[ 262 ] 



formed of flrata, refling upon and intercepted between maffcs 

 of granite or other primitive rocks, at depths in moft places not 

 cafily acceflible. 



2^0. Why the ftrata of fecondary mountains are generally ele- 

 vated in the diredion that faces the next primitive mountains, 

 though frequently diftant from them, being as we have feen ori- 

 ginally formed againft, and along the floping fides of thofe moun- 

 tains, and the feparation occafioned by thecourfe of waters that 

 formed the vallies that intercede between them. The feeming 

 exceptions to this rule arife either from the finking of the primi- 

 tive mountain to which the fecondary faced, as happened to that 

 which flood where the lake of Geneva is now placed, whofe bot- 

 tom is chiefly granite, or fome other primitive rock, as Mr. Sauf- 

 fure attefis, i SaufT. 15, and therefore the elevation of the flrata 

 of the Mole, Saleve, &c. face the lake, Id. p. 222, 223, &c. or 

 becaufe thefe ftratified hills were originally independent, being 

 formed on the fragments of primitive mountains, as already 

 faid. 



Hence alfo we may explain an important obfervation made 

 by Mr. Schreiber on the mountain of Gardette, which confifls of 

 limeftone fuperimpofed on gneifs ; he obferved that where they 

 joined, the gneifs had penetrated into the body of the limeftone, 

 but the limeftone did not penetrate into that of the gneifs, whence 



he 



