76 T. S. Hunt on Laurentian Rocks in Massachusetts. 
these various regions accompany the crystalline limestones. 1, 
at that time, accepted without examination the view maintaine 
by Mather and H. D. Rogers, that these limestones in southern 
New York and New Jersey were altered Silurian strata, al- 
though mineralogically identical with those farther north of 
undoubted Laurentian age. Led by this conclusion to attach 
comparatively little importance to mineralogical and lithologi- 
cal resemblances, and guided by other considerations given 
the paper just referred to, I then suggested that the crystalline 
limestones and their accompanying rocks in northeastern Massa- 
chusetts might probably be of Devonian age. The subsequent 
investigations of Hall, Logan and Cooke in the Highlands of 
New York and New Jersey have however left no doubt that 
Newburyport, in company with Dr. ‘ ns of 
that place, had, for the first time, an opportunity of che “4 
the gneiss imestones in question. Their aspect confirmed 
zoon, and I may here remark that I had already, so long ago 
as 1864, caused slices to be made of a specimen of limestone 
from that locality, which were then examined by Dr. Dawson 
with negative results. In November, however, Mr. Bicknell 
visited a quarry about 
visited Newburyport and got 
