188 
FREEZING CAVERN AT ILLETZKAYA-ZASTCHITA. 
If any thing similar obtains at Orenburg 1 see no difficulty in explaining your 
pheenomenon. Rejecting diurnal fluctuations and confining ourselves to a single 
summer wave of heat propagated downwards alternately with a single winter wave 
of cold, every point at the interior of an insulated hill rising above the level plain 
will be invaded by these waves in succession (converging towards the centre in the 
lorm of shells similar to the external surface), at times which will deviate further 
from mid-winter and mid-summer the deeper the point is in the interior, so that at 
certain depths in the interior, the cold-wave will arrive at mid-summer and the heat- 
wave in mid-winter. A cave (if not very wide-mouthed and very airy) penetrating 
to such a point, will have its temperature determined by that of the solid rock 
which forms its walls, and will of course be so alternately heated and cooled. As 
the south side of the hill is sunned and the north not, the summer-wave will be 
more intense on that side and the winter less so ; and thus though the form of the 
wave will still generally correspond with that of the hill, its intensity will vary at 
different points of each wave-surface. The analogy of waves is not strictly that of 
the progress of heat in solids, hut nearly enough so for my present purpose. 
“ The mean temperature for the three winter months, December, January, Fe- 
bruary, and the three summer months, June, July, August, for the years 1836, 7, 8, 
and the mean of the year, are for Ekaterinenburg as follows : — 
1836. 
Winter. 
- 10°-93 R. 
Summer. 
+ 1 1°*90 R. 
Annual Mean. 
+ 1° 22 R. 
1837. 
- 12 o- 90 
+ 12°-93 
+ 0°-30 
1838. 
- 12°-37 
+ 12°-37 
+ 0°-60 
Mean. 
- 12°-07 R. 
+• 12°-40 R. 
+ 0°-70 R. 
+ 4°-83 Fahr. 
+ 5 9°'9 Fahr. 
+ 33°-57 Fahr. 
“ The means of the intermediate months are almost exactly that of the whole 
year, and the temperature during the three winter as well as the three summer 
months most remarkably uniform. 
“ This is precisely that distribution of temperature over time which ought under 
such circumstances to give rise to well-defined and intense waves of heat and 
cold ; and I have little doubt therefore that this is the true explanation of your 
phsenomenon. 
