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 walls, so that little doubt could remain of this being a gen- 

 uine dike. 



No. 9. Sandstone, 52 feet. 



No. 10. Greenstone, 5 feet. 



No. 11. Sandstone, 45 feot. 



No. 12. Greenstone, 10 feet. 



No. 13. Sandstone, 19 feet. 



No. 14. 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. 



Thus we have eight dikes in a distance of 21 rods. Some 

 of them require a little attention to discover them ; but 

 most of them are very distinct. Some of them we traced 

 several rods on both sides of the road, in a direction per- 

 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 lean a 

 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 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 least,) occur 

 in the old red sandstone on the right hand side of the turn- 

 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, cuttit.g through a precipice twenty or 

 thirty feet high, and maintaining an uniform width of about 

 a foot. This crosses the strata nearly at right angles; but 

 makes an angle with the horizon of about 45° dipping to the 

 aouth west. On 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. 



Vol. VI.— No. L 8 



