Geology, ifc. of the Connecticut, 37 



it seems "the terms primitive and transition are daily be- 

 coming of less importance." 



Quarries have been opened in the Woodbridge argillite 

 and it is employed in New-Haven for building. In Ver- 

 mont also, they have been wrought in Guilford, and Vernon, 

 two also in Dummerston, S. E. of the centre of the town, two 

 in Putney, one and a half miles north of the meeting-house, 

 and one in Rockingham, a mile north of Bellows Falls. In 

 most of these the slate is of a good quality and easily ob- 

 tained ; but at present they are not much wrought on ac- 

 count of the little demand for it, and consequent low price. 



10. Limestone. 



Granular Limestone, Eaton, Index, ^c. 



Colored with India Ink. 



This rock, in the country covered by the map, always 

 exists in beds in mica slate and argillite : never occu- 

 pying, however, so much as half the surface. I have co- 

 lored it in that region where it occurs most abundantly, 

 that is, in the mica slate nearest the argillite and the sand- 

 stone ; although its beds exist in nearly all the mica slate 

 north of Northampton on the west side of the river. It is 

 remarkably uniform in its appearance. Its exterior, when it 

 has long been exposed to the weather, is of a dark brown 

 color, showing more marks of decomposition than any 

 other rock in this region. The carbonate of lime is usual- 

 ly worn away at least an inch deep on the surface, and 

 the silex and mica are left in coarse grains, or warts, or in 

 projecting ridges. When newly broken the mica is uniform- 

 ly of a light gray, and the texture is coarsely granular and 

 dull, except the glimmering of scales of mica. The con- 

 stituents of the rock are carbonate of lime, mica and silex, 

 in somewhat variable proportions. In a specimen sent to 

 Prof. Dewey, he found about fifty per cent of carbonate of 

 lime and fifty of silex and mica. He judged that the silex 

 constituted about thirty five per cent and the mica fifteen : 

 and he judiciously adds, " the mica is in so great proportion,, 

 you cannot call it sihcious limestone. At least, ought it 

 not to be called a granitic aggregate, or silicious limestone 

 mixed with mica ?'* 



