rock; the cold of winter, in the same manner, arriving at midsummer.  To this the explorers objected, that the mound contained many caves, but’ only in this particular fissure was any ice found.  Dr. Robinson, astronomer at Armagh, endeavoured to explain the matter by referring to De Saussure’s explanation of the phenomena of cold caves in Italy and elsewhere; but this, too, was considered unsatisfactory.  At length, Professor Wheatstone referred them to the memoir by Professor Pictet, in the Bibliotheque Universelle of Geneva, where that savant improves upon De Saussure’s theory, and applies it in its new form to the case of caves containing permanent ice, in tracts whose mean cold is above the freezing point.  This they seem to have accepted, adding that the climatological circumstances of Orenburg—­a wet spring, caused by the melting of the abundant snows, followed by a summer of intense and dry Asiatic heat—­must be particularly favourable for the working out of the theory, and must also act powerfully in producing the refrigerating effects of evaporation.[114]

The traveller Pallas visited Illetzkaya in July 1769, and describes this gypseous hillock.[115] In his time the entrance by the side of the hill was unknown, as also was the existence of ice in the cavern.  He saw at the top of the Kraoul-nai-Gora, or Watch-mountain, as it was called, a fissure which had once formed a large cavern, into which the Kirghis were in the habit of throwing furs and other materials as religious offerings.  Although the cave had since fallen in, they still kept up a part of the ceremony, marching solemnly round the base of the hill once a year, and bathing in the neighbouring water.  In earlier times, a man had descended through the fissure by means of cords, and found the cold within insupportable, having very probably reached the present ice-cave.

Pallas describes many caves in various parts of Russia, but never seems to hint at the existence of ice in them, though he specially mentions their extreme cold.  Some of these occurred in gypsum, and some in limestone; and the gypseous caves showed universally a very low temperature, though still far above the freezing-point.[116] Thus in the dark cavern of Barnoukova,[117] on the Piana, in a rock of gypsum, while the thermometer in the shade stood at 75 deg..2, the temperatures at various points in the cave were,—­at the entrance 59 deg..36, 25 feet from the entrance 46 deg..4, and in the coldest part 42 deg..8.  This cold he describes as insupportable.  The temperature of the water which had accumulated in the coldest parts of the cave was 48 deg..8, considerably higher than the surrounding atmosphere; from which Pallas concluded that the cold of gypsum-caves is due to the acid vapours which are generally observed in grottoes of this description.  In May 1770, he found snow on the sloping entrance to the cavern of Loekle, in the neighbourhood of the Oufa; but the air of the interior was not colder than was to be expected in a deep cave.