F.
_The Gypsum Cave of Illetzkaya-Zastchita, in the Steppes of the Kirghis, South of Orenburg_.
The district in which this cavern occurs is a small green oasis on the undulating steppe, lying on a vast bed of rock-salt, which extends over an area of two versts in length, and a mile in breadth, with a thickness of more than 100 feet.

When the thin cover of red sand and marl is removed, the white salt is exposed, and is found to be so free from all stain, or admixture of other material, excepting sometimes minute filaments of gypsum, that it is pounded at once for use, without any cleansing or recrystallising process.
In the immediate neighbourhood of Illetzkaya-Zastchita there are two or three gypseous hillocks, and a cavern in one of these is used by the inhabitants as a cellar, having been artificially enlarged for that purpose.

Sir Roderick Murchison and his colleagues visited this cavern on a hot day in August, with the thermometer at 90 deg.

in the shade, in the course of their travels under the patronage of the late Emperor of Russia.[113] They found the hillock to be an irregular cone 150 feet in height; the entrance was by a frail door, on a level with the village street, and fully exposed to the rays of the sun; and yet, when the door was opened, so piercing a current of cold air poured forth, that they were glad to beat a retreat for a while; and on eventually exploring farther, they found the quass and provisions, stored in the cave, half-frozen within three or four paces of the door.

The chasm soon opened out into a natural vault from 12 to 15 feet high, 10 or 12 paces long, and 7 or 8 in width, which seemed to have numerous small ramifications into the impending mound of gypsum and marl.