Geology, S^c, of the Connecticut. 49 



two miles, he will have repeated opportunities of observing 

 the same fact ; the river having worn away the ro ks so as 

 to afford a fine chance for observation. Let him now re- 

 turn and cross the mouth of Fall river eastward, following 

 up the north bank of the Connecticut, and he will find 

 the same red slate, cropping out about fifteen rods, when he 

 will come to another ridge of greenstone, wwJer which the 

 slate passes. If he follows the junction of the rocks ob- 

 liquely up the hill, on the east side of Fall river, a hundred 

 rods in a northeasterly direction, he will observe the green- 

 stone lying upon the slate more distinctly. Let him return 

 to the bank of the Connecticut, where the sandstone slate 

 passes under the greenstone, and he will observe them both 

 extending in the same manner into the stream. If he now 

 go eastward along the bank of the river, he will find green- 

 stone twenty rods, and then the same or nearly the same 

 slate, rising on the back of the greenstone at an angle of 

 forty-five degrees. Thus will he have conclusive evidence 

 of the alternation of these rocks. This alternation, cross- 

 ing this same spot, is represented in the profile accompa- 

 nying the map. No. 8 is the first ridge of greenstone above 

 mentioned: No. 9 the sandstone slate, rising on its back: 

 No. 10 the second ridge of greenstone; and No. 11 the 

 second stratum of the slate. This second ridge of green- 

 stone, as already marked, extends northeasterly into Gill 

 and terminates in the west part of Northfield. 



Another spot for observing the alternations of greenstone 

 and the coal formation is one hundred rods south-east of 

 Lyman's tavern, on the north-east side of Mount Tom, in 

 Northampton. A small stream here crosses the road, and 

 in its bed and banks several distinct beds of greenstone, 

 some of them not more than one or two inches thick, may 

 be observed at low water. 



In the southern part of that extensive greenstone ridge ex- 

 tending from Amherst to Meriden, the sandstone of the 

 coal formation may often be seen on the west side of the 

 greenstone, lying underneath it. The shaft of the copper 

 mine at Newgate prison passes through the greenstone and 

 enters the sandstone: and Dr. Percival informs us (Jour. 

 Sci. Vol. 5, p. 42.) that in Southington, "sometimes the 

 sandstone can be very distinctly seen cropj ing out below 

 the greenstone on the west side of the ridges." At the 



Vol. VI.— No. 1. 7 



