ALLUVIAL DIVISION. 
85 
In Delaware county, alum and sulphate of iron effloresce at an old mine hole in Colchester, 
on Downe’s brook, where copper has been supposed to exist; also at an old mine hole on Dry 
brook in Middletown, two miles from Arkville. 
In Rensselaer county, about one and a half or two miles north of New-Lebanon springs in 
Stephentown, is a locality that has long been known. Sulphate of alumina and iron occur 
there, efflorescing upon the rock, which contains pyrites. Prof. Eaton has described the rock 
as alum slate* Another locality is three miles north of Lebanon springs, eighty rods east of 
the road to Williams College, under a shelving ledge of argillite.f 
In Hoosick township, near the Vermont line, a few miles east-northeast of Hoosick falls, 
is a similar locality, also in the metamorphic slates, and described by Prof. Eaton.| It is 
near the banks of the Wallomsack river, a tributary of the Hoosick, and within a mile of the 
Bennington battle ground. The locality is not of economical importance. 
Alum has been found on the Helderberg;§ at several places in Saratoga county,|| and at 
several on the banks of Fish creek in that county ;1[ on the Shawangunk mountains, in slate 
rock,** and sometimes in the fissures of the grit rock of those mountains.ft 
Sulphate of alumina has been observed on the Helderberg mountain,J| and in Saratoga 
county. §§ 
3. Nitrates of Lime and Potassa. 
Nitrate of lime occurs in small quantity, it is said,|||l under the shelving limestone rocks on 
the left bank of the Rondout, a few rods below the High falls in Marbletown, Ulster county. 
It is known by its deflagrating on hot coals, like nitre. It also has been observed in small 
quantities in the old arches of Fort Putnam, near West-Point, in Orange county.‘HTT In both 
localities, carbonate of lime, sheltered from moisture except that of the air, is exposed to 
animal exhalations, which are the circumstances favorable to its formation. It is formed 
almost every where under such circumstances, and particularly under buildings. Advantage 
was taken of this fact in 1812 and ’13, to make nitre for the manufacture of gunpowder, when 
our supply of this article from foreign countries was mostly cut off. Most of the shelving 
rocks that shelter an area which is kept dry, and especially those under which animals take 
shelter, and the caves where the earth is kept dry, or slightly moist, will afford one or both 
these salts. Large quantities of nitre have been made in such situations, in some parts of our 
country, and may be again, in case of a diminished supply from other sources. 
• Eaton’s Geological Survey of Rensselaer County, p. 20. 
+ Silliman’s Journal, Vol. 15, p. 244. 
X Eaton’s Geological Survey of Rensselaer County. 
Silliman’s Journal, Vol. 5. p. 269. 
II Robinson’s Catalogue of Minerals, p. 148. 
IT Ibid. p. 158. 
** Pierce in Ibid. p. 150 ; Cleaveland’s Mineralogy, p.228. 
tt Bradbury in Ibid. p. 150. 
tt Robinson’s Catalogue of Minerals, p. 132; Survey of Al¬ 
bany County, by A. Eaton; Webster’s Catalogue of 
Minerals, p. 6. 
Steel, Survey of Saratoga county, 
nil Geological Report, Assembly Document, N. V., No. 50, 
1840, p. 245. 
ITIT Prof. J. B. Nott, in Webster’s Catalogue of New-York 
Minerals, 1824, p. 21. 
