22 J. D. Dana— Geological Relations of the 
ting these Lower Silurian beds; and (4), to ascertain, conse- 
quently, how far the kinds o crystalline rocks found in the 
conformable series can be used as a test of geological age. 
8 the fossils of the limestone had been discovered only in 
Vekiaoh, it was required, in order to extend the conclusions to 
the rest of the Green Mountain region, that the Vermont lime- 
stone should be proved to be the same stratigraphically with 
that of the region to the south; and this was done by ascer- 
taining (1) the essential I continuity of the limestone fon the 
north to the south and south-southwest, and (2) its association 
with similar rocks frola mdith to south, under similar strati- 
graphical relations; and finally (8), by the discovery of Lower 
Silurian fossils in the part of these belts of limestone that reach 
into and beyond Dutchess cone and also in the associated 
Taconic schists of that Coun 
By these means, it has back shown that the schists of die 
Taconic range, t the limestone belts on either side, and various 
oe schistose rocks and limestone belts farther east 
and west, are comprised within the Lower Silurian formation, 
and that the whole series was displaced together in the upturn- 
ne oe metamorphism by which the Green Mountains were 
made 
The demonstration in my former papers does not reach into 
the region south of the limits of Dutchess County and of the 
cag is a event . Connecticut. I present now observa- 
e points from this more southern region in the 
State of New York, avin the discussion of the facts from 
hppa As another paper. I have not am ag Saree to work 
In my paper “On the. Hudson River age of the Taconic 
Schists,” published in this Journal in 1879, the accompanying 
map exhibits the fact that the Lower Silurian schists and lime- 
stones of Dutchess County have their southern limit = git or 
among the Archean rocks of the Highland range. igh- 
land Archean area extends eastward from the BPadabe over 
Putnam County, to a distance less than twenty miles, falling 
short of the New Bngland boundary by four or five miles— 
the rocks at Brewster, west of and along the Havleen railroad 
being of the Highland character, even to ‘the existence of a great 
iron-ore bed, while those farther east are mostly distinct i kind 
and system. The extreme breadth of the area is about fifteen 
miles; but the outside rocks, just referred to, send prolonga- 
tions ‘through its supposed boundary, and cover part of its 
interior. 
a7. vars Dale, ae ae xvii, 57, 1879; the writer, ibid., xvii, 375, and 
xviii, 61, 1879; W. B. ne ibid., xvii, 389, and xix, 50, 451, 1886; R. FP. 
Whi itfield, ibid. " xviii, ies “1879 
