GEOLOGY OF THE FIRST DISTRICT. 
CHAPTER IX. 
PRIMARY ROCKS. 
Under this term of Primary rocks, are included those usually called by that name, that have 
not yet been described as metamorphic, though some of them are probably of the same age 
as the Metamorphic rocks. This is particularly the case with the intrusive or plutonic rocks, 
as granite, sienite, hornblende rock, some of the trappean rocks, and the metalliferous beds 
and veins intertruded among these rocks, and that have been altered by metamorphic agency. 
The hornblendic gneiss, micaceous gneiss and mica slate may also perhaps be referred to the 
same periods, as having undergone marked changes in their mineralogical characters. 
The Primary region embraces the counties of New-York, Westchester and Putnam, the 
southeast part of Dutchess, the west and northwest parts of Rockland, the southeast part of 
Orange, with a few islands of these rocks surrounded by others in Orange and Dutchess, and 
a very small part of Richmond county in the southern part of the First geological district; 
and the northern and northwestern parts of Saratoga and Washington counties in the northern, 
part of that district. 
The rocks in the Primary region are composed of the same kinds of rock, which are not 
very numerous t and each of these kinds is very similar in mineralogical characters, in mine¬ 
ral contents, and in geological associations. 
The rocks of the Highland mountains, and of the mountains of Saratoga and Washington 
counties, are very similar, and different from those of the lower hills in Queens, New-York, 
and Westchester counties. 
Although I have spent twelve years of my life in the midst of the Highlands, and although 
m the habit of spending most of my leisure during a part of that time in unravelling its com¬ 
plicated geological phenomena, I feel that I have but begun to develop those facts that are of 
high importance, not only in scientific, but in economical geology. The general geology is 
very simple, but when we come to examine particular strata, veins and beds of useful mine¬ 
rals, and trace out the connection of the different localities, it is found to require much time 
and an intimate practical knowledge of the subject. The strata, in many places, are trans¬ 
verse to the general direction of the strike of the rocks, in consequence of transverse upheaves, 
of which there are several striking examples. Again, faults are numerous, and in many of 
these the heaves are not only vertical but lateral, and sometimes to a distance of one thousand 
