!2gd ON TllE IORMATION OF ROCKt 



y^h 



Saiidstoue, and a much less proportion of slaty clay^ 

 and argil> than the first khid of deposits. 



The thitd kind of repositories or deposits^ are not 

 so regular as the other two, and more difficult to de- 

 fine. They are generally found at the foot of those 

 i^ahges of mountains, where the old red sandstone takes 

 the place of the compact limestone, on the flank of the 

 primitive J such as the coals on the south side of the 

 idbuntains in Bohemia — -along the chain of the Vosges 

 *^parts of those found in the south of France — and in 

 Bcotland. 



TI16 stratiAcatiori of this deposit of coal, is neithei* 

 (extensive nor regular. It is often interrupted and bro- 

 ken, having frequently basalt in its neighbourhood, or 

 the trap formation, which in some places covers it. It 

 is also covered by^ and alternates with, a greater pro- 

 portion of saiidstone; and there are comparatively, per- 

 haps, fewer vegetable impressions, or the remains of or- 

 ganic matter, in the accompanying stratification. 



From all this it may reasonably be concluded, that 

 at the time these coal formations took place^ the sur- 

 face of the earth was partly covered by primitive, part- 

 ly by transition, and partly by secondary rocks, as we 

 find it at present* 



13. Gypsum. This formation sfeems to par- 

 lake of Neptunian origin, by its including the remains 

 of organic matter ; alternating with aggregates of rocks 

 rotihded by attrition, containing shells; and being 

 ifound geherally in a more crystalline form than the 

 other rocks of this class, owing perhaps, to its great 

 solubility iu water 5 it occupies the lower situations^ 



