210 



Scientific Geology. 



The following distinct varieties of rock compose the new red sand- 

 stone in the valley of the Connecticut. 



1. Conglomerates. A conglomerate, composed almost entirely of 

 the ruins of granite and mica slate, forms, in connection with a sand- 

 stone of similar character, all the lower beds of this formation; and 

 these two varieties embrace all the rock that has usually been denom- 

 inated old red sandstone. The two varieties pass into each other by 

 insensible gradations, and even the finest portion of the sandstone is 

 coarse. The strata are from one to two, and even three or four feet 

 thick ; and for the most part, the slaty structure is almost entirely 

 wanting. The prevailing and almost uniform color of the rock is 

 red ; and even the imbedded nodules, when not very large or com- 

 pact, are penetrated with this color. Yet where this rock approaches 

 granite and mica slate, as in Bernardston, Greenfield, Deerfield, 

 Whately, and Southampton, it is somewhat variegated ; some por- 

 tions of it being of a light gray color ; as if a heat so powerful had 

 been applied to it, as partially to expel the iron, or change it from an 

 oxide into some other compound. The nodules of the conglomerate 

 are sometimes one or two feet in diameter ; but for the most part, 

 they are only a few inches thick. A variety occurs in Bernardston, 

 Southampton, &c. ( Nos. 135, 136,) which can hardly be distin- 

 guished in hand specimens from granite ; being composed of frag- 

 ments, but little rounded, of quartz and feldspar ; the latter of a flesh 

 color. Sometimes the nodules, as at Sugar Loaf in Deerfield, are 

 graphic granite, which is often quite beautiful ; the feldspar being of 

 a lively flesh color. 



In Greenfield and Bernardston, near the junction of the new red 

 sandstone formation with the argillo-micaceous slate, the conglomer- 

 ate occurs, composed entirely of argillo-micaceous slate and white 

 quartz. This was obviously derived from the detritus of the slate 

 against which it rests. The general color of this rock is red ; and 

 even the mica slate on which it reposes, exhibits the same color sev- 

 eral feet from the junction. (Nos. 137 to 139.) 



Another variety of conglomerate, which is found only in connec- 

 tion with the upper beds of the new red sandstone, is of a dark, red- 

 dish gray color, and is composed of fragments of mica slate, talcose 

 slate, chlorite slate, hornblende slate, and slaty quartz rock, with oc- 

 casional nodules of quartz, feldspar, and granite. The cement ap- 

 pears to be the same materials comminuted. This is the coarest con- 

 glomerate in the the Connecticut valley. It constitutes a considera- 

 ble part of mount Toby in Sunderland, where the imbedded nodules 



