148 



GEOLOGY 



the primary rocks were formed by the cooling of 

 the surface, which also produced the primeval 

 ocean by condensing the surrounding vapours. 

 The sedimentary strata resulted from the subsiding 

 of the waters which had been put in motion by the 

 collapse of the crust on the contracting nucleus. 

 The process was several times repeated until at 

 last equilibrium was established. 



Hooke (1688) and Ray (1690) considered the 

 essential condition of the globe to be one of change, 

 and that the forces now in action would, if allowed 

 sufficient time, produce changes as great as those 

 of geological date. In Italy, Vallisneri (1720), 

 Lazzaro Moro (1740), and his illustrator, Cirillo 

 Generelli, taught that there had been depressions 

 of the land, during which marine fossiliferous strata 

 were deposited, and that subsequently the sea- 

 bottom had been elevated by the subterranean 

 forces, and converted into dry land. Moro main- 

 tained the impossibility of the whole earth having 

 been covered by the waters of the sea up to the tops 

 of the highest mountains. The continents, he 

 said, had been upheaved, and the fractures and 

 dislocations of the strata were pointed to in con- 

 firmation of this view. Generelli insisted upon the 

 gradual degradation of the land by running water, 

 and held that the waste was so great that event- 

 ually the mountains must be washed down to the 

 sea. This inevitable degradation of the surface, 

 however, would be counterbalanced, he inferred, by 

 elevation of the land elsewhere. But as Italian 

 geologists, in common with those of other countries, 

 believed that the world was only some 6000 years 

 old, Moro and Generelli found some difficulty in 

 explaining how so many thousands of feet of strata 

 could have been accumulated within the limited 

 period allowed by the orthodox chronology. They 

 suggested, therefore, that the materials entering 

 into the formation of the strata had been largely 

 derived from volcanic eruptions. 



Eventually the more advanced views held in 

 Italy spread into France, Germany, and England. 

 Buffon (1749), by the publication of his Theory of 

 the Earth, evoked a spirit of inquiry in France ; 

 Lehmann (1756), Fuchsel (1762), and others in 

 Germany did much to establish more correct methods 

 of observation and interpretation of geological 

 phenomena than had hitherto prevailed ; while in 

 England a distinct advance was made by Michell 

 (1760) in his essay on the Cause and Phenomena of 

 Earthquakes. The next name that comes into pro- 

 minence is that of Werner, professor of Mineralogy 

 at Freiburg in Saxony (1775). This celebrated 

 writer framed a classification or system of the rocks 

 of the Harz Mountains, in the order of their 

 succession, and consequently in that of their for- 

 mation, and maintained that this order would be 

 found to prevail generally throughout the world. 

 Werner's classification has proved inadequate, and 

 even in many respects erroneous. Nevertheless, to 

 him belongs the great merit of having brought into 

 prominence a definite principle in the construction 

 of the earth's crust, and a precise method of geo- 

 logical investigation. This discovery of the fact 

 that strata occur in a certain order of superposition 

 had been anticipated by several Italian geologists, 

 and by Lehmann in Germany, but Werner's fame 

 as a brilliant investigator and attractive teacher 

 overshadowed and eclipsed the most of his pre- 

 decessors. In some respects the views of this 

 eminent man were retrograde. He maintained, for 

 example, that his ' formations ' were universal, and 

 had been precipitated over the whole earth in 

 succession, from a common menstruum or chaotic 

 fluid. The igneous rocks, according to him, were 

 chemical precipitates from water ; he believed that 

 no volcanoes existed in the earlier ages of the world, 

 but that volcanic action was exclusively of modern 



date. Yet the true nature of igneous rocks had 

 already been recognised in Italy, France, England, 

 and Germany. With the publication of Werner's 

 views on this subject a great controversy began, 

 which was carried on with an acrimony that 

 is now hard to realise. Those who upheld the 

 igneous origin of such rocks as basalt were styled 

 Vulcanists, while those who followed Werner 

 became known as Neptunists. The great apostle 

 of Vulcanism in Britain was James Hutton ( 1788). 

 He not only insisted upon the igneous nature 

 of basalt rocks but demonstrated in the field 

 that granite likewise was of igneous origin. 

 This philosophical thinker deprecated the calling- 

 in of hypothetical causes to explain geological 

 phenomena. The only agents of change, according 

 to him, were those which are now at work in 

 modifying the earth's crust. The past, therefore, 

 was to be interpreted through the present. It was 

 only through our knowledge of the methods em- 

 ployed by nature in carrying on her operations in 

 our own day that we could hope to interpret the 

 record of the rocks. The Huttonian theory was 

 fortunate in having for its expounder John Play- 

 fair, whose famous Illustrations (1802) has long 

 been held in the highest esteem, and is still 

 studied by geologists. Another friend and dis- 

 ciple of Hutton, Sir J. Hall, became the founder 

 of experimental geology, and did much towards 

 the establishment of the cardinal doctrines of his 

 teacher. Hutton's observations were confined to 

 Scotland, in which fossiliferous strata are not 

 prominently developed. It was the igneous masses 

 the crumpled and shattered rocks of mountain 

 and glen and sea-coast, and the never-absent 

 evidence of denudation and decay that fascinated 

 him. He saw ' the ruins of an older world in the 

 present structure of the globe,' but he knew nothing 

 of that long succession of ruined worlds, each 

 characterised by its own life-forms, with which 

 William Smith (1790) was shortly to astonish geo- 

 logists. This able investigator alone and unaided 

 had explored all England on foot, and succeeded 

 in completing a geological map of the country on 

 which the strata were for the first time delineated 

 and thrown into natural divisions. His views as to 

 the law of superposition among strata were arrived 

 at independently of Werner, and he was the first 

 to point out how each rock -group was distinguished 

 by its own peculiar fossils. Hence Smith is justly 

 entitled to be called the founder of historical or 

 stratigraphical geology. Since then the progress 

 of geology has been rapid. Fossils which at first 

 were valued chiefly as marks by which one forma- 

 tion could be distinguished from another by-and- 

 by claimed fuller attention the classic researches 

 of Cuvier in the Paris basin forming a great epoch 

 in Palaeontology ( q. v. ), or the study of fossil organic 

 remains. 



In closing these remarks on the history of the 

 geological sciences, it would be unjust to omit 

 the name of Lyell, whose great Principles of 

 Geology (1830-33) did invaluable service. His 

 labours were based on. those of Hutton and Play- 

 fair, but he carried out their doctrines further in 

 some directions than either of these geologists Avere 

 prepared to go, while in other directions he did not 

 advance so far. Before the appearance of Ly ell's 

 well-known work, the Huttonian philosophy had 

 conspicuously triumphed, but geologists were still 

 prone to account for what appeared to be ' breaks 

 in the succession ' by the hypothesis of vast catas- 

 trophes. They conceived the possibility of world- 

 wide destruction of floras and faunas, and the 

 sudden introduction or creation of new forms of 

 life, after the forces of nature had sunk into re- 

 pose. The full meaning of denudation had not as 

 yet been generally appreciated, and subterranean 



