a curious example of the coincidence of true poetic 
 imagination with the truths of nature, even when these 
 truths may not themselves be known, that the illustra- 
 tion here chosen by Wordsworth makes a very close 
 approximation to the actual explanation now given by 
 Geology. The hill-tops on which these boulders lie must 
 have been shoals or shelves of rock comparatively near 
 the surface of the glacial sea, and the floating ice- 
 bergs which then carried, as they do now in Arctic 
 regions, great fragments of rock from the shores where 
 they were originally formed, would, like great sea- 
 monsters, ground upon them, and there remain " sun- 
 ning themselves" till they finally melted and disap- 
 peared, dropping their burden of rock or boulder upon 
 the shoal below. 
 
 I now pass to the Fire-Rocks. They are of all ages. 
 We find them associated with the water -strata under 
 every variety of circumstance which can testify to 
 variety of times and variety of modes of action. Some- 
 times they bear up the water-rocks, as it were, on the 
 heaving back of a subterranean wave. Sometimes they 
 burst through the broken and scattered surfaces with 
 every mark of violence. Sometimes they have insinuated 
 themselves between the beds, and appear as if they 
 were part of the original stratification. Very frequently 
 they fill up cracks and chasms ; and as often they rest 
 in continuous sheets, as if they had spread out with the 
 rapidity of a liquid torrent over vast surfaces of ancient 
 soil, or the bed of ancient seas. Geologists ascribe to 
 this latter mode of occurrence those terraces of what is 
 called trap, which at a distance often look like stratifica- 
 tion, anol specimens of which are conspicuous as you 
 ascend the Clyde on the western front of the Kilpatrick 
 Hills. Sometimes, as I have elsewhere endeavoured to 
 show, we hfve evidence that the water-rocks have sud- 
 
39 
 
 denly fallen inwards, from the shrinkage, or removal of 
 their supports below, and the broken and shattered strata 
 have splashed up the melted granites to the surface in a 
 semi-fluid or viscid state. But of these various modes 
 of occurrence, with the exception of one, the filling up 
 of cracks or chasms by melted matter, we have no know- 
 ledge derived from contemporary observation. In regard 
 to some of them, our conclusions rest on reasoning which 
 is sufficiently clear ; in regard to others they are but 
 conjectural. 
 
 But there is one class of the fire-rocks to which I now 
 turn your attention, of which our knowledge is com- 
 plete, derived from actual observation of what is still 
 being done upon the earth. No phenomenon of nature is 
 so tremendous as volcanic fire. Those who stand for the 
 first time on the crater of Vesuvius or of Etna, commonly 
 receive impressions which can never be effaced. They 
 find themselves in presence of a power terrible in its 
 aspect, unknown in its origin, resistless in its force. The 
 melted matter which is poured forth by volcanoes takes, 
 under different circumstances, very different forms. That 
 which buried Pompeii was merely dust and ashes, that 
 which overwhelmed the neighbouring city of Hercula- 
 neum was melted stone or liquid lava. Where the stream 
 has been thin, and much exposed to the air, this matter 
 congeals in the form of slag, very similar to that which 
 you see produced by smelting-furnaces ; and no words 
 can convey an adequate idea of the desolate aspect of the 
 ground which is covered by this form of lava. Where 
 the stream has been deeper, it hardens into solid stone : 
 whilst under peculiar conditions of cooling, it splits up 
 into rude hexagonal or octagonal columns thus produc- 
 ing that remarkable condition of basalt which so many of 
 you have seen in the famous island of Staff a. There are 
 some volcanic districts in France whose fires have been 
 
40 
 
 long extinct, but where the evidence is as perfect as if we 
 had seen the effect in the course of being produced. You 
 can trace the various streams of lava from the still per- 
 fect craters which have been the points of emission, down 
 to the valleys which they have partly filled, and in which 
 they now support, on magnificent colonnades of basalt, 
 towns and villages, with a rich and beautiful vegetation. 
 
 In the case of Staffa and the neighbouring basalts, as 
 well as in that of the Giant's Causeway in Ireland, all 
 trace has been destroyed of the volcanic vents from 
 which the streams of lava came. But in the case of the 
 Irish basalts, we know roughly the Geological Period to 
 which they belonged, because we find that they have 
 overflowed the Chalk, and must have belonged, therefore, 
 to the Tertiary Ages. The discovery to which I shall 
 now refer may possibly give us a more definite idea of 
 the epoch to which they belong. 
 
