2' Prof. Pictet on the Ice-caves of the Jura and the Alps . 
Two other caverns which likewise contain ice all summer, are 
found in the mountains of Faucigny ; the one upon that called 
Brezon, at some distance to the south of Bonneville ; the other 
in the south-west declivity of Mount Vergy, in the valley of Re- 
posoir, not far from Cluse. I have recently visited the three 
last : Before speaking of them, I shall describe briefly that of 
La Baume, which I have not seen, but of which I have found 
very detailed descriptions ; one in a letter addressed by M. De 
Cossigny to M. De Reaumur, in 1743, and inserted in the first 
volume of the Memoir es des Sgavans Etr angers, (p. 195.), with 
an engraving, containing a plan and section of the grotto ; and 
the other in a letter from Professor Prevost, addressed to the 
editor of the Geneva Journal, and published in the number for 
March SI. 1789- From these two sources, I have principally 
taken the details which follow. 
M. De Cossigny visited this cavern twice, in the month of 
August 1743, and in October 1745. He took the plan of it, 
and made several interesting observations upon the physical phe- 
nomena which its interior presented. The following is an abridg- 
ment of them. 
The cavity is 64 toises in length, by 22 at the widest part; 
the bottom inclines downwards very rapidly from the entrance, 
as there is a descent of 30 toises in its length ; the height of the 
vault, which is of an elliptical form, varies from 10 to 15 toises. 
M. De Cossigny, in his first journey, found that the thermo- 
meter stood a degree of Fahr. above the freezing point, in the in- 
terior; whilst at the entrance without, it was at 77° Fahr. in the 
month of August. In the month of October 1745, the ther- 
mometer was at 32® in the interior, and 50° at the entrance. 
In both visits, he found that the bottom of the cavern presented 
a surface of ice, with a little water in the cavities. 
Towards the extremity, the ice assumed the form of conical 
stalactites, in consequence of the drops of water which fell from 
the roof freezing successively. 
In the Memoirs of the Royal Academy of Sciences for 1712, 
we find the account of a visit to this cavern in September 1711, 
by M. Billefez, of Besan^on. “I found, 11 says he, 44 that the inner 
end of the cavern, which is flat, was covered with ice 3 feet in 
thickness, which was beginning to melt. 11 He also saw three py- 
