118 THE STRUCTURE OF THE PRIMARY ROCKS. [Ch. VI. 



numerous beds of quartz : throughout this rock appear, in 

 every direction, considerable pieces of gneiss in which the 

 felspar predominates, the mica being only in isolated folia, 

 and the quartz in very small quantity. The mica in these 

 pieces only gives rise to straight and parallel streaks, while in 

 the surrounding gneiss it renders the slaty texture more 

 strongly marked and distinct. These pieces are all angular, 

 and most of them even quadrangular; and are a foot and 

 upwards in size : they are very thickly heaped together, but 

 still in such a manner that the intervening mass of gneiss may 

 always be distinguished. The streaks of different pieces lying 

 near each other are often parallel ; but they also frequently 

 take different directions, and do not, therefore, follow the 

 direction of the cleavage of the basis. " This wonderful 

 rock is not a conglomerate ; the basis is too distinctly charac- 

 terised as gneiss : but it must be owned that this appearance 

 bears some resemblance to the manner in which the pudding- 

 stone is found in gneiss at Valorsine, and in the lower Valais, 

 according to Saussure. It appears to be an older gneiss which 

 was destroyed during the formation of the newer gneiss."* 



Mr. Weaver has remarked, that the apparently brecciated 

 rocks are connected by insensible gradations with mica-slate, 

 and even with the fundamental granite itself: and is of 

 opinion that neither the mere occurrence of matter mechanic- 

 ally divided in the composition of rocks, nor the curvatures 

 or inflections which their strata sometimes display, entitle 

 them to a place among the transition formations ; for these 

 are characters common to all classes of rocks, f 



Having now examined the structure of the primary rocks, 

 we are the better prepared to enquire into the nature of the 

 relative position of the granitic and schistose rocks. 



* Leopold Von Buch's Travels in Norway and Lapland, Jameson's edition 

 P. 94. f Geol. Trans, vol. v. p. 196. 



