﻿CXvi PEOCEEDIXGS OP THE GEOLOGICAL SOCIETY. [May I908, 



This essay and the expansion of it in his subsequently published 

 volume, even if all the later criticism of it should be sustained, 

 must still be regarded as having formed, at the time when it was 

 promulgated, perhaps the most momentous generalization that had 

 ever been made, from actual observations, regarding the possible 

 movements of the ocean-bed. In the same year he presented 

 another paper to the Society ' On the Connexion of certain 

 Tolcanic Phenomena in South America, & on the Formation of 

 Mountain-Chains & Volcanoes as the Effects of the same Power 

 by which Continents are Elevated.' ^ In his journeys he had been 

 much impressed with the evidence of extensive uprise on the 

 South American coast, and although he connected this elevatory 

 movement with the volcanic energy so abundantly manifested in the 

 same region, he cautiously refrained from confident deductions, 

 concluding with the following sentence : — 



' The furthest generalisation which the consideration of the Tolcanic pheno- 

 mena described in this paper appears to lead to, is, that the configuration of 

 the fluid surface of the earth's nucleus is subject to some change — its cause 

 completely unknown ; its action slow, intermittent, but irresistible.' 



While dealing with the traces of stupendous movements of the 

 terrestrial crust, Darwin was at the same time engaged upon 

 some of the minuter aspects of geological change. He was 

 watching with scrupulous patience, on some of his pastures in 

 Kent, the action of earthworms in bringing up the finer particles 

 of soil to the surface.^ Xo one had previously thought it worth 

 while to reckon this apparently insignificant action among the 

 geological operations concerned in altering the surface of the land ; 

 and yet Darwin was able to show, by measurement and computation, 

 how appreciable the alteration may be in the course of years. 

 The early studies in this subject which he communicated to the 

 Society were resumed by him forty years afterwards, when his 

 fame as a naturalist had become world-wide, and his essay of 184Q 

 in our Transactions was expanded by him into his volume ' The 

 Pormation of Vegetable Mould through the Action of Worms ' 

 (1881). 



One of the most obvious questions suggested by an examination 

 of the surface of the land is the origin of the valleys by which 

 that surface is diversified. Hutton and Playfair had maintained 



1 Trans, ser. 2, toI. v (1840) p. 601. 



2 * On the Formation of Mould ' ibid. p. 505. 



