304 



Scientific Geology. 



yellowish. What the disseminated minerals are, I have not ascer- 

 tained. From the general aspect of this rock where it has been 

 weathered, one would not suspect it to be limestone; and it scarcely 

 exhibits any traces of stratification. (No. 454.) On the east, at the 

 village of South Lee, this rock is succeeded by white dolomite, whose 

 strata dip w r est about 45°. A mile farther to the east, they are per- 

 pendicular. 



A little east of the village in Stockbridge, I found specimens which 

 contained quartz and mica, and which appeared to be limestone pass- 

 ing into mica slate, just as in Canaan, Ct. (No. 458.) The same 

 rock I found in the east part of Lanesborough. (No. 457.) 



In passing from West Stockbridge to Chatham, N. Y. we find the 

 gray limestone traversed by innumerable veins of white quartz, so 

 that the mass becomes a real breccia. (No. 453.) This rock is quite 

 abundant near the line of the State. As we pass westerly from this 

 line, the limestone becomes of a darker color and rather more com- 

 pact, and alternates with bastard mica slate and argillaceous slate. 

 Frequently this limestone is traversed by numerous veins of white 

 calcareous spar, giving it a striking appearance. (No. 453.) It is 

 probably interstratified with graywacke slate in Renssalaer and Co- 

 lumbia counties, N. Y. 



I have already mentioned the crystallized tremolites and white au- 

 gite found in the dolomite of Canaan. The same minerals occur in 

 the same variety of rock at Muddy Brook in Great Barrington, and 

 in New Marlborough, and the former in the south part of Lee and in 

 Sheffield. In the 14th vol. of the American Journal of Science, I 

 have described four modifications of the secondary forms of the au- 

 gite ; and Prof. Dewey, in the 8th vol. of the same Journal, mentions 

 a fifth. In Great Barrington, the tremolite is found in beautiful 

 bladed crystals. This mineral is often delicately fibrous, and some- 

 times radiated. Indeed, all the varieties are found at these localities. 

 In Sheffield the fibres are sometimes more than two feet long, and em- 

 brace crystals of iron pyrites. These fibrous masses are mistaken 

 for petrified wood ; to which, indeed, they bear a striking resem- 

 blance. 



Carbonate of lime is often found crystallized in this rock in ta- 

 bular, lenticular, &c. crystals. It is also more frequently found la- 

 minated. The agaric mineral, it is said, is found in a cave in West 

 Stockbridge. Concreted carbonate of lime occurs in the different 



