ROCKS OLDER THAN THE TACONIC SYSTEM. 53 



general term, and often covers botli ranges. But keeping up the tlistinction denoted l)y 

 the subordinate portions of the most easterly range, as lloosic and Mansfield mountains, 

 and tile Taconic range upon tJie west, we shall find tiiat the geological characler of the 

 two are quite dissimilar, anil well worthy of observation on that account. The former 

 are tiie great primary or schist ranges, the subordinate members of which are gneiss, mica 

 and talcose slate, and hornblemle, among which arc many beds and veins of granite, 

 limestone, serpentine and trap. There is no clear line of distinction between the schistose 

 rocks : mica slate is the predominant rock, in connection with which we find gnei.ss and 

 talcose slate and hornblende, and with the two last are the serpentine and steatite beds, 

 which in some instances are beds of passage ; for instance, the great beds of steatite in 

 Middlefield and Chester pass into talcose slate and serpentine. 



The principal object in speaking of the schists, is to liring into mind their position and 

 character. Situated to tlie east, running in parallel ridges with the Taconic range, and 

 being composed in their entire length of schistose masses, we are furnished tlureliy with 

 the probable reason why the lower masses of the Taconic system arc so perfectly schistose 

 also : the latter are derived from the former; the abraded materials of the one make up and 

 constitute the consolidated masses of the other ; they are the first products from the primary 

 rocks; the sea in which these materials were deposited was the most ancient, with little 

 carbonaceous matter, and probably with a temperature rather above the present seas ; the 

 masses are less changed in color and aspect ; and being crystalline, also, the lower slates 

 of the Taconic system appear like those of the older schists of the Primaiy system : they 

 are regenerated rocks, possessing the characters belonging to the parent lieds from which 

 they are derived. The fact is notorious that the talcose slates of Berkshire are like the 

 talcose slates of the Hoosic or Green mountains ; and yet a close inspection of the two 

 ranges of schistose rocks will satisfy most geologists that they are not of the same age, or 

 of the same system. 



That it is possible for a sedimentary rock to retain or assume the characters of the parent 

 rock, is rendered highly probable l)y the characters of the rocks or slates connected with the 

 Rhode-Island coal beds. Here, in connection with the conglomerate probably of llie Old 

 Red sandstone, there is much material which is a talcose slate, differing but slightly from the 

 talcose slate of the Taconic system ; or, in other words, it is like that of Berkshire county. 

 I conceive that the slate of the Old Red, and which I Ixdieve Prof. Hitchcock calls wacke 

 slate in his Massachusetts Report, is one derived directly from the magnesian slate of the 

 Taconic system lying in proximity thereto : the quartz pebbles are evidently of that kind 

 of quartz in the same rocks. The beds of conglomerate, with which these slate beds are 

 in connection, do not appear to be metamorphic : the whole seems to be merely indurated 

 or hardened slate, the original particles being talc and mica, with some fine quartz. The 

 rock, when complete, is merely an ordinary talcose slate. 



I do not, however, deem it essential to prove the origin of the rocks which happen to 

 lie in the ranges belonging to the Taconic system. It is of little consequence what the 



