108 
GEOLOGY OF THE FIRST DISTRICT. 
districts. These facts, which are well known, led me to think more favorably of the theory 
of M. Longchamps as applied to our nitrogen springs. 
The following facts may also aid in explaining the evolution of nitrogen, and of carbonic 
acid, from some of the nitrogen gaseous springs : 1. As far as my observation has gone, the 
nitrogen springs of eastern New-York are at or near the junction of limestone with a talcose 
slaty rock, that is in some instances perhaps a metamorphic rock. 2. Professor Hitchcock* 
has observed in Massachusetts, and I have observed the same fact in many places in the 
eastern counties of New-York, that the rocks at the junction of the limestone and talcose 
slate are loaded with carbon, and frequently also with pyrites.t Should atmospheric air come 
in contact with these substances by natural means, as by caves or by fissures in the rock, 
which are not filled with water, a high temperature, or the decomposition of pyrites, might cause 
the oxidation of the carbon, of the pyrites, or of both, and a consequent evolution of nitrogen 
and perhaps of carbonic acid. 
Springs, Wells, <^c. 
The springs of Long island are numerous, and present some phenomena worthy of consi¬ 
deration. Around the heads of the bays and reenterings of the coast along the north shore of 
Long island, copious springs break out very little above tide-water level. In some instances 
they boil up through the sand and gravel, so as to form a brook at once ; in others, several 
springs break out at the foot of the bank, and uniting their waters, form a stream. The 
numerous mills and manufactories on the shores of many of the reenterings of the northern 
coast of Long island, and which have no apparent streams communicating with their ponds to 
renew the supply of water, attract the attention of most observers. The water of these 
springs is very pure, in consequence of its having been filtered through beds of nearly pure 
siliceous sand and gravel. It is thrown out at the level of tide water, or at a higher level, 
where there are strata impermeable to it. Some of the most remarkable of these springs 
which are applied to manufacturing purposes, are about Hempstead harbor, at the head of 
Little-neck bay, at the head of Coldspring harbor, and the southwest part of Oysterbay harbor. 
In most parts of Long island, water is not found in quantity, and is not permanent except 
at about the level of the ocean, in consequence of the porous nature of the strata. 
In some places there are local deposits of clay and loam interstratifie'd, which are basin¬ 
shaped, and contain the water. These are more abundant in the hilly regions than in the 
plains. Springs are as abundant and copious on the south side of the island as on the north, 
but they break out at some distance from the shore, in consequence of the land declining almost 
insensibly from the hills. The great plain of Long island extends from the base of the hills 
south to the ocean, descending but a few feet to a mile. On Hempstead plains the wells are 
dug from sixty to one hundred and twenty feet deep, through beds of gravel and sand, before 
* Professor Hitchcock’s Geology of Massachusetts, 1841, pp. 581, 583, 584. 
t Mather’s Geological Report of New-York for 1838, pp. 88, 96, 130. 
