852 J. D. Dana—Helderberg rocks in the Connecticut Valley. 
tral valley of New England at Middletown, it there passing 
out of the area of the Triassico-Jurassic Red Sandstone (which 
continues through to New Haven) by cutting through the me- 
tamorphic rocks of Eastern Connecticut. 
Percival, in his Report on the Geology of Connecticut, states 
that, adjoining the Red Sandstone region on the east, there ex- 
tends, southward from Massachusetts, a range of hornblendic 
and chloritic rocks associated with gneiss, and in some places 
with imperfect quartzite. He remarks that he has traced this 
chloritic and’ hornblendic range into Massachusetts as far as 
Wilbraham, one of the localities of hornblendic rock mentioned 
by Hitchcock, showing that it is identical with the eastern of 
the ranges in Massachusetts. He followed it in Connecticut 
through Somers, Ellington and Glast-nbury to North Chatham, 
in the latitude of Middletown, where it disappears beneath the 
Red Sandstone formation. 
The chloritic rocks include a chloritic gneiss, related to proto- 
gine, and also a compact rock which he says resembles green- 
stone. Percival suggests that this chlorite formation is continued 
on the west of the Red Sandstone formation abreast of New 
nec- 
that 
* Bruce’s Mineralogical Journal, vol. i, p. 145. 
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