 Immediately opposite to the front of Staffa, at the dis- 
 tance of some four miles, there is a low promontory in 
 the Island of Mull, called the Point of Ardtun, remark- 
 able for basaltic columns, smaller but hardly less regular 
 than those of Staffa itself. The cliff in which they are 
 seen is about 140 feet high, and is intersected by a ravine 
 shown in the accompanying diagram. Some years ago, 
 a person in pursuit of otters had occasion to descend this 
 ravine, and taking hold of a piece of rock, which came 
 away in his hand, he observed that it contained the dis- 
 tinct impression of a forest-leaf. Some specimens were 
 soon after sent to me, and having shown them to the late 
 Sir H. De la Beche and stated that they were found 
 underneath a bed of basalt, he explained to me the in- 
 terest which might attach to the discovery ; and I shall 
 here quote from the paper in which I subsequently com- 
 municated to the British Association a full account of 
 the facts, and of the inferences deducible from them. 
 
41 
 
 In the descending order the beds are disposed as fol- 
 lows, and are indicated in the annexed engraving : 
 
 PICTORIAL SECTION OF AEDTUN HEAD. 
 
 1,1. Basalt, rudely columnar. 
 
 2, 2. First leaf-bed. 
 
 3, 3. First tuff-bed. 
 
 4, 4. Second leaf-bed. 
 
 5, 5. Second tuff-bed. 
 
 6, 6. Third leaf-bed. 
 
 7, 7. Amorphous basalt. 
 
 8, 8. Columnar basalt. 
 
 1 . Basalt, having " horizontal divisions and vertical 
 joints," taking the form of rude pillars. The thickness 
 of the basalt is 40 feet. 
 
 2. The first leaf-bed, a thin ueam, about a foot thick, 
 of shaly matter, bearing impressions of leaves and stems 
 of plants. 
 
 3. A bed of volcanic ashes or tuff; being an ashy 
 paste full of white angular fragments or lapilli, disposed 
 in a manner characteristic of erupted volcanic matter, 
 and closely resembling, as I am informed by Sir C. Lyell, 
 similar products found in Mont d'Or in Auvergne. But 
 there is one peculiarity of a remarkable character ; the 
 whole of the beds, although not far removed from the 
 horizontal, dip slightly towards the S.E. or landward end 
 of the ravine ; and in that direction, this bed of tuff passes 
 into a conglomerate of flints, cohering by a cement so 
 tenacious, that the flints themselves frequently break 
 rather than quit their matrix. These flints present, when 
 Avet and freshly broken, the most brilliant tints of red 
 
42 
 
 and orange, and are evidently more or less in a burnt 
 condition. Some of them, however, are less altered than 
 the rest in texture and colour. One specimen I obtained, 
 from external appearance alone was easily identified as 
 an unequivocal chalk flint ; and after I had shown it at 
 the late meeting of the British Association, a fossilised 
 organism was discovered in it, which placed this conclu- 
 sion beyond a doubt. The white lapilli, throughout the 
 whole course of the bed, are generally silicious, although 
 some of the minuter particles have the appearance of 
 unaltered chalk. 
 
 4. The fourth band in the descending order is the 
 second leaf-bed ; that which is by far the richest in 
 vegetable remains. It is about 2 feet thick ; and the 
 lower portion of it is not so much mineral matter with 
 organic impressions, but rather a compressed mass of 
 leaves, not a few of which, when the layers are partly 
 divided, seem still to retain the damp obscure colours of 
 vegetable decay. The composition of the bed becomes 
 harder, as it passes upward, where there is more and more 
 mineral matter, with fewer impressions of plants. These 
 are still, however, frequent, preserving in large and small 
 leaves the most delicate tracery of the skeleton. Some 
 few impressions of twigs are found even above the limits 
 of the bed, and here and there mark the lower portions of 
 the superincumbent tuff. 
 
 5. The fifth bed is a second band of tuff, similar in 
 composition to .the one above described, but somewhat 
 thicker. 
 
 6. The sixth bed is a seam of what may be best de- 
 scribed as baked clay, or very fine mud. It is very 
 brittle, but without any particular form of fracture. 
 From its general appearance and relative position among 
 the beds, it at once suggests itself to be a third leaf-bed. 
 Accordingly, after some search, a few impressions were 
 
43 
 
 obtained of leaves apparently similar in character to those 
 found in the superior deposits. But the nature of the 
 material prevents more than mere fragments being ob- 
 tained. 
 
