Geology, §c. of the Connecticut. 57 
having small peices of the greenstone attached to them, and 
exhibiting somewhat of an altered appearance, like the oth- 
er nate so that little doubt could remain of this being a gen- 
wine 
No, O. "Sandstone, 52 feet. 
No. 12. Greenstone, 10 feet. 
No. 13. Sandstone, 19 feet. 
No. - Greenstone, 7 feet. 
No. 15. Sandstone, 7 feet 
No. 16. Greenstone, 4 feet. Here the greenstone is hid 
by the soil as is also the sandstone at the other end of the 
profile: so that by removing this, probably other dikes 
might be discovered. 
hus we have eight dikes in a distance of 21 rods. Some 
of them wed “ litde | asic 2 discover them; but 
most of them ry distinct. e of them we traced 
several eee on B bet sides of = roads in a direction: 
pendicular to the profile. Their width is sometimes sud- 
denly decreased, or increased, several inches, so as to form 
shoulders. They are not exactly perpendicular, but leana 
few degrees to the west; and thus they are made to form 
an angle considerably obtuse on their eastern side with the 
sandstone. The latter rock is often somewhat glazed, hav- 
ingja specular aspect at the place of junction with the green- 
stone, and the two rocks are not unfrequently mutually i im- 
pregnated, for several inches, with each other’s properties. 
I did not notice that the dikes at this place dislocate the 
strata of sandstone: but I paid little attention to this point. 
Several dikes, similar to the above, (three at Jeast,) occur 
in the old red sandstone on the right hand side of the tarn- 
pike from New-Haven to Middletown, on the east margin of 
the salt marsh lying east of East Rock. One of these is 
remarkably distinct, cutting through a precipice twenty or 
thirty feet high, and maintaining an uniform width of about 
afoot. This crosses the strata nearly at right angles; but 
makes an angle with the horizon of about 45° dipping to the 
south west. Qn its roof, or upper side, near the lower ex- 
tremity, a part of the sandstone strata are thrown upwards 
two or three feet; and they are affected laterally about the 
Vor. VI.—No. 1. 8 
