August 4, 1892] 



NATURE 



19 



principles that were proclaimed in this city a hundred years ago 

 have germinated and borne fruit ail over the world. 



From the earliest times the natural features of the earth's 

 surface have arrested the attention of mankind. The rugged 

 mountain, the cleft ravine, the scarped cliflF, the solitary 

 boulder, have stimulated curiosity and prompted many a specu- 

 lation as to their origin. The shells embedded by millions in 

 the solid rocks of hills far removed from the sea have still 

 further pi essed home these " obstinate questionings." But for 

 many long centuries the advance of inquiry into such matters 

 was arrested by the paramount influence of orthodox theology. 

 It was not merely that the Church opposed itself to the simple 

 and obvious interpretation of these natural phenomena. So im- 

 plicit had faith become in the accepted views of the earth's age 

 and of the history of creation, that even laymen of intelligence 

 and learning set themselves unbidden and in perfect good faith 

 to explain away the difficulties which Nature so persistently 

 raised up, and to reconcile her teachings with those of the 

 theologians. Jn the various theories thus originating, the 

 amount of knowledge of natural law usually stood in inverse ratio 

 to the share played in them by an uncontrolled imagination. The 

 speculations, for example, of Burnet, Whiston, Whitehurst, and 

 others in this cuntry, cannot be read now without a smile. In 

 no sense were they scientific researches ; they can only be looked 

 upon as exercitations of learned ignorance. Springing 

 mainly out of a laudable desire to promote what was believed 

 to be the cau<e of true religion, they helped to retard inquiry, 

 and exercised in that respect a baneful influence on intellectual 

 progress. 



It is the special glory of the Edinburgh school of geology to 

 have cast aside all this fanciful trifling. Hutton boldly pro- 

 claimed that it was no part of his philosophy to account for the 

 beginning of things. His concern lay only with the evidence 

 furnished by the earth itself as to its origin. With the intuition 

 of true genius he early perceived that the only solid basis from 

 which to explore what has taken place in byegone time is a 

 knowledge of what is taking place to-day. He thus founded 

 his sy.-tem upon a careful study of the processes whereby geolo- 

 gical changes are now brought about. He felt assured that 

 Nature must be consistent and uniform in her working, and 

 that only in proportion as her operations at the present time are 

 watched and understood will the ancient history of the earth 

 become intelligible. Thus, in his hands, the investigation of 

 the Present became the key to the interpretation of the Past. 

 The establishment of this great truth was the first step towards 

 the inauguration of a true science of the earth. The doctrine of 

 the uniformity of causation in Nature became the fruitful prin- 

 ciple on which the structure of modern geology could be 

 built up. 



Fresh life was now breathed into the study of the earth. A 

 new spirit seemed to animate the advance along every pathway 

 of inquiry. Facts that had long been familiar came to possess a 

 wider and deeper meaning when their connection with each 

 other was recognized as parts of one great harmonious system of 

 continuous change. In no department of Nature, for example, 

 was this broader vision more remarkably displayed than in that 

 wherein the circulation of water between land and sea plays the 

 most conspicuous part. From the earliest times men had 

 watched the coming of clouds, the fall of rain, the flow of rivers, 

 and had recognized that on this nicely adjusted machinery the 

 beauty and fertility of the land depend. But they now learnt 

 that this beauty and fertility involve a continual decay of the 

 terrestrial surface ; that the soil is a measure of this decay, and 

 would cease to aff"ord us maintenance were it not continually 

 removed and renewed ; that through the ceaseless transport of 

 soil by livers to the sea the lace of the land is slowly lowered in 

 level and carved into mountain and valley, and that the mate- 

 rials thus borne outwards to the floor of the ocean are not lost, 

 but accumulate there to form rocks, which in the end will be 

 upraised into new lands. Decay and renovation, in well- 

 balanced proportions, were thus shown to be the system on 

 which the existence of the earth as a habitable globe had been 

 established. It was impos.iible to conceive that the economy of 

 the planet could be maintained on any other basis. Without 

 the circulation of water the life of plants and animals would be 

 impossible, and with that circulation the decay of the surface of 

 the land and the renovation of its disintegrated materials are 

 necessarily involved. 