 7. Below this third and last leaf-bed the cliff is com- 
 posed of a dark basalt, not columnar. Like most of the 
 traps and basalts of the district, it is full of small cavities 
 filled with various mineral crystals. On the surfaces 
 exposed to the action of the air and sea-spray these have 
 decayed out, and the empty holes give here and there a 
 honeycombed appearance to the rock. 
 
 8. Lastly, the cliff ends in beautifully columnar basalt, 
 dipping into the sea. I have not ascertained the sound- 
 ings nor the nature of the bottom, and consequently am 
 unable to say what may be the height of the columns. 
 They may be seen, however, to a considerable depth in the 
 clear waters of that sea. They are sometimes perpen- 
 dicular, sometimes bent in various directions ; a common 
 disposition here being, as at Staffa, a gentle outward 
 curve, as if bending under the weight of the superincum- 
 bent cliff. 
 
 Such are the facts. Let us see what they prove. First, 
 these beds furnish indisputable evidence of volcanic ac- 
 tion, alternating with periods of repose. The second leaf- 
 bed is the one which throws the clearest light on the 
 circumstances of its formation. It is to be observed, 
 that the leaves are not torn or shattered ; those of 
 the large palmated planes, as well as those of the small 
 buckthorn, &c., being fully extended, and showing un- 
 ruffled surfaces. Leaves, violently cast from the trees on 
 which they grew, would not have presented such appear- 
 ances. They do not even consist with the brittleness of 
 dead leaves, when dry. Two other remarkable circum- 
 stances remain to be noticed ; first, that no trunks of trees, 
 no branches, nothing beyond the size of the merest twig, 
 
44 
 
 has been yet found associated with the leaves ; secondly, 
 that plants of a reedy texture some of them at once re- 
 cognisable as Equiseta, plants familiarly known as "Mares' 
 Tales " are associated in great abundance with the 
 leaves, especially with that lower portion of the bed which 
 almost exclusively consists of the vegetable remains. 
 From all this the conclusion is obvious, that these leaves 
 must have been shed, autumn after autumn, into the 
 smooth still waters of some shallow lake, on whose muddy 
 bottom they were accumulated, one above the other, fully 
 expanded and at perfect rest. It cannot have been a 
 water agitated by tides or currents ; for these would have 
 swept such remains away, or left evidence in their dis- 
 position of disturbing agency. It cannot have been water 
 of any depth ; for it is well known that reeds, and espe- 
 cially the Equisetum and other kindred families, do not 
 affect such situations. But there is another ground for 
 this latter conclusion : the bed of ashes or tuff covering 
 the leaves shows clearly, from the arrangement of its 
 materials, that they cannot have undergone the sifting 
 process inseparable from subsidence through water. The 
 light pumiceous particles, and the heavy flinty white 
 lapilli, are disseminated indiscriminately without any 
 reference to the order of gravity, although the former 
 are composed of a substance which will frequently float 
 in water, whilst the latter are particularly dense and 
 heavy. 
 
 All these circumstances taken together, as also the 
 absence of any fresh-water shells, or other organisms, in- 
 dicative of a permanent lacustrine condition, seem to me 
 to afford the strongest evidence that the situation in which 
 these leaves were overflowed by. volcanic mud and ashes, 
 was one which may rather be described as a marshy ter- 
 restrial surface than the bottom of a lake, properly so 
 
45 
 
 called. If this conclusion be correct, it follows that the 
 materials which overlie the leaves were emitted by a 
 volcano throwing out its materials into the open air. 
 The condition of this matter at the time of its erup- 
 tion seems pretty clearly indicated by its condition now. 
 First the damp and bedded leaves have had poured upon 
 them a stream of liquid mud, insinuating itself between 
 their planes, lifting and holding those most easily de- 
 tached from the surface, and leaving in its original state 
 of rest the lower portion of the bed. To this matter 
 which, although now appearing in its upper portion as a 
 hard blue stone, bears, in the perfect state of its vege- 
 table impressions, indisputable evidence of its once liquid 
 condition has succeeded an overflow or a shower of mat- 
 ter of very different composition. In respect to the latter, 
 it is more difficult to conclude with certainty what was the 
 original condition. It seems to have followed the mud 
 after a very short interval of time, although long enough 
 to have allowed a partial consolidation. That stray twigs 
 and leaf-stalks were still sticking out of the surface of the 
 mud, is sufficiently proved by their traces, generally much 
 carbonised, in the lower part of the tuff. The line of 
 junction between the bottom of the tuff and the top of 
 the leaf-bed is, in a general view, sharp and definite 
 enough ; whilst a closer inspection shows just enough 
 subsidence of the particles of ashes into the substance of 
 the stone below to indicate the degree of consolidation to 
 which the latter had attained. 
 
