548 
GEOLOGY OF THE FIRST DISTRICT. 
The Primary rocks in Dutchess county occupy Pawlings, the eastern part of Beekman, 
the southeastern and southern part of Fishkill, the eastern part of Dover, and a small part of 
Pineplains and Stanford. The rocks in the southeastern parts of the county are precisely 
like those described as the Highlands of Putnam county, and are parts of the same moun¬ 
tains. 
Granular quartz rock was observed on the eastern side of the Dover valley in Dover, 
adjacent to the gneiss rocks ; but this and the contiguous white dolomitic limestone belongs to 
the metamorphic rocks, and have been described. 
The mass of Primary rocks in Pineplains and Stanford, is called Mount Stessing. Its 
highest peak is probably elevated nearly a thousand feet above the level of the lake on its 
eastern side. It is composed of gneiss and hornblendic gneiss with some granite, all of which 
are like the rocks of the Highlands. The strata range N. 15° to 20° E., and dip from seventy 
to ninety degrees to the westward. The mountain is entirely isolated, like an island, sur¬ 
rounded entirely by the quaternary and the rocks of the Champlain division). The Potsdam 
sandstone rests on the primary at the southwestern end of the mountain, and this is covered 
by the grey limestones and the slates of the Champlain division. The slates on the western 
side of the mountain are broken and crumpled up in the greatest confusion. 
BlackwelVs island, and the contiguous part of the island of New-York, are gneiss, often 
traversed by veins of granite. The gneiss dips to the eastward at a high angle, and the strike 
is about N. 20° to 30° E. 
The little reefs and islands near Hurlgate are also rocks of the same character, contain¬ 
ing more or less hornblende. 
Barn island. Biker's island. Little Barn island, the Brothers, and some others have a 
nucleus of the same rocks, mostly covered by the drift and quaternary depositions. 
The small islands near Newt-Rochelle and in that vicinity, have a basis of rocks of gneiss, 
both fissile and thick-bedded, and sometimes hornblendic like those at Hurlgate. The strata 
are nearly vertical, and the strike is about north-northeast and south-southwest. 
On the post road from New-York to Albany, limestone is quarried for a flagging stone, 
near Livingston’s village in Westchester county. Chlorite and nacrite are the substances that 
make it fissile. 
Northeast from Singsing, the limestone becomes micaceous, and so modified as not to be 
easily recognized. Much of it is very fissile, and so much intermixed with mica and felspar, 
that it might with propriety be called a calcareous mica slate ; but much of it contains so little 
carbonate of lime as to be distinguished with difficulty. About three miles northeast from 
Singsing, the gneissoid mica slate is succeeded by gneiss and hornblendic gneiss. 
Limestone was seen in place in two localities, on the road from Pines bridge to Peekskill. 
The limestone on the hill southeast of Peekskill is much bent and contorted, and is variegated. 
When broken, it presents bent lines of grey, black and white, like an agate. 
After crossing the limestone and talcose slate of Peekskill creek, the traveller comes 
suddenly upon the granitic and gneissoid rocks of the Highlands, and he observes augite 
to abound in many places in these rocks, and in some it enters as a constituent. The 
