In 1769, M. Prevost, of Geneva, visited the cave, as a young man; and in 1789, he wrote an account of his visit in the Journal de Geneve (March), which was afterwards inserted as an additional chapter in his book on Heat.[186] He believed that one or two hundred toises was the utmost that could be allowed for the height of the hill in which the glaciere lies,—­a sufficiently vague approximation.  He rejected the idea of salt as the cause of ice, and came to the conclusion that the cave was in fact nothing more than a good natural ice-house, being protected by dense trees, and a thick roof of rock, while its opening towards the north sheltered it from all warm winds.  He accounted for the original presence of ice as follows:—­In the winter, stalactites form at the edges of various fissures in the roof, and snow is drifted on to the floor of the cave by the north winds down the entrance-slope.  When the warmer weather comes, the stalactites fall by their own weight, and, lying in the drifted and congealed snow, form nuclei round which the snow is still further congealed, and the water which results from the partial thaw of portions of the snow is also converted into ice.  Thus, a larger collection of ice forms in winter than the heat of summer can destroy; and if none of it were removed, it might, in the course of years, almost fill the cave.  At the time of his visit (August), M. Prevost found only one column, from 6 to 8 feet high.

In 1783 (August 6), M. Girod-Chantrans visited the Glaciere of Chaux (so called from a village near the glaciere, on the opposite side from the Abbey of Grace-Dieu), and his account of the visit appeared in the Journal des Mines[187] of Prairial, an iv., by which time the writer had become the Citizen Girod-Chantrans.  He found a mass of stalactites of ice hanging from the roof, as if seeking to join themselves with corresponding stalagmites on the floor of the cave; the latter, five in number, being not more than 3 or 4 feet high, and standing on a thick sheet of ice.  There was a sensible interval between this basement of ice and the rock and stones on which it reposed:  it was, moreover, full of holes containing water, and the lower parts of the cave were unapproachable by reason of the large quantity of water which lay there.  The thermometer stood at 35 deg..9 F. two feet above the floor, and at 78 deg.  F. in the shade outside.  M. Girod-Chantrans determined, from all he saw and heard, that the summer freezing and winter thaw were fables, and he believed that the cave was only an instance of Nature’s providing the same sort of receptacle for ice as men provide in artificial ice-houses.  He was fortunate enough to obtain by chance the notes of a neighbouring physician, who had made careful observations and experiments in the glaciere at various seasons of the year, and a precis of these notes forms the most valuable part of his account.