Prof. Pictet on the Ice-ccroes of the Jura and the Alps. S 
ramids of ice, 15 or 20 feet in height, by 5 or 6 wide. v 4 There 
began (says he) to appear at the top of the entrance, a mist 
which comes out of it all winter, and which announces or ac- 
companies the thaw of the ice.” — 44 The hotter (he continues) 
the summer is, the greater is the quantity of ice.” 
In 1727, at the time of the camp of the Saone, the Duke de 
Levi sent a great number of waggons daily, and carried off all 
the ice both of the pyramids and from the bottom of the grotto, 
which was entirely uncovered. This fact, compared with the 
abundance of ice found there in 1743, by M. De Cossigny, 
proves that the cause of congelation exists, notwithstanding the 
removal of the ice, and that the ice is very quickly formed. 
The following is the appearance which the grotto presented 
to Professor Prevost, in August 1769. 
44 The interior of the grotto,” says he, ; 44 appeared to be di- 
vided into thi*ee compartments, distinguished from each other by 
the shape of the rocks, and by the difference of the phenomena. 
On entering this place, in a very hot day, in the middle of Au- 
gust, I felt a chilling cold ; and the first object which struck my 
eye, was a mass of ice, fed by the water which distilled constant- 
ly, drop by drop, from a sort of source in the roof. The cavern 
is entirely covered, from the entrance, to where the bottom be- 
gins to rise, with a pavement of solid ice, in which are several 
holes, where the water appears cold, and almost at the freezing 
point. In sounding one of these wells, the depth of the ice up- 
on the bottom appeared to be about a foot. According to the 
report of my guide, it appeared that, in winter, the ice formed 
great icicles, or stalactites, which hung from the roof, and melt- 
ed or fell in spring. This circumstance, and some others, change 
the number and disposition of the masses and pyramids which 
rise from the icy pavement of the cavern.” 
44 The evaporation is considerable. It often produces a thick 
fog in the interior of the grotto. M. De Cossigny found this fog 
more visible in August than in October ; but there was none when 
I visited it. v 
To these observations, we shall add the important remark, 
that this grotto is hollowed out naturally in a low hill, and con- 
sequently that its entrance is in the atmospheric region the mean 
temperature of which is far above the freezing point. It mugt 
a 2 