As it is now so must it have been in past time. Hutton and 

 Playfair pointed to the stratified rocks of the earth's crust as 



NO. 1 188, VOL. 46] 



demonstrations that the same processes which are at work to-day 

 have been in operation from a remote antiquity. By thus 

 placing their theory on a basis of actual observation, and provi- 

 diiig in the study of existing operations a guide to the interpre- 

 tation of those in past times, they rescued the investigation of 

 the history of the earth from the speculations of theologians and 

 cosmologists, and established a place for it among the recog- 

 nized inductive sciences. To the guiding influence of their 

 philosophical system the prodigious strides made by modern 

 geology are in large measure to be attributed. And here in 

 their own city, after the lapse of a hundred years, let us offer 

 to their memory the grateful homage of all who have profited by 

 their labours. 



But while we recognize with admiration the far-reaching in- 

 fluence of the doctrine of uniformity of causation in the investi- 

 gation of the history of the earth, we must upon reflection admit 

 that the doctrine has been pushed to an extreme perhaps not 

 contemplated by its original founders. To take the existing 

 conditions of Nature as a platform of actual knowledge from 

 which to start in an inquiry into former conditions was logical 

 and prudent. Obviously, however, human experience, in the 

 few centuries during which attention has been turned to such 

 subjects, has been too brief to warrant any dogmatic assumption 

 that the various natural processes must have been carried on in 

 the past with the same energy and at the same rate as they are 

 carried on now. Variations in energy might have been legi- 

 timately conceded as possible, though not to be allowed without 

 reasonable proof in their favour. It was right to refuse to admit 

 the operation of speculative causes of change when the pheno- 

 mena were capable of natural and adequate explanation by 

 reference to causes that can be watched and investigated. But 

 it was an error to take for granted that no other kind of process 

 or influence, nor any variation in the ra'e of activity save those 

 of which man has had actual cognizance, has played a part in 

 the terrestrial economy. The uniformitarian writers laid them- 

 selves open to the charge of maintaining a kind of perpetual 

 motion in the machinery of Nature. 1 hey could find in the 

 records of the earth's history no evidence of a beginning, no 

 prospect of an end. They saw that many successive renovations 

 and destructions had been effected on the earth's surface, and 

 that this long line of vicissitudes formed a series of which the 

 earliest were lost in antiquity, while the latest were still in pro- 

 gress towards an apparently illimitable future. 



The discoveries of William Smith, had they been adequately 

 understood, would have been seen to offer a corrective to this 

 rigidly uniformitarian conception, for they revealed that the 

 crust of the earth contains the long record of an unmistakable 

 order of progression in organic types. They proved that plants 

 and animals have varied widely in successive periods of the 

 earth's history, the present condition of organic life being only 

 the latest phase of a long preceding series, each stage of which 

 recedes further from the existing aspect of things as we trace it 

 backward into the past. And though no relic had yet been 

 found, or indeed was ever likely to be found, of the first living 

 things that appeared upon the earth's surface, the manifest 

 simplification of types in the older formations pointed irresistibly 

 to some beginning from which the long procession had taken its 

 start. If then it could thus be demonstrated that there had been 

 upon the globe an orderly march of living forms from the lowliest 

 grades in early times to man himself to day, and thus that in one 

 department of her domain, extendingthrough the greater portion 

 of the records of the earth's history. Nature had not been uniform 

 but had followed a vast and noble plan of evolution, surely it 

 might have been expected that those who discovered and made 

 known this plan would seek to ascertain whether some analogous 

 physical progression from a definite beginning might not be dis- 

 cernible in the framework of the globe itself. 



But the early masters of the science laboured under two great 

 disadvantaees. In the first place, they found the oldest records 

 of the earth's history so broken up and effaced as to be no longer 

 legible. And in the second place, they lived under the spell 

 of that strong reaction against speculation which followed the 

 bitter controversy between the Neptunists and Piutonists in the 

 earlier decades of the century. They considered themselves 

 bound to search for facts, not to build up theories ; and as in 

 the crust of the earth they could find no facts which threw any 

 light upon the primeval constitution and subsequent develop- 

 ment of our planet, they shut their ears to any theoretical inter- 

 pretations that might be offered from other departments of 

 science. It was enough for them to maintain, as Hutton had 



