xxi. 113.
P. 271.
Daubuisson estimated the depth in question at from 46 to 61 feet, while Kupffer put it at 77 feet.
De Saussure found a variation of 2°·25 F. at a depth of 29·5 feet; but this was in a well, where the influence of the atmosphere was allowed to have effect. Naturally, the fissures which there may be in the rock surrounding a cave will increase the annual variation of temperature, by affording means of easier penetration to the heat and cold.
The continued extrication of latent heat by ice, as it is cooled a few degrees below 32° F., appears to indicate a molecular change subsequent to the first freezing.—Phil. Trans., as quoted in the next note.