3iS 



NA TURE 



[August 4, 1892 



treatise was in many respects an original contribution to 

 science of the highest value. It placed for the first time in the 

 clearest light the whole philosophy of Hutton regarding the his- 

 tory of the earth, and enforced it with a wealth of reasoning and 

 copiousness of illustration which obtained for it a wide apprecia- 

 tion. From long converse with Hutton, and from profound 

 reflection himself, Playfair gained such a comprehension of the 

 whole subject that, discarding the non-essential parts of his 

 master's teaching, he was able to give so lucid and accurate an 

 exposition of the general scheme of Nature's operations on the 

 surface of the globe, that with only slight corrections and expan- 

 sions his treatise may serve as a text-book to-day. In some 

 respects, indeed, his volume was long in advance of its time. 

 Only, for example, within the present generation has the truth 

 of his teaching in regard to the origin of valleys been generally 

 admitted. 



Various causes contributed to retard the progress of the Hut- 

 tonian doctrines. Especially potent was the influence of the 

 teaching of Werner, who, though he perceived that a definite 

 order ot sequence could be recognized among the materials of 

 the earth's crust, had formed singularly narrow conceptions of 

 the great processes whereby that crust has been built up. His 

 enthusiasm, however, fired his disciples with the zeal of 

 proselytes, and they spread themselves over Europe to preach 

 everywhere the artificial system which they had learnt in Saxony. 

 By a curious fate Edinburgh became one of the great head- 

 quarters of Wernerism. The friends and followers of Hutton 

 found themselves attacked in their own city by zealots who, 

 proud of superior mineralogical acquirements, turned their most 

 cherished ideas upside down and assailed them in the uncouth 

 jargon of Freiberg. Inasmuch as subterranean heat had been 

 invoked by Hutton as a force largely instrumental in consoli- 

 dating and upheaving the ancient sediments that now form so 

 great a part of the dry land, his followers were nicknamed 

 Plutonists, On the other hand, as the agency of water was 

 almost alone admitted by Werner, who believed the rocks of the 

 earth's crust to have been chiefly chemical precipitates from a 

 primeval universal ocean, those who adopted his views received 

 the equally descriptive name of Neptunists. The battle of 

 these two contending schools raged fiercely here for some years, 

 and though mainly from the youth, zeal, and energy of Jameson, 

 and the influence which his position as Professor in the Univer- 

 sity gave him, the Wernerian doctrines continued to hold their 

 place, they were eventually abandoned even by Jameson him- 

 self, and the debt due to the memory of Hutton and Playfair 

 was tardily acknowledged. 



The pursuits and the quarrels of philosophers have 

 from early times been a favourite subject of merriment 

 to the outside world. Such a feud as that between the 

 Plutonists and Neptunists would be sure to furnish abun- 

 dant matter for the gratification of this propensity. Turn- 

 ing over the pages of Kay's "Portraits," where so much 

 that was distinctive of Edinburgh's society a hundred years ago 

 is embalmed, we find Hutton's personal peculiarities and pur- 

 suits touched off in good-humoured caricature. In one plate he 

 stands with arms folded and hammer in hand, meditating on the 

 face of a cliff", from which rocky prominences in shape of human 

 faces, perhaps grotesque likenesses of his scientific opponents, 

 grin at him. In another engraving he sits in conclave with his 

 Iriend Black, possibly arranging for that famous banquet of 

 garden-snails which the two worthies had persuaded themselves 

 to look upon as a strangely neglected form of human food. 

 More than a generation later, when the Huttonists and Werner- 

 ists were at the height of their antagonism, the humorous side of 

 the controversy did not escape the notice of the author of 

 •' Waverley," who, you will remember, when he makes Meg 

 Dods recount the various kinds of wise folk brought by Lady 

 Penelope Pennfeather from Edinburgh to St. Ronan's Well, 

 does not forget to include those who "rin uphill and down dale, 

 knapping the chucky-stanes to pieces wi' hammers, like sae 

 mony rt)ad-makers run daft, to see how the warld was made." 



