£68 



MINERA LOGICAL ACCOUNT 



of greenstone alternate with the sandstone in a 

 very regular manner ; and on the west side of 

 Culliesvoe, it likewise appears to rest upon a bed 

 of compact- felspar, although their relative position 

 is by no means obvious. 



breccia # . 



By this, I mean a rock of angular fragments, 

 cemented by a basis of a different composition. 



* I have employed this word, which is of frequent use, 

 to express an aggregated rock of angular fragments, ce- 

 mented by a basis of a different composition, It differs 

 from Puddingstone, not only in the cement, but in the 

 fragments not being rounded. From Conglomerate, it 

 likewise differs, in the fragments not being the same 

 with the cement. In Zetland, there are three distinct 

 kinds of agglutinated rocks : — The first consists of angular 

 fragments of porphyritic or compact-felspar rocks, ce- 

 mented by a clayey or sandstone basis. It occurs in 

 thin beds. This I have termed Breccia.-— The second is 

 moderately fine-grained sandstone, containing rounded 

 masses of granite, gneiss, and other rocks of the primi- 

 tive class, from the size of an egg, to one or two feet 

 in diameter. These beds are of great thickness. — Last- 

 ly, clayey sandstone, including angular fragments of si- 

 milar composition, the cement and the fragments being 

 the same. This occurs in moderately thin beds, along 

 with fine-grained sandstone. This last kind is, with pro- 

 priety, termed Sandstone-conglomerate ; but the same 

 phrase does not appear so applicable to the second kind, 

 whose imbedded masses claim a very different origin, 



