Topography of Quartz Rock. 321 



berland and its vicinity. Its geology is certainly very intricate, and 

 deserves the long and careful study of some one who resides in the 

 vicinity ; and then it should be exhibited on a map of a larger scale 

 than mine. Since it is not in Massachusetts, I did not feel justified in 

 devoting so much time as was desireable to its examination. 



The range of mica slate extending from Webster to the mouth 

 of the Merrimack, often passes into genuine quartz rock, and gener- 

 ally contains a large proportion of quartz. In the south part of this 

 range, in Webster especially, I noticed so much quartz rock that I 

 have represented a patch of it on the map. 



The gneiss formation on the east of this mica slate, especially near 

 the southeast part of Worcester county, is associated with extensive 

 strata of quartz rock. In Sutton and the vicinity, it occupies a con- 

 siderable part of the surface ; and there I have delineated this rock 

 on the map. I have noticed it in several of the towns northeast from 

 Sutton, interstratified with gneiss and hornblende slate. In the east- 

 ern part of Franklin county, in New Salem and Warwick, I have 

 met with it in strata of a few feet wide, interstratified with gneiss. 



Along the western border of the great gneiss range of Worcester 

 county, is another narrow stratum of quartz rock, in some places 

 associated with the gneiss, sometimes with hornblende slate, and 

 sometimes with mica slate. I have represented it on the map as ex- 

 tending only from Leverett to the north line of the State, because south 

 of this place it is very narrow and frequently interrupted. Mica 

 slate is commonly associated with this rock north of Leverett. On 

 the opposite side of Connecticut river, in Northfield, Mass, and Ver- 

 non, Vt. quartz rock forms one of the members of a series of mica 

 slate passing into gneiss, hornblende slate, and argillaceous slate. 

 In Vernon it is liable to disintegration and has been employed for the 

 manufacture of glass. In Bernardston, where it approaches the clay 

 slate, as already remarked, it occasionally takes portions of that rock 

 into its composition. But generally in Leverett and Northfield, it is 

 that variety which contains mica. 



Berkshire county, however, contains the principal repository of 

 quartz rock. Here it is usually associated with mica slate; and al- 

 though it is represented as lying contiguous to gneiss, yet I have 

 given my reasons elsewhere for the opinion that its position is uncon- 

 formable to that of the gneiss. It sometimes forms hills of consider- 

 able elevation : as Monument Mountain in Stockbridge, which is more 

 than a thousand feet high. Compared with the mica slate and gneiss 

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