Ice-Caves of France and Switzerland

by G. F. Browne

When M. de Cossigny visited the cave, there were thirteen or fourteen columns of ice, from 6 to 8 feet high, and he was in consequence inclined to doubt the accuracy of the statement of M. Billerez, that in his time (1711) there were three columns only, from 15 to 20 feet high. But my own observation of the shape of the columns suggested that the largest of all was probably an amalgamation of several others; so that it is not unreasonable to suppose that after the Duc de Lévi removed the large columns seen by M. Billerez, a number of smaller columns were formed on the old site, and that these had not become large enough to amalgamate in 1743.

Not satisfied with these visits of August and October, M. de Cossigny visited the cave in April 1745. He found the temperature at 5 A.M. to be exactly at the freezing point, and at noon it had risen 1°. From this he concluded that the stories of the greater cold in the cave during the summer, as compared with the winter, were false.

In 1769, M. Prévost, of Geneva, visited the cave, as a young man; and in 1789, he wrote an account of his visit in the Journal de Genève (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 glacière 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. Prévost found only one column, from 6 to 8 feet high.

In 1783 (August 6), M. Girod-Chantrans visited the Glacière of Chaux (so called from a village near the glacière, on the opposite side from the Abbey of Grâce-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°·9 F. two feet above the floor, and at 78° 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 glacière at various seasons of the year, and a précis of these notes forms the most valuable part of his account.

Dr. Oudot, the physician in question, found ten columns in January 1778, the largest of which was 5-1/2 feet high. The flooring of ice was nowhere more than 15 inches thick, and the parts of the rock which were not covered with ice were perfectly dry. The thermometer--M. Girod-Chantrans used Réaumur, so I suppose that he gives Dr. Oudot's observations in degrees of Réaumur, though some of the results of that supposition appear to be anomalous--gave 22° F. within the cave, and 21° F. outside.

In April of the same year, the large column had increased in height to the extent of 13 inches; and the floor of ice on which it stood was 1-1/2 inch thicker, and extended over a larger area than before; the thermometer stood at 36°·5 F. and 52° F. respectively in the same positions as in the former case. In July, the large column had lost 6 inches of its height, and the thermometer gave 38°·75 F. and 74°·75 F.

In October, the large column was only 3 feet high, and many of the others had disappeared, while their pedestal had become much thinner than it had been in the preceding months. There was also a considerable amount of mud in the cave, brought down apparently by the heavy rains of autumn. The thermometer gave 37°·6 F. and 63°·5 F.

On the 8th of January, 1779, there were nine columns of very beautiful ice, and one of these, as before, was larger than the rest, being 5 feet high and 10 feet in circumference. The temperatures were 21° F. and 16°·15 F. in the cave and in the open air respectively.

Tradition related that, before the removal of the ice in 1727, one of the columns reached the roof, (Prévost calculated the limits of the height of the cave at 90 and 60 feet,) and this suggested to Dr. Oudot the idea of placing stakes of wood in the heads of the columns he found in the cave, in the hope that ice would thus collect in greater quantities under the fissures of the roof. Accordingly, he made holes in three of the columns, and established stakes 4, 5, and 10 feet high, returning on the 22nd of February, after an interval of six weeks, to observe the result of his experiment. He found the two shorter stakes completely masked with ice, forming columns a foot in diameter; and the longest stake, though not entirely concealed by the ice which had collected upon it, was crowned with a beautiful capital of perfectly transparent ice. The columns which had no stakes fixed upon them had also increased somewhat in size, but not nearly in the same proportion as those which were the subject of Dr. Oudot's experiment. The thermometer on this day gave 29°·5 F. and 59° F. as the temperatures.

It may be remembered that I found one very beautiful column, far higher than any of those mentioned by Dr. Oudot, and higher than those which M. Billerez saw, formed upon the trunk and branches of a fir-tree. I have now no doubt that the peculiar shape of another--the largest of the three columns which were in the cave at the time of my visit--is due to the fact of its being a collection of several smaller columns, which have in course of time flowed into one as they increased separately in bulk, and that its height has been augmented by a device similar to that adopted by Dr. Oudot. The two magnificent capitals which this column possessed, as well as the numerous smaller capitals which sprang from its sides, will thus be completely accounted for.