'Transactions of the Bombay Geographical Society, from September 1850 to June 1852. Edited by the Secretary. Volume X.' [‎226] (359/458)

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NOTES.
in sulphurets of iron ; and these, in process of decomposition, act on the lim
pervading the clay, and so form sulphates of lime.
By some such process as this, in all likelihood, is the gypsum,—found at Aden
and in the other Arabian volcanoes formed ; it is sometimes fibrous, and always
pure and singularly beautiful. As gypsum is decomposed at a temperaturo
a little above 400 Fahrenheifc> the mineral must have come into existence after the
lavas had become comparatively cool.
In the Great Egyptian desert, betwixt Suez and Cairo—in the deserts of the
Peninsula of Mount Sinai, Dr. Wilson states that on the table-land of Tibbal Tib
about 5,500 feet above the level of the sea, he found marine sand and gravel*
Here he found sulphate of lime, exactly as it occurs near Suez (Lands of the
Bible, vol. 1. p. 264 edit. 1847.)—Dr. Hoffmeister describes a sort of terrace 1500
to 2000 feet high, on the mountains near Suez, covered with gravel and travelled
Stone f on which fragments of selenite and gypsum were to be seen in abundance,
He describes along white vein of Anhydrate as here running across the Rocks,
(Travels in Ceylon and Central India, p. 90 edit. 1848—).
All along towards Palestine, and by the shores of Arabia and the Persian Gulf The historical term used to describe the body of water between the Arabian Peninsula and Iran. ,
and so down to Scinde ; then again upwards to the confluence of the Five Rivers
forming the Indus, veins of selenite, in every direction, traverse the salt shell
gravels and sand which cover the rock, and which as already stated, belong to the
newer Pliocine formation. The shells, indeed, are often as fresh as those to be
found within high-water mark, and when the surface of the ground is covered
with a heavy dew it would require no effort of imagination to suppose that the
sea had just retired, and might return again next tide—the mirage exhibiting the
likeness of expanses of water near at hand, heightening the delusion.—Nothing
can contrast more strikingly with the gravel and rolled pebbles everywhere
prevailing than the fine fibrous or tale-like veins of selenite which make their
appealance in all dilections. They sometimes branch off from a common centre
as if filling up a gioup of cracks j sometimes they are to be seen stretching for
miles almost in a straight line across the country.— {Sometimes they are partly
covered oyer with sand—occasionally the wind blows the drift around them, the
veins arising in lines some inches above the surface. In this case the p'ates
are fiequently seen to have fallen over, and to lie scattered about in pieces over
desert, letaiuing on all occasions the sharp edges and bright polished surfaces
which contrast so strikingly with the material around.—I have never found
em to extend more than a few inches, 10 or 12 at most, under the
ground * and have, on all occasions been able, with a little scraping, to eradicate
vein. Jn the vicinage of the veins salt is always particularly abundant}
consisting, generally, of a mixture of muriate and carbonate of soda. When the
>ot dry Kumsin wind blows, the surface feels crisp and hollow, and yields under
^ie eet like wet ground which has been much tunnelled by moles and is partially
rozen. On oidinary occasions it feels damp and clammy, the finer particle®