558 



N.4 TURE 



[August 8, 1907 



science. Its object was to apply to Geology one particular 

 mode of research. It adopted as its motto this fine passage 

 from Bacon : — 



" If any man makes it his delight and care — not so 

 much to cling to and use past discoveries, as lo penetrate 

 to what is beyond them — not to conquer Nature by talk, 

 but by toil — in short, not to have elegant and plausible 

 theories, but to gain sure and demonstrable knowledge ; 

 let such men (if it shall seem to them right), as' true 

 children of knowledge, unite themselves with us." 



The methods of the society were as practical as its 

 ideals. London, with characteristic unconventionality and 

 originality, has used its scientific societies as its university 

 for post-graduate teaching. Informally the Geological 

 Society enrolled every British master of Geology on its 

 staff of unpaid professors, then set each of them to teach 

 the branch of Geology which he knew best. .\nd these 

 professors were no carpet knights ; they were knights 

 errant who derived their kncw'ledge, not from books alone, 

 but from their wanderings over hills and dales, in mines 

 and quarries, by ice-polished rocks and water-worn valleys, 

 .^t its meetings the leaders of the society announced what 

 they had discovered, gave sure and demonstrable proofs 

 of their discoveries, and showed in w'hat direction the 

 geological forces should be directed for the conquest of 

 Nature. The goodly fellowship of the Geological .Society 

 has alw^ays encamped on the ever-advancing frontier of 

 geological knowledge, w'hcre the well-surveyed tracks pass 

 out into the bright, alluring realms of the unknown. 



The actual founders of the Geological Society were 

 apparently men of less showw intellect than the great 

 Werner, whose teaching had intoxicated many of the most 

 gifted of his enthusiastic pupils. They were men, like 

 Horner and Greenough, who had a practical insight that 

 enabled them to give a permanent help to the progress 

 of science. They had that supreme gift, the power to 

 see things as they are. It would not be fair to claim 

 for them that they were the originators of accurate 

 methods in Geology : such methods had been used before 

 their day — by William Smith in England, by Lehman in 

 Germany, and by Desmarest in France. But these men, 

 acting singly, had not been able to save Geology from the 

 eighteenth-century spirit of adventurous speculation, nor 

 had they lifted from Geology the burden of those quaint 

 theories, that made this science the butt of \'oltaire's 

 luminous ridicule. 



The great achievement of the Geological Society has 

 been this : as a corporate body it has been able to spread 

 its influence very widely ; its clear-sighted pursuit of a 

 practical ideal has been adopted in other countries ; its 

 resolute rejection of the temptation to wander in dream- 

 land has affected geological students all over the world. 

 In this way has been laid a broad foundation of positive 

 knowledge upon which modern Geology has been built. 



The fine self-restraint, which induced the founders of 

 the Geological Society to restrict its work for a while to 

 observing the surface of the earth, has haif its reward. 

 The methods this society was founded to employ have 

 been so widely used, that we now have geological maps 

 of a wider area than was known to geographers of a 

 century ago. The general distribution of all the rocks on 

 the earth's surface has been discovered ; most settled 

 countries have been surveyed in some detail ; the main 

 outlines of the history of life on the earth have been 

 written and carried back almost as far as palaeontologists 

 are likely to go. There are doubtless fossiliferous areas 

 still undiscovered in the " back blocks " of the world ; but, 

 though negative predictions are proverbially reckless, it 

 seems probable that Palfeontology will not carry geological 

 history materially farther back. Fossils have been dis- 

 covered in the pr£E-Cambrian rocks ; the best known is 

 the fauna described by Walcot from Montana ; but his 

 Beltina, the oldest well-characterised fossil, is still of 

 Palncozoic type. It may be that the poverty of carbonate 

 ot lime, which Is so characteristic a feature of most 

 Cambrian and pr^-Cambrian sediments, indicates that the 

 bulk of the contemporary organisms had chitinous shells 

 or were soft-bodied. Palaeontology begins with the appear- 

 ance of hard-bodied organisms ; it can only reveal to us 

 the dawn of skeletons, not the dawn of life. We are 



dependent for knowledge of the climate and geography of 

 Eozoic time to the evidence of the sediments, of which 

 there are great thicknesses beneath the fossiliferous rocks 

 in most parts of the world.' 



