Varieties of New Red Sandstone. 



211 



are sometimes three or four feet in diameter. It extends through 

 Montague, and at the mouth of Miller's river, as well as on the op- 

 posite side of the Connecticut at that place, it may be examined to 

 good advantage. South of Sunderland I have not found it, except at 

 Durham in Connecticut. Unless viewed on a large scale, this rock 

 scarcely exhibits any stratification. The strata are sometimes eight 

 or ten feet thick. (Nos. 140 to 143.) 



At Turner's Falls a much finer and more compact gray conglom- 

 erate exhibits itself, composed of the same materials as the last, ex- 

 cept that it abounds more in quartz and feldspar. (No. 150.) 



A reddish conglomerate, made up of nearly the same materials as 

 that first described, (except that it contains more slate,) abounds 

 among the lowest of the upper beds of this formation. (Nos. 144 to 

 147.) It is not as coarse as the last and the strata are usually less 

 than a foot thick. It is common in mount Toby and on the east side 

 of mount Holyoke in Granby. 



Trap conglomerate is another variety of no small interest. It re- 

 poses on the greenstone on the east side of mount Tom and Holyoke : 

 and consists of a mixture of angular and rounded masses of trap 

 and sandstone, with a cement of the same materials. The nodules 

 are sometimes one or two feet in diameter, and the stratification is not 

 very distinct. I do not doubt but the same rock may be found on the 

 east side of nearly all the greenstone ranges in the Connecticut val- 

 ley. Its thickness is but small, and its mode of production obscure. 

 (Nos. 151, 152, and 285.) 



2 Sandstones. The lowest and most abundant sandstone in this 

 formation has been described with sufficient minuteness, in connection 

 with the conglomerate with which it occurs. It is used somewhat 

 extensively for architectural purposes. (Nos. 154 161.) 



A sandstone, which, at a little distance resembles that just described, 

 is found among the upper beds of this formation in Longmeadow and 

 Wilbraham ; where it is extensively quarried. It differs, however, 

 essentially from the last variety ; being composed chiefly of fine si- 

 liceous sand, with occasional specks of mica, cemented probably by 

 the red oxide of iron : for its 6olor is almost blood red. Its particles, 

 however, do not cohere strongly ; and this forms the only objection to 

 its use in architecture. The extensive quarries in Chatham, Ct. are 

 opened in this rock ; or in a variety closely allied to it. Its strata are 

 thick and rarely exhibit a slaty structure. (Nos. 165, 166.) 



Gray sandstone is not uncommon in this formation ; but it is found 

 chiefly in the upper part of the series ; or rather in the vicinity of 



