20 Cleology, ^c. of the Connecticuti 



Glandulous Gneiss. 



This is very abundant, especially in the gneiss east of 

 Connecticut river. Indeed, a considerable proportion of 

 that range is occasionally glandulous, presenting numerous 

 dval masses, chiefly of felspar. The layers of this variety 

 of gneiss are usually very distinctj and it contains a large 

 proportion of mica, which is usually of a blackish colour; 

 and thus it is easily distinguished from the porphyritic gran* 

 ite abQve described. 



3. tioRNBLENDE SlATE, ClEAVELAND. 



Coloured V^ermillion, Red, and clouded with India Ink. 



This is an anomalous and perplexing rock. It is not 

 generally well characterised in this region : but I have put 

 it down, because a rock approaching nearer the characters 

 of this than of any other, occurs in considerable abundance 

 along the Connecticut. I have no confidence however that 

 I have given in all cases its exact situation or extent. Yet 

 I believe that wherever this stratum is coloured on the map, 

 the rocks may be found in the vicinity. Thus in the range 

 extending from Belchertown to Guilford, Ct. a person willgen- 

 erally find this rock more or less abundant in crossing from the 

 secondary rocks to the gneiss : but sometimes he may thus 

 Cross and miss of it, unless he make an excursion to the right 

 or left; and sometimes he must cross a portion of the gneiss 

 before he reaches it. The continuity of the strata of this 

 rock seems to be much less perfect than in the gneiss or 

 mica slate, and the direction of the strata if often oblique to 

 that of other rocks : — a remarkable instance of which occurs 

 in the south east corner of Halifax, Vt. The dip of the 

 Strata Varies from 45° to 90°, and the schistose structure in 

 the purest specimens is very perfect, the layers varying in 

 thickness from half an inch to three inches. 



But there is another difficulty in ascertaining the limits of 

 this rock. It is no easy matter to draw the line between it 

 and gneiss, all, or at least, two of the ingredients of the lat- 

 ter rocks beinj; sometimes present, while mor.e than half of 

 the rock is hornblende. Indeed, I have sometimes been dis* 



