Geology of Deerfield, fyc. 109 



its suaunit. This ridge does not rise so high as the pudding- 

 stone on the west of it, as may be seen in the view of strata 

 with the map. It commences on the west bank of Connecticut 

 river, about a mile north of the hill C, and increases in eleva- 

 tion nearly to the spot where it disappears at the fall of the 

 river in Gill. This rock does not appear to rest on sandstone, 

 but to descend through it, where there is an opportunity for 

 observation. Deerfield river has worn a passage through the 

 sandstone and greenstone 150 feet deep, and the greenstone 

 passes under its bed, and the sandstone, at a few rods distant 

 lies on each side of the greenstone. A similar fact has been 

 noticed at the fall in Connecticut river, in Gill. Yet I have 

 coloured this greenstone secondary on the map ; for it is cer- 

 tain that Mount Tom rests on sandstone, and it is stated by 

 Professor Silliman, that the same rock does in Connecticut. 

 Could we penetrate deeper below the surface, it is probable 

 the same would be found to be the case with this greenstone. 



As stated above, this rock disappears near the cataract in 

 Gill, and it is succeeded by puddingstone. But four miles 

 farther north, it again emerges in Bernardstone, though it 

 rises but little above the surface. Here its character is 

 changed. The hornblende is more crystalline, and the rock 

 becomes decidedly primitive, as you approach a mountain of 

 argillite and mica slate, into which it passes, and no greenstone 

 has been observed north of this. It terminates not far from 

 the hne of Vermont. The red sandstone and conglomerate 

 also terminate on the opposite side of the river in Northfield. 



The greenstone in the above described range, is of a finer 

 texture than the same rock in Connecticut ; and the feldspar, 

 in some specimens, is scarcely discernible with a microscope. 

 Indeed, in many instances, the eye would decide the rock to 

 be basalt. Much of it is fissile, the laminae varying from half 

 an inch to a foot in thickness. This is most perceptible among 

 the loose masses ; but it exists also in that in place. Whether 

 this circumstance be accidental, I will not attempt to decide. 



A large proportion of the greenstone of our vicinity consti- 

 tutes the base of amygdaloid. The imbedded substances are 

 calcareous spar, quartz, chalcedony, analcime, prehnite, &c 