Among the names of the friends and followers of Hutton there 

 is one which on this occasion deserves to be held in especial 

 honour, that of Sir James Hall, of Dunglass. Having accom- 

 panied Hutton in some of his excursions, and having discussed 

 with him the problems presented by the rocks of Scotland, Hall 

 was familiar with the views of his master, and was able to sup- 

 ply him with fresh illustrations of them from different parts of 

 the country. Gifted with remarkable originality and ingenuity, 

 he soon perceived that some of the questions involved in the 



NO. 1 188, VOL. 46] 



theory of the earth could probably be solved by direct physical 

 experiment. Hutton, however, mistrusted any attempt "to 

 judge of the great operations of Nature by merely kindling a fire 

 and looking into the bottom of a little crucible." Out of defer- 

 ence to this prejudice Hall delayed to carry out his intention 

 during Hutton's lifetime. But afterwards he instituted a remark- 

 able series of researches which are memorable in the history of 

 science as the first methodical endeavour to test the value of 

 geological speculation by an appeal to actual experiment. The 

 Neptunists, in ridiculing the Huttonian doctrine that basalt and 

 similar rocks had once been molten, asserted that, had such 

 been their origin, these masses would now be found in the 

 condition of glass or slag. Hall, however, triumphantly vindi- 

 cated his friend's view by proving that basalt could be fused, 

 and thereafter by slow cooling could be made to resume a stony 

 texture. Again, Hutton had asserted that under the vast pres- 

 sures which must be effective deep within the earth's crust, 

 chemical reactions must be powerfully influenced, and that under 

 such conditions even limestone may conceivably be melted with- 

 out losing its carbonic acid. Various specious arguments have 

 been adduced against this proposition, but by an ingeniously de- 

 vised series of experiments. Hall succeeded in converting lime- 

 stone under great pressure into a kind of marble, and even fused 

 it, and found that it then acted vigorously on other rocks. 

 These admirable researches, which laid the foundations of 

 experimental geology, constitute not the least memorable of the 

 services rendered by the Huttonian school to the progress of 

 science. 



Clear as was the insight and sagacious the inferences of these 

 great masters in regard to the history of the globe, their vision 

 was necessarily limited by the comparatively narrow range of 

 ascertained fact which up to their time had been established. 

 They taught men to recognize that the present world is built of 

 the ruins of an earlier one, and they explained with admirable 

 perspicacity the operation of the processes whereby the de- 

 gradation and renovation of land are brought about. But they 

 never dreamed that a long and orderly series of such successive 

 destructions and renewals had taken place, and had left their 

 records in the crust of the earth. They never imagined that 

 from these records it would be possible to establish a deter- 

 minate chronology that could be read everywhere, and applied 

 to the elucidation of the remotest quarter of the globe. It was 

 by the memorable observations and generalizations of William 

 Smith that this vast extension of our knowledge of the past 

 history of the earth become possible. While the Scottish 

 philosophers were building up their theory here. Smith was 

 quietly ascertaining by extended journeys that the stratified 

 rocks of the West of England occur in a definite sequence, and 

 that each well-marked group of them can be discriminated from 

 the others and identified across the country by means of its en- 

 closed organic remains. It is nearly a hundred years since he 

 made known his views, so that by a curious coincidence we may 

 fitly celebrate on this occasion the centenary of William Smith 

 as well as that of James Hutton. No single discovery has ever 

 had a more momentous and far-reaching influence on the pro- 

 gress of a science than that law of organic succession which 

 Smith established. At first it served merely to determine the 

 order of the stratified rocks of England. But it soon proved to 

 possess a world-wide value, for it was found to furnish the key 

 to the structure of the whole stratified crust of the earth. It 

 showed that within that crust lie the chronicles of a long history 

 of plant and animal life upon this planet, it supplied the means 

 of arranging the materials for this history in true chronological 

 sequence, and it thus opened out a magnificent vista through a 

 vast series of ages, each marked by its own distinctive types of 

 organic life, which, in proportion to their antiquity, departed 

 more and more from the aspect of the living world. 



Thus a hundred years ago, by the brilliant theory of Hutton 

 and the fruitful generalization of Smith, tlie study of the earth 

 received in our country the impetus which has given birth to 

 the modern science of geology. 



To review the marvellous progress which this science has 

 made during the first century of its existence would require not 

 one but many hours for adequate treatment. The march of dis- 

 covery has advanced along a multitude of different paths, and 

 the domains of Nature which have been included within the 

 growing territories of human knowledge have been many and 

 ample. Nevertheless, there are certain departments of investi- 

 gation to which we may profitably restrict our attention on the 

 present occasion, and wherein we may see how the leading 



