58 Geology, Vc. of the Connecticut. 
same distance. The dike along with the sandstone appears 
to pass under a hill of greenstone. 
n the same turnpike, a few rods north-easterly of North- 
ford ee re tone, four or five dikes occur; but they are 
so hidden by the soil as not to be particularly instructive. 
Tn pean glo Durham to New-Haven on the same road, the 
first low ridge of greenstone, which we cross, exhibits some- 
thing, which I was almost disposed to denominate a dike of 
coarse pudding stone, of the coal formation, in greenstone. 
Certainly, there appears a peculiar juxtaposition of the two 
rocks; but probably they exist in beds. 
Two or three miles north of the dikes of which a profile 
is given, Dr. Percival found several others; and perhaps 
they are a continuation of the same. He found one also on 
ce road from Farmington to Hartford in the rocks of the coal 
orma 
tion. 
The greenstone found in these dikes has usually the dark 
compact aspect of basalt—resembling, however, much of 
the greenstone found along the Connecticut. Yet it seems to 
wantthe hI 
collected from the most perfect dike above deperted ‘half a 
mile east of East Rock, even approach to wacke. This rock 
gives an argillaceous odour, is of a greenish grey color, has 
an uneven fracture, is dull; and much softer than ee aa 
greenstone; so that it may be cut with a knife: —and on 
parison with a specimen of pure wacke from Calton Hill, (Ea- 
inburgh,) which was analyzed by Dr. Webster, it does not ap- 
pear to differ, except in its greater hardness and perhaps less 
— to the touch. I have little doubt that these dikes will 
ong be denominated basaltic dikes: but, for the reason 
Formesty alleged, I forbear to name them thus. They are 
an interesting feature i in our geology, and deserve more at- 
tention ; and it is peculiarly fortunate that they should be 
situated so pear a geological school and the first mineral cab- 
inet in our country, 
Juxtaposition of Secondary Greenstone and Primitive Rocks. 
The actual contact of these has never been observed 
along the Connecticut; and I know of but three places 
where there is a probability of finding the junction—viz. in 
the northeast part of Belchertown, in East-Haven and Bran- 
