THEORY OP THE EARTH. 41 



. 



Yet, amidst all this confusion, some naturalists 

 have thought that they perceived a certain degree 

 of order prevailing, and that among these immense 

 beds of rocks, broken and overturned though they 

 be, a regular succession is observed, which is near- 

 ly the same in all the different chains of mountains. 

 According to them, the granite, which surmounts 

 every other rock, also dips under every other rock ; 

 and is the most ancient of any that has yet been dis- 

 covered in the place assigned it by nature. The 

 central ridges of most of the mountain chains are 

 composed of it; slaty rocks, such as clay slate, 

 granular quartz, (gres^) and mica slate, rest upon 

 its sides and . form lateral chains ; granular, folia- 

 ted limestone, or marble, and other calcarious 

 rocks that do not contain shells, rest upon the slate, 

 forming the exterior ranges, and are the last forma- 

 tions by which this ancient uninhabited sea seems 

 to have prepared itself for the production of its 

 beds of shells.*! 



O-Vi--;,' '"''' 



On all occasions, even in districts that lie at a 

 distance from the great mountain chains, where 

 the more recent strata have been digged through, 

 and the external covering of the earth penetrated 

 to a considerable depth, nearly the same order of 

 stratification has been found as that already de- 

 scribed. The crystallized marbles never cover 



* See Pallas, in his Memoir on tlie Formation of Mountains?, 

 t Note B. 



6 



