198 
ADDITIONAL REMARKS ON ICE CAVES. 
within the lower part of a hillock of about the same height as the little mount of 
Illetzkaya. Seeing from their position, that such masses of ice cannot be the residue 
of a winter deposit, Professor Pictet accounts for their formation by extending the 
views of De Saussure, respecting the descending currents of cold air, which in hot 
summers traverse the artificial mound of broken pottery at Monte Testaceo near 
Rome, as well as the sides of certain rifted calcareous hills in Italy and Switzer- 
land. Professor Pictet argues, that in his ice-caves (as in certain mines with ver- 
tical shafts above them and horizontal galleries on the lower sides of the hills) the 
downward current of air during summer must acquire, during its descent, the tem- 
perature of the vertical portion of the crevices through which it passes ; that 
temperature being in general at least as low as the mean temperature of the place. 
He also supposes (with De Saussure) , that the air descending through the fissures 
in the strata, must be still further cooled by the refrigerating effects of evaporation, 
derived from the moistened materials which it encounters in its progress. 
If this explanation be applicable to the ice-caves near Besancon and in the Jura, 
it applies, we conceive, much more strongly to our case in Russia, where the nu- 
merous icicles pendent from the roof of the cavern and the stalagmitic crust of ice 
on the floor, equally indicate a previously wet and damp roof, affording a passage 
to water ; whilst the excessive dryness of the external air of these southern steppes , to 
which we have specially adverted, must contribute most powerfully to the refrige- 
rating effects of evaporation. We may add, that this view is supported by refer- 
ence to the climate of the plains of Orenburg, in which the great wetness of spring 
caused by the melting of the snow, is succeeded by an intense and dry Asiatic 
heat. These conditions, cooperating with the form of the grotto, the fissures above 
it, and the horizontal opening into it at the foot of the hill — features quite analo- 
gous to the vertical shafts and horizontal galleries of mines, referred to by the 
Genevese Professor — seem to us completely to explain the phaenomenon of Illetz- 
kaya, and with it all those examples of ice-caverns mentioned by Pallas in still 
more southern latitudes. 
P.S. We intended, as announced, to terminate this chapter with a review of the 
Organic Remains of the Permian strata, but feeling that this important subject 
could not thus be done justice to, we have devoted an entire chapter to its con- 
sideration, giving at the same time our ultimate view ol the correct equivalents of 
the Permian deposits in Western Europe. 
