388 J. D. Dana—Hudson River Age of the Taconic Schists. 
certainly a large part of Western Connecticut, and over Hastern 
New York at least to the Hudson. 
That hard gneisses and mica schists are among the included 
formations does not, in any way, affect the evidence or the con- 
clusions here deduced. 
These conclusions coincide partly with those reached by 
Professor Mather, as stated on pages 438, 464, and 628 of his 
Report, namely: (1) That the limestone of Hastern New 
York and the Green Mountain region, including that of West- 
chester County down to New York Island, is of the Trenton 
or Calciferous (Canadian) periods; (2) that the slates, gneiss, 
mica schist and other rocks, directly associated with the lime- 
stone in Massachusetts and elsewhere, are of the Hudson River 
age; (8) that the quartzyte is of the age of the Potsdam; (4) 
that the making of the Green Mountains and the metamorphism 
of Western New England, took place at the close of the Lower 
Silurian. Proposition (1) appears to me to be established, if 
we admit, in addition, that the limestone may in some places 
be in part Primordial, and leave out of consideration, for the 
present, that of Westchester County. Proposition (2) is pretty 
well demonstrated as far as the slates or schists of the Taconic 
il are concerned ; but,—as I present in the second of my 
a : 
region. 
Professor Mather has a separate chapter on “ Primary rocks” 
under which head he includes the rocks of the Highlands, and, 
with these, the gneisses and mica schists of Westchester County 
and New York Island. The distribution of the limestone areas 
of Westchester County with reference to one another and those 
of Connecticut, and their stratigraphical relations to the gneisses 
and mica schists associated with them, are a basis of evidenceon 
this question of age, and the facts I have observed and mapped 
I shall present in a following number of this Journal. 
The nature and stratification of the schistose rocks interven- 
ing between the Connecticut limestone belts I have studied — 
with some detail, and I propose, after further investigations, — 
and the removal of some doubts as to the limits of the included — 
Archean, to make these also the subject of another paper. 
