UNIFORMITY OP CHANGE 433 



besides that some links of the chain which once existed are 

 now entirely lost and others concealed from view, we have 

 good reason to suspect that it was never complete originally. 



It may undoubtedly be said that strata have been always 

 forming somewhere, and therefore at every moment of past 

 time Nature has added a page to her archives ; but, in refer- 

 ence to this subject, it should be remembered that we can 

 never hope to compile a consecutive history by gathering 

 together monuments which were originally detached and 

 scattered over the globe. For, as the species of organic be- 

 ings contemporaneously inhabiting remote regions are dis- 

 tinct, the fossils of the first of several periods which may be 

 preserved in any one country, as in America for example, 

 will have no connection with those of a second period found 

 in India, and will therefore no more enable us to trace the 

 signs of a gradual change in the living creation, than a 

 fragment of Chinese history will fill up a blank in the polit- 

 ical annals of Europe. 



The absence of any deposits of importance containing 

 recent shells in Chili, or anywhere on the western coast of 

 South America, naturally led Mr. Darwin to the conclusion 

 that ' where the bed of the sea is either stationary or rising, 

 circumstances are far less favourable than where the level is 

 sinking to the accumulation of conchiferous strata of 

 sufficient thickness and extension to resist the average vast 

 amount of denudation." In like manner the beds of super- 

 ficial sand, clay, and gravel, with recent shells, on the coasts 

 of Norway and Sweden, where the land has risen in Post- 

 tertiary times, are so thin and scanty as to incline us to 

 admit a similar proposition. We may in fact assume that 

 in all cases where the bottom of the sea has been undergoing 

 continuous elevation, the total thickness of sedimentary 

 matter accumulating at depths suited to the habitation of 

 most of the species of shells can never be great, nor can the 

 deposits be thickly covered by superincumbent matter, so as 

 to be consolidated by pressure. When they are upheaved, 

 therefore, the waves on the beach will bear down and dis- 

 perse the loose materials; whereas, if the bed of the sea 

 subsides slowly, a mass of strata, containing abundance of 



Darwin's S. America, pp. 136, 139. 