 Whatever may have been the particular process by 
 which the tuff-beds, and this one especially, may have 
 been formed, it is certain that it must have been repeated 
 after a considerable interval of time, and that the volcanic 
 eruption was not of such violence as to change materially 
 the conditions of the surface. The hollow in which the 
 
46 
 
 marsh had originally been formed, and in which the first 
 or lowest leaf-bed had accumulated, continued to be a 
 hollow after the mud and ashes had overflowed it. Water 
 again accumulated, and autumnal leaves were again cast 
 upon its surface in greater numbers and variety than before. 
 An eruption similar to the first for a second time covered 
 its deposits ; still its condition remained sufficiently un- 
 changed to admit a repetition of the same process, and 
 once more it continued to receive the annual sheddings 
 of a forest vegetation. But the third eruption must have 
 been one of a very different kind ; sheets of lava of great 
 solidity and thickness were now poured forth upon the 
 ground. The configuration of the country no longer re- 
 mained the same, and so complete was the change effected 
 by this and subsequent convulsions, that the spot which 
 had so long been the receptacle of calm stagnant waters 
 under the lee of some great forest, became as we now see 
 it, cut into the sea-cliff of a naked headland, so pecu- 
 liarly exposed to the surf of a stormy ocean, as well to 
 deserve the description of its Gaelic name, " the Point of 
 Waves." 
 
 Up to the discovery of these leaf-beds, no vestige had 
 been found in Scotland of any portion of the tertiary or 
 new-life rocks strata representing vast periods of time, 
 and constituting large areas of surface, with high moun- 
 tains, in other regions of the globe. The vegetation 
 which flourished during the middle part of those ages 
 seems to have been luxuriant. Its remains form in many 
 parts of Germany an inferior sort of coal, which is ex- 
 tensively used in that country. The leaves preserved in 
 the Mull Beds, embracing specimens of plane, buckthorn, 
 and yew, have been found to belong to that period, and 
 to bear a close resemblance to fossil leaves found in 
 Styria. But the country on which its forests flourished 
 seems to have entirely disappeared. The volcanoes which 
 
47 
 
 pierced its surface have perished likewise, and nothing 
 now remains but fragments of the lava streams, in 
 
 " the group of islets gay 
 Which guard famed Stafla round." 
 
 How much of the area which is now Scotland how 
 much of its surrounding seas was dry land during that 
 Tertiary age, and bore its forest vegetation, we have no 
 means of knowing. We may be sure that the locality of 
 the Ardtun Beds did not constitute the whole of that 
 ancient land, and that the annual shedding of its autumn 
 leaves was not confined to the spot where alone they 
 have been accidentally preserved. These beds, then, 
 are among the many evidences we have of the tremend- 
 ous changes wrought by the action and reaction of fire 
 and water, through countless ages, on the physical aspect 
 of the earth. They well illustrate the principle of Hut- 
 ton, that there has been established " in the constitution 
 of the globe a power for the interchange of sea and land." 
 
 I have no intention of entering upon the religious diffi- 
 culties which the progress of geological discoveries has 
 been supposed to raise. A large number of them have 
 been overcome ; that is to say, they have been seen to 
 be no real difficulties at all, but to have depended, as in 
 the case of astronomy, on the erroneous principles of in- 
 terpretation which had been applied to the words of 
 Scripture. Such difficulties as remain will, in all proba- 
 bility, receive the same solution ; and thus the progress 
 of truth in one department contributes to its progress in 
 another, for surely no unimportant advantage is attained 
 when new light is cast on the conditions under which 
 the literal terms of Scripture narrative or parable are to 
 be understood. 
 
