PREFACE. 
mountains ; have examined the lakes, and sought out the natural means of com¬ 
munication between different parts of this wide and unsettled territory. At an 
early period, I commenced a series of magnetic observations, particularly on the 
variation of the magnetic needle and magnetic intensity. I found, however, that 
observations of this kind required more time than could be spared from the spe¬ 
cified duties of the survey, and they were mostly abandoned. 
In the reports which I have made, I have, to some extent, embraced all these 
objects ; having endeavored to keep in view the design of the survey, namely, to 
make it as useful and practical as possible to the different parts of the district, 
and to bring to light the resources, such as are available not only at the present 
time, but those which may become so by future enterprise. 
It will be found, on examination of this report, that New-York is well supplied 
with many natural productions important in the business of life, and that in iron 
she is particularly rich, and is still in the possession of means to make her rich 
ores available in consequence of the extent of her forests. Though these posses¬ 
sions are not of a nature to foster our pride, yet inasmuch as they are gifts of 
Providence, they demand our gratitude, as yielding an abundant supply of mate¬ 
rials of the utmost importance to the interests of a growing community, and call¬ 
ing forth the industry, skill and enterprise of our citizens in preparing them for 
use. 
The doctrines which have been advanced in this report, are such as appear 
now to be warranted by the structure of the field in which the observations were 
made, particularly those which relate to the origin of primary limestone and 
metallic veins. Probably the same doctrines will find support in other districts. 
I infer this from the reports of several geologists whose attention has been 
directed to the same subject. 
In introducing a description of the rocks lying mostly in a belt between the 
New-York State line and the Ploosic mountain range, I was actuated by a wish 
to impart a more perfect knowledge of all the lower rocks. In doing this, I am 
sensible that I have added very little to the amount already given the public in 
different Essays by Professors Dewey and Hitchcock, and also by the Messrs. 
Rodgers of Pennsylvania and Virginia. Notwithstanding all that has been done, 
there is still a great want of local observations carefully made, which will throw 
more light upon the relations of the masses to each other, and upon the grada¬ 
tions of mineral character. In proposing a separation of these rocks from other 
systems, I was influenced partly by the opinion, more than once expressed, that 
