UNIFORMITY OF CHANGE 427 



There is, therefore, evidence, he says, in Sicily of this revo- 

 lution in the animate world having been effected ' without the 

 intervention of any convulsion or abrupt changes, certain 

 species having from time to time died out, and others having 

 been introduced, until at length the existing fauna was 

 elaborated/ 



In no part of Europe is the absence of all signs of man 

 or his works, in strata of comparatively modern date, more 

 striking than in Sicily. In the central parts of that island 

 we observe a lofty table-land and hills, sometimes rising to 

 the height of 3,000 feet, capped with a limestone, in which 

 from 70 to 85 per cent, of the fossil testacea are specifically 

 identical with those now inhabiting the Mediterranean. 

 These calcareous and other argillaceous strata of the same 

 age are intersected by deep valleys which appear to have been 

 gradually formed by denudation, but have not varied mate- 

 rially in width or depth since Sicily was first colonised by 

 the Greeks. The limestone, moreover, which is of so late a 

 date in geological chronology, was quarried for building 

 those ancient temples of Girgenti and Syracuse, of which the 

 ruins carry us back to a remote era in human history. If 

 we are lost in conjectures when speculating on the ages 

 required to lift up these formations to the height of several 

 thousand feet above the sea, and to excavate the valleys, how 

 much more remote must be the era when the same rocks 

 were gradually formed beneath the waters ! 



The intense cold of the Glacial period was spoken of in 

 the tenth chapter. Although we have not yet succeeded in 

 detecting proofs of the origin of man antecedently to that 

 epoch, we have yet found evidence that most of the testacea, 

 and not a few of the quadrupeds, which preceded, were of 

 the same species as those which followed the extreme cold. 

 To whatever local disturbances this cold may have given rise 

 in the distribution of species, it seems to have done little in 

 effecting their annihilation. We may conclude therefore, 

 from a survey of the tertiary and modern strata, which con- 

 stitute a more complete and unbroken series than rocks 

 of older date, that the extinction and creation of species 

 have been, and are, the result of a slow and gradual change 

 in the organic world. 



