286 CHLORITE SCHIST. 



deposit is visible ; except, that in no instance as 

 yet, within my observation, it has been found to 

 contain fragments of other rocks. Where the tex- 

 ture assimilates to that of gneiss, it presents simi- 

 lar undulation, or roughness, in the parallel frac- 

 ture ; is more or less coarsely granular in the trans- 

 verse, and is often undistinguishable from it with- 

 out a careful examination. 



The textures of those varieties which approxi- 

 mate in character to the coarse and fine argilla- 

 ceous schists, or to graywacke and clay slate, are 

 in every respect the same as those which occur in 

 these rocks. In the first, the grains of quartz 

 seem to form a mechanical rather than a chemical 

 assemblage ; varying much in the magnitude of 

 the parts, often bearing the apparent marks of 

 previous attrition, and being also separated in 

 laminae more or less distinct, by the intervening 

 chlorite. As in those varieties of micaceous 

 schist which present a similar character, this sand 

 or gravel of quartz, not unusually possesses an 

 average general size, whether large or small, in 

 one bed ; and the union produced by the smallest 

 admissible quantity of eWorite, Thws Ihe trans- 



