98 ROCKS AT CAMDEN. 



An inspection of this section, which comprises an extent of about three quarters of a 

 mile, furnislies an epitome of the facts disclosed by the rocks upon this range. The first 

 mass a is the magnesian slate, much wrinkled, and containing masses as well as seams of 

 quartz : it is the nortli portion of the uplift, where the descent becomes rapid towards the 

 river. 



i, is the Stockbridge limestone, clouded, lumpy as it appears upon a weathered surface, 

 intermixed with quartz, siliceous veins, talcose matter, etc. Its beds, when worked, offer 

 veins of calc spar, and imperfect veins of magnesian matter, which appears to result from 

 the decomposition of felspar. The soft matter contains dodecahedral crystals of carbonate 

 of lime, with rough surfaces, which appear to have been formed in the soft matter after its 

 decomposition. The same material is found in numerous places in the limestone at 

 Williamstown, Massachusetts. I have called it magnesian, though probably it is merely 

 a porcelanous clay. 



A trap dyke traverses the hard slate, succeeded very soon by a granitic vein, f and g 

 are portions of fine and coarse slate ; in the latter, imperfect crystals or macles of brown 

 staurotide appear. Some of the faces may be made out ; they possess only the general 

 form of a crystal, but are disclosed by weathering. Nothing at all determinate appears 

 by fracture. 



h. At this point in the section, a mass of quartz comes in, of a bluish color ; grain and 

 texture that of the conmion granular quartz. It is sixty or seventy feet thick ; and froin 

 its presence and relations, I have been led to entertain the opinion that two distinct masses 

 of quartz belong to the system. This fact is borne out by the rocks of Berkshire, Massa- 

 chusetts. Two masses, for instance, appear which are not in the same range, though it 

 is not clear that one is superimposed upon the other as at Goose river, Maine. 



m. Magnesian slate. 



K. Fine brown granular quariz, portions of which are conglomerated : it is the principal 

 mass of quartz, possessing all the characters of the same kind of rock in Massachusetts, 

 Vermont and New-York. It is interlaminated with a dark fine siliceous slate, occurring 

 in mass, though ixiucli corUorted. Portions resemble the talcose slates, in which, as in 

 Rhode-Island, a greenish granular mineral appears, more like epidote than any thing else. 

 Bands of yellow slate also appear, resembling those of Massachusetts which furnish the 

 ocluy iron. 



At /, after rising up from the gorge of the river, and passing over. the succeeding ridge 

 some forty or fifty rods, a fracture appears, which brings (he magnesian slate nearly in 

 contact with tlie quartz over which it lies. It contains at tiiis point also imperfect macles. 

 That the quartz is beneath this mass of slate, is proved by another fracture nearly at right 

 angles to this one, and but a short distance to the westward, where both masses are brought 

 up, the quartz being beneath, and bearing the slate with its peculiar imperfect minerals. 

 The dip and trend in this case is changed to the west and north. 



The thickness of the limestone at this exposure is about two hundred and fifty feet. 

 The portions of the beds adjacent to the others are more or less slaty and impure. The 



