PLAN OF MOUNTAIN SYSTEMS. 



and, in fine, the Himalayas, which include the most lofty moun- 

 tains in the world. 



Parallel to the Corsican system are the chains of Syria and Pal- 

 estine. Parallel to that of Monte Yiso, those of Pindus. Parallel 

 to the Thuringenwald are the mountains of Attica and Negropont. 

 Parallel to the C6te d'Or, or perhaps the Hundsruck, are the Altai 

 range, and so on. 



224. In all that has been hitherto explained the mineralogical 

 components of the succession of strata are the only indications 

 which have been given to determine each geological horizon, a 

 term to be understood as indicating that layer of the crust 

 extending generally over the whole globe, which was contempora- 

 neously deposited. If the waters of the oceans and seas of each 

 epoch deposited everywhere a stratum composed of the same ma- 

 terials, and if the waters of no epoch anterior or posterior deposited 

 like strata, then the mineralogical character of each stratum would 

 supply certain indications of its date. But this has not been the 

 case : on the contrary, strata which were incontestably deposited 

 at the same epoch, are often composed in different places of different 

 mineralogical constituents, while, on the other hand, strata of 

 different epochs of deposition are sometimes found to consist of the 

 same mineralogical components. Although, therefore, in a certain 

 general sense, the mineralogical character of the strata, as has 

 been explained, indicates the date of its deposition, yet when we 

 come to define more exactly the successive geological horizons, 

 these mineral characters cease to afford the necessary tests. 



225. The indications which the mineralogical constituents of the 

 strata have thus failed to supply, have happily been obtained from 

 their fossiliferous deposits. From extensive observations, made 

 both in the old and new world, it has been ascertained that in 

 descending from stratum to stratum downwards, a succession of 

 layers of organic remains have been found lodged within definite 

 limits of geological level, the species found in each being almost 

 totally distinct from those found in those above and below it. So, that 

 wherever we find the same organic remains, however different the 

 strata in which they are lodged may be in their mineralogical 

 character, we may conclude with certainty that they are of con- 

 temporaneous deposition. 



226. Each fossiliferous stratum is distinguished from those above 

 and below it, not only by the specific characters of its organic 

 remains but also by its stratigraphic position, and, as we shall 

 presently show, there are clear indications that the deposition of 

 each such stratum, followed the destruction of the organic world 

 by one of those violent convulsions which have been already 

 described. Of these distinct fossiliferous strata twenty -nine 



25 



