4 Prof. Pictet on the Ice-caves of the Jura and the Alps. 
also be observed, that, from the form of this cavity, the winter 
snow cannot enter, and therefore cannot, in any visible manner, 
contribute to the formation of the ice in the interior, especially if 
we consider that it is more particularly at the remotest extremity 
of the grotto that the ice is formed and accumulated. 
To conclude this local description, it may be mentioned, that 
the outer surface above the grotto, continues to rise from the en- 
trance, to the distance of 20 toises, and afterwards continues 
nearly horizontal, and covered with wood. By measuring the 
section of the cavern given lengthwise by M. De Cossigny, the 
thickness of the earth above the vault, at the part of the grotto 
which is lowest, that is, at its extremity, will be found to be 
about 150 feet. 
I now proceed to the second cavern of the Jura, which I 
have already mentioned, that of St George’s. To reach the vil- 
lage of that name, we must take the road from Rolle as far as 
Gimel, which is the high road of the valley of the Lake de 
Joux, and which I here quitted for the road to St George’s, 
where I arrived at 8 o’clock in the morning of the 7th of July, 
having left Rolle at 6 o’clock. The barometer gave 281.4 toises 
for the height of St George’s above the lake of Geneva. 
The village is situated precisely at the foot of the last ascent 
of the first line of the Jura; and it is in this slope that the ice- 
cave is situated. We quitted the car in which we had come, 
and began to climb on foot, conducted by the best possible 
guide, as we had the peasant who had hired the ice-cave from 
the commune of St George’s, to whom it belongs. His lease 
has lasted for twenty-five years, on very moderate terms. He 
informed us, as we went along, of the following particulars. 
In ordinary years, it only furnishes ice to a small number of 
families, who pass the summer at Rolle, and in a circle of about 
two leagues round the grotto ; but, in such years as the last, 
when the winter did not furnish a sufficient quantity of ice, to fill 
the artificial ice-houses, Geneva, although eight or nine leagues 
distant, had recourse to this substitute. This circumstance oc- 
curred this year for the third time. It took place, also, in 1818 
and in 1820. 
He carries to Geneva every second day during the summer, 
about twenty-five quintals of ice, which he sells to the hospital, 
