Two peasants visited this cave three times in the winter season, viz. on October 22, November 26, and on Christmas Day; and one of them, by name Chavan, drew up an account of their experiences, which was read by M. Colladon before the Societe de Physique et d’Histoire Nat. de Geneve in 1824. The peasants found very little ice in columns at the time of the October visit, and there were signs of commencing thaw. The thaw was much more pronounced in November, when the ice had nearly disappeared even from the lowest parts of the cave, and they found the air within quite warm. On Christmas Day they had great difficulty in reaching the glaciere, and narrowly escaped destruction by an avalanche, which for a time deterred them from prosecuting the adventure: they persisted, however, and were rewarded by finding only water where in summer all was ice, and a temperate warmth in the cave. They observed that the roof had fissures like chimneys.
This account was so circumstantial, that the only thing left was to attempt an explanation of the phenomena reported, and such explanations have not been wanting. But M. Thury was not quite satisfied, and he determined to visit the cave in the winter of 1860-1. Accordingly, accompanied by M. Andre Gindroz, who had already joined him in his unsuccessful attempt to reach the Glaciere of the Pre de S. Livres, he left Geneva on the 10th of January, and slept at the Chartreuse in the Valley of Reposoir. As the party passed through the village of Pralong du Reposoir, the peasants told them with one accord that they would find nothing but warmth and water in the cave; but when M. Thury asked had any of them seen it themselves, they were equally unanimous in saying no, explaining that it was not worth anyone’s while to go in the winter, as there was no ice to be seen then,—a circular line of argument which did not commend itself to the strangers.
At the very entrance of the grotto, they found beautiful stalactites of clear ice; and here they paused, till such time as they should be cool enough to enter, for the thermometer stood at 70 deg. in the sun, and their climb had made them hot. On penetrating to the farther recesses of the cave, where the true glaciere lies, they found an abundance of stalactites, stalagmites, and columns of ice, with flooring and slopes of the same material: not a drop of water anywhere. The stalagmites were very numerous, but none of them more than three feet high; some of the stalactites, fifteen or so in number, were six or seven feet long, and there were many others of a smaller size. M. Thury was particularly struck by the milky appearance of much of the ice, one column in particular resembling porcelain more than any other substance. This is a not unusual character of the most beautiful part of the decorations of the more sheltered ice-caves, as for instance the lowest cave in the Upper Glaciere of the Pre de S. Livres; the white appearance is not due to the presence of air, for the ice is transparent and homogeneous, and the naked eye is unable to detect bubbles or internal fissures.