'Transactions of the Bombay Geographical Society, from September 1850 to June 1852. Edited by the Secretary. Volume X.' [‎227] (360/458)

SELENITE OR GYPSUM.
227
the sand adhering to the feet.* Sea salt generally contains from 3 to 4 per cent
of sulphate of soda, magnesia, and lime ; and it seems to me more than probable
that the two former of these acting on the carbonate of lime, the coraline
limestone and shells, which here everywhere constitute the chief elements of
gravel, produce selenite and sodalite. The sulphate of limef originally
existing is probably added to that being brought into existence. The Idea
of Berthollet, that the Trona in the lakes of Ferrar has been produced by
the action of muriate of soda and carbonate of lime, in their pasty state on each
other, has now been generally accepted. Dr. Malcomson’s reports, too, explain
the deposition of soda in the Loonar lake, and a short extension of the theory
seems to me alone capable of explaining the formation of selenite such as that
described. Gypsum, indeed, is usually associated with the great salt formations,
and probably everywhere claims a similar origin ; it occasionally presents
itself in the desert, not as a selenite but as the cementing matter of a strange
species of conglomerate, now in process of formation. This consists of gravel of
the desert with fragments of the earlier remains of the numulite formation, of
bones of camels, horses and birds of prey, and fragments of soda water bottles all
the materials, in short, that are strewn around united together in one promiscuous
mass —At Bombay we have it acting conjointly with carbonate of lime, as the
cementing matter of a great bed of concrete in process of formation under our
raised sea beaches, and about 10 feet beneath the surface, and close on the
medium level of the sea,—All over the vast plain which constitutes the
Deccan or great table-lands of India—patches of sea salt, associated with
carbonate of soda, occur. Many of the wells at Ahmudnuggar are brackish
(says Col. Sykes, p. 425, Geol. Trans.) and a rivulet near by, running into
the Beema, has it source two miles to the N. N. W. which is called the Salt
Brook. The stones in its channel are crusted over with crystals of salt and
carbonate of lime. The river Doon near Bejapore is perfectly salt at
all times. Salt is found between Kirjut and Pairgoon, between Seeroor and
Kouta, and at Kabar Loonee, 12 miles from Poonah,—In all these cases
carbonate as well as muriate of soda is described as found—the former is
eagerly sought after by the washerman. Dr. Gibson mentions that with
these gypsum is always associated, and I have no doubt that every where the
three will be found together.
Captain Dagerfield mentions the occurrence of gypsum in Malwa as associated
with sea salt ; he does not state in what form it occurs* and as I am not aware
of the existence of the saliiirous formation in Central India, I presume it to be
under the circumstances similar to those in which it appears in the Deccan.
* In April 1840, when a hot Kamsin wind was blowing, I found the former state of matters to
prevail; in December 1845, with a fresh breeze from the sea, the latter.
t Rock Salt seldom contains more than 1 and one-tenth per cent of sulphate; sea salt
contains from three to four per cent. May not this be adduced as a cofirmatioaofmy theory j
The Sulphate of the Rock Salt has become decomposed and disappeared.