3CU ON THE FOnMATION OF ROCKS. [July, 



tiitcs the greatest proportion of the Appeniiies from 

 Genoa to beyond Naples. 



In North America it forms the passage between the 

 priuiitive and secondary, along the whole chain of 

 mountains from north-east to south-west, on the west 

 side of the Alleghany ; and as it were lines or sheaths 

 the primitive along the edges of the great basin 

 of the Mississippi, and supports the great seconda- 

 ry calcareous formation, which fills or occupies that 

 basin. 



It conh;titutes part of the mountains of the Crimea; 

 surrounds the primitive mountains of the Hartz ; is 

 found in Wales, and Cumberland, in England,; and it 

 is probable that there are few primitive mountains in 

 Europe, between the latitudes of 50 and 60 degrees, 

 wliich are not covered on one side or the other by this 

 formation. 



Tiie above general observations on the locality, in- 

 cludes the rocks which accompany and alternate with 

 the graywacke shist, such as the clay slate of transi- 

 tion, the various stratification of limestone, sometimes 

 intimately mixed in thin strata, from half an inch to 

 tv\ o inches in thickness, and at other places alternat- 

 ing in powerful beds, forming almost entn^e mountains. 

 Considering the graywacke shist as the most general, 

 and best characterized, of all the members of the tran- 

 sition family, to avoid repetition, it were perhaps as 

 WbU to place the general observai;ions under that head. 



TJie chain of the Ardennes is almost entirely com- 

 posed of this formation, which, on the Rhine, and 

 oilier places, furnishes considerable cjuarries of roof- 

 iiug slaie. 