 It may be well, however, in closing this lecture, to 
 say a few words on the general result of geological 
 science as a whole, and the prevailing impressions which 
 
48 
 
 it leaves upon the mind. And, first, looking outwards, 
 as it were, the first idea which it presents, almost 
 with overpowering force, is Time illimitable lapse 
 of Time. Years cease to measure it ; cycles of ages 
 appear too small a unit with which to number its dura- 
 tion. When we think of it we may repeat, with some 
 nearer approach to an understanding of their meaning, 
 the words of David " In thy sight a thousand years 
 are as yesterday when it is past, and as a watch in the 
 night." The next idea which is brought forcibly before 
 our mind is this that, during that enormous lapse of 
 time, a progressive series of events has been directed to 
 a definite and foreseen result. Here, again, old and fami- 
 liar words seem to bear a new sense to be deeper and 
 truer than we ever knew before : " The sea is His ; and 
 He made it ; and His hands have PREPARED the dry land." 
 What a long preparation that has been ! How many 
 worlds succeeding worlds have been required to produce 
 our existing earth, with its variety of surface and of cli- 
 mate its stores of coal, and lime, and iron the indis- 
 pensable materials of human industry and wealth ! And 
 then, that wonderful history of animal life, in which we 
 see it built up from low beginnings, through the dreadful 
 dragons and monsters of the middle ages of geology to 
 the higher races which now minister to the wants of man ! 
 Of all this, no other word than the word " Prepare " gives 
 the explanation or the meaning ; for it must be always 
 remembered that what are called natural laws are not 
 really explanatory. They define the rules according to 
 which certain effects are produced ; but they do not 
 explain to us either the how or the why. Yet these are 
 the ultimate questions which the human mind is ever 
 asking, and without an answer to which nothing can be 
 fully understood. Because it is in the answer to these 
 questions that we can alone recognise the creating and 
 
49 
 
 directing Will. Causes are not reasons ; but the reason 
 of a thing is its only real explanation to a reasoning mind ; 
 there is nothing intelligible except Intelligence. 
 
 And next looking inwards at ourselves in the light of 
 this science, the first idea that must strike us is that which 
 is first by the mere force of contrast, the almost infinite 
 smallness of our own term of life. " Behold Thou hast 
 made our days as an handbreadth, and our age is as 
 nothing before Thee." But then comes a contrast of 
 another kind a contrast between our littleness in one 
 aspect and our greatness in another. Our desire to know, 
 and our capacities of knowledge, how large and wide they 
 are as compared with our power of finding out ! We can 
 discover, and we have discovered much we seem to see 
 what passed ages before we were born, or our race began. 
 But the deepest and highest truths which we long to know 
 are inaccessible to our researches. At moments we may 
 be beguiled with the hope that we are on the point of 
 seeing something of the mysteries of creation ; but they 
 recede as we advance. The Creator eludes our search. 
 It is as true now as it was in the days of Job " Be- 
 hold I go forward, but He is not there ; and backward, 
 but I cannot perceive Him : on the left hand where He 
 doth work, but I cannot behold Him : He hideth himself 
 on the right hand that I cannot see Him." What, then, 
 is the last and prevailing impression left upon our mind 
 by this general review of the results of science \ What 
 but this, the reasonableness of expecting that those 
 truths which we have faculties impelling us to seek, but 
 no faculties enabling us to discover, should be given to us 
 by direct revelation. Science leads us up to a point where 
 our interest is most excited, and then she drops our hand, 
 intimating that she has reached her goal, and that if we 
 would go farther it must be under another guide. It is 
 thus that Science becomes the vestibule of the Church, 
 
50 
 
 and Knowledge the handmaid of Eeligion. All this, and 
 more than this, is beautifully expressed in that great 
 storehouse of poetic truth and feeling, Tenn}^son's " In 
 Memoriam." Speaking of knowledge or science, he 
 says : 
 
 " Half-grown as yet, a child, and vain 
 She cannot fight the fear of Death. 
 What is she, cut from love and faith, 
 But some wild Pallas from the brain 
 
 Of demons ? fiery hot, to burst 
 All barriers in her onward race 
 For power. Let her know her place ; 
 She is the second, not the first. 
 
 A higher hand must make her mild, 
 If all be not in vain ; and guide 
 Her footsteps, moving side by side 
 With wisdom, like the younger child ! '' 
 
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