DARWIR AND HUMBOLDT, 



[313] 



■eminently characteristic of the writer, 

 and in the finished work the same 

 faculties enriched with the experience 

 of a long and busy life. In bringing 

 to light the operations of the earth- 

 worm, he called the attention of 

 geologists to an agency, the real 

 efficiency of which they probably do 

 not yet appreciate. Elie de Beau- 

 mont looked upon the layer of grass- 

 covered soil as a permanent datum- 

 line from which th*j denudation of ex- 

 posed surfaces might be measured. 

 But, as Darwin showed, the constant 

 transference of soil from beneath to 

 the surface, and the consequent ex- 

 posure of the materials so transferred 

 to be dried and blown away by wind, 

 or to be washed to lower levels by 

 rain, must tend slowly but certainly 

 to lower the level even of undisturbed 

 grass-covered land. 



To another of his early papers ref- 

 erence may be made, from its interest 

 in the history of British geology. 

 Buckland, following in the footsteps 

 ■of Agassiz, had initiated that prodig- 

 ious amount of literature which has 

 now been devoted to the records of 

 the Glacial period in this country, by 

 reading to the Geological Society a 

 paper " On Diluvio-glacial Phenome- 

 na in Snowdonia and in adjacent 

 parts of North Wales " (1841 ). Dar- 

 win, whose wanderings in South 

 American had led him to study the 

 problems presented by erratic blocks, 

 took an early opportunity of visiting 

 the Welsh district described by Buck- 

 land, and at once declared himself to 

 be a believer in the former presence 

 of glaciers in Britain. His paper 

 (1843) in which this belief is stated 

 .and enforced by additional observa- 

 tions, stands almost at the top of the 

 long list of English contributions to 

 the history of the Ice Age. 



The influence exercised upon the 

 progress of geology by Darwin's 

 researches in other than geological 

 fields, is less easy to be appraised. 

 Yet it has been far more widespread 

 and profound than that of his direct 

 geological work. Even as far back 

 as the time of the voyage of the 



Beagle, he had been led to reflect 

 deeply on some of Lyell's specula- 

 tions upon the influence of geological 

 changes on the geographical distribu- 

 tion of animals. From that time the 

 intimate connection between geologi- 

 cal history and biological progress 

 seems to have been continually pre- 

 sent in his mind. It was not, how- 

 ever, until the appearance of the 

 Origin of Species in 1859 that the 

 full import of his reflections was per- 

 ceived. His chapter on the " Imper- 

 fection of the Geological Record " 

 startled geologists as from a profound 

 slumber. It would be incorrect to 

 say that he was the first to recognize 

 the incompleteness of the record; but 

 certainly until the appearance of that 

 famous chapter the general body of 

 geologists was blissfully unconscious 

 of the essentially fragmentary char- 

 acter of the geological record. Dar- 

 win showed why this must necessarily 

 be the case ; how multitudes of organ- 

 ic types, both of the sea and of the 

 land, must have decayed and never 

 have been preserved in any geologi- 

 cal deposit ; how, even if entombed in 

 such accumulations, they would in 

 great measure be dissolved away 

 by the subsequent percolation of water. 

 Returning to some of his early specu- 

 lations, he pointed out that massive 

 geological deposits rich in fossils 

 could only have been laid down dur- 

 ing subsidence, and only where the 

 supply of sediment was sufficient to 

 let the sea remain > shallow, and to 

 entomb the organic remains on its 

 floor before they had decayed. Hence, 

 by the very conditions of its forma- 

 tion, the geological record, instead of 

 being a continuous and tolerably 

 complete chronicle, must be intermit- 

 tent and fragmentary. The sudden 

 appearance of whole groups of allied 

 species of fossils on certain horizons 

 had been assumed by some eminent 

 authorities as a fatal objection to any 

 doctrine of the transmutation of 

 species. But Darwin now claimed 

 this fact as only another evidence of 

 the enormous gaps in geological 

 history. Reiterating again and again 



