Ch. XIIL] CAVE BKECCIAS. 195 



required for the gradual upheaval of the rocks, and the excavation of the 

 valleys. The historical period seems scarcely to form an appreciable unit 

 in this computation, for we find ancient Greek temples, like those of 

 Girgenti (Agrigentum), built of the modern limestone of which we are 

 speaking, and resting on a hill composed of the same ; the site having 

 remained to all appearance unaltered since the Greeks first colonized the 

 island. 



The modern geological date of the rocks in this region leads to another 

 singular and unexpected conclusion, namely, that the fauna and flora of 

 a large part of Sicily are of higher antiquity than the country itself, 

 having not only flourished before the lands were raised from the deep, 

 but even before their materials were brought together beneath the waters. 

 The chain of reasoning which conducts us to this opinion may be stated 

 in a few words. The larger part of the island has been converted from 

 sea into land since the Mediterranean was peopled with nearly all the 

 living species of testacea and zoophytes. We may therefore presume 

 that, before this region emerged, the same land and river shells, and 

 almost all the same animals and plants, were in existence which now 

 people Sicily ; for the terrestrial faima and flora of this island are pre- 

 cisely the same as that of other lands surrounding the Mediterranean. 

 There appear to be no peculiar or indigenous species, and those which 

 are now established there must be supposed to have migrated from j)re- 

 existing lands, just as the plants and animals of the Neapolitan territory 

 have colonized Monte Nuovo, since that volcanic cone was thrown up in 

 the sixteenth century. 



Such conclusions throw a new light on the adaptation of the attributes 

 and migratory habits of animals and plants to the changes which are un- 

 ceasingly in progress in the physical geography of the globe. It is clear 

 that the duration of species is so great, that they are destined to outlive 

 many important revolutions in the configuration of the earth's surface ; 

 and hence those innumerable contrivances for enabling the subjects of the 

 animal and vegetable creation to extend their range ; the inhabitants of 

 the land being often carried across the ocean, and the aquatic tribes over 

 great continental spaces. It is obviously expedient that the terrestrial and 

 fluviatile species should not only be fitted for the rivers, valleys, plains, 

 and mountains which exist at the era of their creation, but for others that 

 are destined to be formed before the species shall become extinct ; and, 

 in like manner, the marine species are not only made for the deep and 

 shallow regions of the ocean existing at the time when they are called 

 iDto being, but for tracts that may be submerged or variously altered in 

 depth during the time that is allotted for their continuance on the 

 globe. * 



* The three last pages, on " The Xewer Pliocene Strata of Sicily," are given 

 verbatim as they appeared thirty years ago in the first edition of the Principles 

 of Geology (vol. hi. p. 115, 1833). The last sentence, marked with inverted com- 

 mas, was couched in language implying my adherence to the theory that each spe- 

 cies was originally created such as it now exists, and was incapable of varying so aa 



