so Geology^ ^c. of the Connecticut, 



outlet of Salstonstall's pond in East-Haven, I have observed 

 a grey micaceous sandstone of the coal formation, passing 

 under the greenstone with a considerable dip; and also two 

 miles south of Durham village, on the side of the turnpike 

 leading to New-Haven. 



Dr. Percival, who has examined most of the greenstone 

 ranges in Connecticut on foot, illustrates his views of the 

 relative position of this rock and the coal formation as fol- 

 lows — referring particularly to the vicinity of Berlin. As 

 you ascend the mountain ridges from the west, the lowest 

 rock you find, after leaving the alluvion, is the old red 

 sandstone, represented below by A. Above this lie the 

 argillaceous sandstones of the coal formation, represented 

 by B. The cap of the ridge C is greenstone; precipitous 

 on the west side, but gently sloping on the east. Passing 

 on we come to another stratum of the coal formation ; as 

 D. Next, perhaps, succeeds another ridge of greenstone, 

 E — similar to C; and on its back, we find again the coal 

 formation, F; And sometimes the cap of greenstone is in- 

 sulated, as G. 



Sometimes we find the greenstone resting immediately 

 upon the old red sandstone, without the intervention of a 

 third rock ; as at East and West Rock near New-Haven. 



From all that 1 have seen and learned concerning these 

 rocks, I feel therefore, warranted in concluding, that, as a 

 general fact, our greenstone alternates with, or forms beds 

 in, the peculiar rocks of the coal formation ; and it seems 

 very probable that both these repose upon the old red 

 sandstone. As the slates of the coal formation dip below 

 the eastern horizon, it would seem we are furnished with 

 the reason why the mural faces of the greenstone are almost 

 universally on the western side of the ranges. 



When greenstone rests on the coal formation, the lower 

 part of the greenstone seems to consist of little else than a 

 greyish black, indurated, ferruginous clay. Perhaps even 



