172 
GEOLOGY OF THE FIRST DISTRICT. 
composed of gravel, pebbles and boulders, with numerous small pond-holes in the depressions 
between them. A boulder of serpentine, containing diallage, was seen on the road-side 
between Commac and the toll-gate on the road towards Dix hills. 
li'erruginous conglomerate, in pebbles and small boulders, and a ferruginous sandstone 
with limonite as a cement, are common in the hills that begin on the west side of the Smith- 
town valley, and extend to Huntington. Fossil wood was found in some of the masses of 
brown iron-stone and ferruginous sandstone.* A single large pebble, or small boulder of 
brown iron-stone, was found with the iron-stone containing the petrified wood, three miles 
northwest of Commac. 
Red granite, white granite, gneiss, slaty hornblende rock, and a kind of sienite composed 
mostly of hornblende, such as is frequently called primitive greenstone, are common as 
boulders and pebbles between Commac and Huntington. The hornblende slate and primitive 
greenstone strongly resemble those in the vicinity of Lantern hill in North-Stonington (Con.), 
and the range of those rocks north. There may be similar ones west of New-Haven, that 
I have not seen. 
On Lloyd’s neck in Huntington, granular white limestone and dolomite, hornblende slate, 
hornblende rock, granite, porphyritic gneiss and common gneiss, were seen among the 
boulders and blocks, both in the drift deposits, and on the shore where they had been washed 
out of their former position. Granite, gneiss and trappean rocks are the most abundant 
among the boulders. 
On West neck in Huntington, the boulders are rather common ; and among them, granite, 
gneiss, porphyritic gneiss, trap, and hornblende slate are the most common^ 
The country between North-Hempstead and Jericho, except within a mile and a half of the 
latter place, is a part of the Hempstead plains, and is like almost all the portions of Long 
island south of the range of hills, sloping almost insensibly to the eye from the hills to the ocean, 
and composed mostly of sand loam and gravel. Near Jericho, the road leads into the swells 
of the hills ; and these are, like those of the chain of hills stretching through the island, com¬ 
posed of loamy gravel, with an abundance of pebbles and boulders. The red iron-stone, 
brown iron ore, and ferruginous conglomerate, were seen more abundantly between Jericho 
and Oysterbay, than in any other part of the island. The boulders and pebbles consist 
mostly of granite, gneiss, quartz rock, mica slate, talcose slate, chlorite slate, with some 
hornblende rock ; and the latter is massive, laminated and fibrous in texture. The mica slate, 
talcose slate, and chlorite slate are rare. A few boulders of serpentine containing anthophyl- 
lite were seen one mile south of Norwich, on the east side of the road, among loose stones 
that had been-collected from the fields to make a stone fence. 
* This was petrified wood, converted to limonite by the hydrated peroxide of iron replacing the ligneous fibre. 1 was not 
deceived in this matter, fori am perfectly familiar with the numerous aspects of fibrous limonite. 
t Prof. Briggs saw a boulder of sparry limestone, and two others of white granular limestone, on the shore, about a mile east 
of Fresh Pond creek. 