II. The Geology of the Inner Earth. 



Now that this geological survey of the earth is in rapid 

 progress ; while the history of life has been written at 

 least in outline ; the chief fossils, minerals, and rocks have 

 been described and generously endowed with names ; and 

 the manifold activity of water and air in moulding the 

 surface is duly appreciated, it is not surprising to find 

 that the centre of geological interest is shifting to the 

 deeper regions of the earth's crust and to the problems of 

 applied Geology. The secrets of these deeper regions are 

 both of scientific and economic interest. They are of 

 scientific importance, for it is now generally recognised 

 that the main plan of the earth's geography and the 

 essential characters of the successive geological systems 

 are the result of internal movements. The relative import- 

 ance of those restless external agents that we can watch, 

 denuding here and depositing there, has been exaggerated ; 

 probably they do little more than soften the outlines due 

 to the silent heavings produced by the colossal energies 

 of the inner earth. 



The study of the deeper layers of the crust is of 

 economic interest, for, with keener competition between 

 increasing populations and with the exhaustion of the 

 most easily used resources of field and mine, there is 

 growing need for the better utilisation of soils and waters, 

 and for the pursuit of deeper deposits of ore. 



If a shaft be sunk at any point on the earth's surface, 

 a formation of Archaean schists and gneisses would prob- 

 ably always be reached ; and, working backward, geo- 

 logical methods always fail at last — in primaeval, Archaean 

 darkness. The .Archaean rocks still hide from us the 

 earlier period of the earth's history, including that of alt 

 rocks which now lie beneath them. But already there 

 are indications that the mystery of the " beyond " is not 

 so impenetrable as it seemed. 



(i) The Nchiilar , niirf Mefeoritic Hypotheses.— The 

 eighteenth century explained the history of the earth by 

 the nebular hypothesis of Laplace. Geologists respect- 

 fully adopted ttiis idea from the astronomers ; they acceptecf 

 it as one of those essential facts of the universe with 

 which geological philosophy must harmonise. The result- 

 ing theory represented the earth as originally a glowing 

 cloud of incandescent gas, which slowly cooled, until an 

 irregular crust of rock formed around a gaseous or molten 

 core ; as the surface grew cooler, the depressions in the 

 crust were filled with water from the condensing vapour, 

 forming oceans which became habitable as the temperature 

 further fell. The whole earth was thought to have had 

 a long period with a universal tropical climate, under 

 which corn! reefs grew where flow our polar seas, and 

 palms flourished on what are now the -Arctic shores. Stilt 

 further cooling had established our climatic zones ; and 

 it was predicted that in time the polar cold would creep 

 outward, driving all living beings toward the equator, 

 until at length the whole earth, like the moon, would 

 become lifeless through cold, as it had once been un- 

 inhabitable through heat. This theory has permanently 

 impressed itself on geological terminology : and its 

 corollaries, secular refrigeration and the contortion of the 

 shrinking crust, once dominated discussions concerning 

 climatic history and the formation of mountain chains. 

 This nebular hypothesis, however, we are now told, is 

 mathematically improbable, or even impossible : and it is 

 only consistent with the facts of Geology on the assump- 

 tion that, in proportion to the age of the world, the whole 

 of geological time is so insignificant that the secular 

 refrigeration during it is quite inappreciable; hence 

 Geology can no more confirm or correct the theory than 

 a stockbreeder could refute evolution by failing to breed' 

 kangaroos into cows in a single lifetime. 



The theory of the gaseous nebula has been probably of 



1 Such are ihe Aleon'dan sediments represented by the Huronian and 

 AlpnnVians of Amerira. the A'ffonkians of Scandinavia, the Karelian nf Fin- 

 land the Rtiovarlan of Nonh-Wesl Fra"ce, the Healhcotian "f Australia, 

 the Transvaal and "^u^a^-iland sysi..ms nf South Africa, the Dharwar and 

 Bijawar systeins of India, the Itacolumnite series of Brazil, &c. 



NO. 1971, VOL. 76] 



