50 Geology, 4c. of the Connecticut. 
outlet of Salstonstall’s pond in East-Haven, Ihave 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. ove this lie the 
y B. The cap of the ridge C is greenstone; precipitous 
on the west side, but gently sloping on the east. Passin 
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 ba ck, we find again the co 
formation, F; And sometimes the cap of greenstone is in- 
sulated, as 
Sometimes we find the greenstone resting immediately 
upon the old red sandstone, without the intervention oF 
third rock ; as at East and West Rock near New-Have 
From all that I have seen and learned concerning hase 
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 Seisietsss3 are almost 
universally on the western side of the r 
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 
