84 BROWN SANDSTONE, 



Another variety is worthy of net ice ; it is a species of porphj ritic Bandstone at the inferior 

 part of the rock. The felspar is in small angular forms, and verj liable to decompose; 

 and having disappeared in tins way, the quartz is Lefl in a porous rough stale resembling 

 the Pans burr stones, ["he dip and strike of the beds usually conform to the other rocks 

 in the system, being from -0 to 46° E.. and some beds are vertical. This rock is rarely 

 thin-bedded, and bo strongly marked are the transverse natural joints thai the iwdding 

 planes are often nearly obliterated; the planes are, however, often distinguishable by 

 lamina' of siliceous date. 



The Granular quartz is the l< asl regular in its continuation of any of the rocks of the 

 Taconic n stem : it generally appears in insulated mountain masses, surrounded apparently 

 by other rocks : still, taking the range of our system as a guide, we find it prolonged far 

 to the north and smith, though not continuously. 



Some facts bave Led me to indulge for the present the opinion that two distinct masses 



-i in the Taconic system: one adjacent to the western base of the Hoosic range; the 

 Other, still farther west. The former is the most persistent and important, and rises into 

 mountains from twelve to fifteen hundred feet high. Such is Oak hill, between Adams 

 and Williamstown, Massachusetts; also in the easl part of Bennington, Vermont; and 

 Monument mountain, in the south part of Berkshire. 



Mica is extremely rare in granular quartz: its surfaces are often sprinkled with talc. 

 It is sometimes interlaiiiinaied with a dark siliceous slate, hut these lamina; rarely exceed 

 half an inch in thickness. It passes, however, into a rock of this character, and forms a 

 tolerable (lagging stone. 



This rock, from its extreme hardness, resists the comminuting agents which destroy 

 other rocks ; and hence, in the vicinity of its heds, the cohhleslones are usually very 

 abundant, and till the soil to a great depth. These soils, therefore, are often worthless, 

 from the impossibility of removing the stones. Where only a moderate quantity of this 

 kind of stone is present, the land is of excellent quality, and well adapted to corn and rye, 

 particularly the latter. 



Some difference of opinion exists in regard to the system to which the granular quartz 

 belongs. Prof. Hitchcock places the rock in the Gneiss, or Primary schists. He remarks, 

 Bpeaking of the topography of the rock, "I have represented all the quartz rock in the 

 Slate as associated with mica slate, talcose slate or gneiss. It is more or less connected 

 with other rocks, a- with limestone in Berkshire, and with argillaceous slate in Bemardston. 

 But m all other cases, except in regard to gneiss and mica slate, ii is little more than a 

 juxtaposition of the two rocks ; whereas the quartz rock alternates with, and passes imper- 

 • ■ ptthly into, gneiss and mica slate ; and, in fact, it might he regarded very properly as a 

 memher of the gneiss and mica slate formations."* 



I am unable, from the perusal of the above extract, to satisfy myself that the different 

 beds spoken of are not in reality of different ages. Whether this suggestion is true or not, 



* Massachusetts Report, pp. 589 - 590. 



