Correspondence. 353 
" Upon the eastern border of New York, adjacent to Vermont, Massa- 
chusetts and Connecticut, is the prolongation of the Appalachian chain of 
mountains. This portion of the chain is known as the Taghkanic range; 
it rises to an elevation of from 1,200 to 2,000 feet, and presents a tolerably 
regular outline throughout its whole extent. Its geological relations are 
interesting, particularly so, as many of the phenomena in connection with 
these rocks bear upon the doctrine of Metamorphisra, and probably there 
is no better field for proving or disproving the doctrine, than the one under 
considerntion. 
^^ The rocks of course are situated between the gneiss of II oosick mountain on 
the east and the Slates of the transition on the west. They occupy, therefore 
geographically as well as geologically an intermediate position; the rocks on 
the one hand bearing a very close resemblance to the Primary on the east, 
and on the other a great similarity to the transition slates on the west. Stilly 
as a whole,the rocks of the Taghkanic range may generally be distinguished 
from those on either side, their general character being derived from the 
presence of a large proportion of magnesia which imparts to the rocks a 
softer feel and a peculiar greenish color. It is not proposed in this plan to 
separate these rocks from the Primary, but to consider the?n as belonging to 
t?ie upper portion, and to speak of them as the Taghkanic rockSy or perhaps as 
the Taghkanic System. There may be many objections to this proposition; 
this is not, however, tlie place to consider them,but we may inquire whether 
it may not, upon the whole, be expedient to consider them under a 
distinct head ; and is it not true, that so long as they are merged in the 
great mass of the primary, or as a portion of the gneiss system, less will be 
known of them, and less interest be entertained for them. Considering 
them for the present as belonging to the Upper portion of the Prinutry, 
the Taghkanic rocks will be composed first of a peculiar talcose slate or a 
magnesian slate in part; in other parts it is Plumbaginous, which strongly 
soils the fingers. Its associated minerals, are milk-white quartz. * * * 
ISecond, of white, gray and clouded limestone, varying in texture from fine 
to coarse granular, often interlaminated with slate, the latter often merely 
coloring the limestone so as to impart that clouded appearance. Serpen- 
tine is never connected with this variety of limestone. Third, of granular 
giia7'<3, or a sandstone generally siliceous and of a brown color * * * 
(Cambrian of Walcott.) 
"There are two or three facts connected with the subject which require 
to be stated in this plan, inasmuch as they bear on the question of the 
propriety of separating the Taghkanic rocks, from the gneiss system. 
The granular quartz, and one of the varieties of the slate, and also the 
limestone, contain minerals in a few instances, belonging to primary rocks; 
thus feldspar occurs in the first, needle-form schorl in the second and 
brown tourmaline in the third. Again, there are masses of the granular 
quartz, which appear like conglomerates, and the whole Taghkanic System 
is clearly stratified and is wholly unconnected with gneiss, serpentine granite, 
sienite, steatite or hornblende. Mica slate with garnets, however, does 
occur in masses among the rocks uf the Taghkanic System, and tliis may 
be considered as a strong argument against the separation of the rocks, as 
