Veins of Greenstone. 



425 



side of Holyoke, have their northwestern edges raised : although, as 

 the mountain makes a gradual curve to the right, the strata appear to 

 be conformed to its sides. Upon the whole, however, while we must 

 admit, it seems to me, that this extensive rsnge was originally protru- 

 ded through the strata of sandstone in the same manner as dykes 

 are, yet it may be better to regard it as a protruding ridge, rather 

 than apply a term to it which has not usually been so extended in its 

 meaning. 



Genuine and distinct veins of greenstone in the new red sandstone 

 of the Connecticut valley, are not common. In Massachusetts I have 

 not met with one : but in Connecticut, they are more common. The 

 following is a sketch of a case of this kind, which I took several 

 years ago, in a ledge a little east of East Rock, near New Haven, on 

 the turnpike road from thence to Middletown. Most of the ledge is a 

 red rather coarse sandstone, from 20 to 30 feet high. The lowest stra- 

 tum is a fine grained red sandstone; the next above it, a coarse gray 

 sandstone, about six inches thick. The rock dips from the observer 

 about 25°; so that it must be represented as horizontal on the section. 

 The vein of greenstone is about a foot wide at the bottom, and some- 

 thing more as it ascends. It appears to consist of indurated clay. 

 It ascends through the sandstone at an angle of about 45° with the 

 horizon, and on the upper side of it the different layers of sandstone 

 are elevated, so as not to correspond with the same layers on the op- 

 posite side of the vein. This upward flexure extends several inches 

 from the vein. The coarse gray stratum above mentioned, exhibits 

 this effect most obviously. 



Greenstone Dyke in New Red Sandstone : East Haven Ct. 



The inferences of a theoretical nature from such a case as the 

 above, if there is no mistake in my representation of it, are too obvi- 

 ous to escape the notice of any one. If we have not proof here of 

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