Professor Pictet read a paper on these glacières before the Société Helvétique des Sciences Naturelles at Berne, in 1822, which is to be found in the Bibl. Universelle de Genève.[[77]] M. Pictet left Geneva in the middle of July to visit the caves, but found himself so much knocked up by the first day's work, that he sent on his grandson to the Glacière of the Brezon, and gave up the attempt himself. The young man found it to be of small dimensions, 30 feet by 25, with a height of 10 or 12 feet. The ice on the floor was believed by the guide to be formed in summer only, and was placed too irregularly to admit of measurement. Calcareous blocks almost choked the entrance, and an orifice in the shape of a funnel admitted the snow freely from above, and was partly filled with snow in July. Cold currents of air proceeded from the rocks in the neighbourhood of the glacière, giving in one instance a temperature of 38°·75, the temperature in the shade being 51°. Within the cave, the temperature was 41°.
M. Morin visited this glacière in August 1828. He describes it as a sheltered hole, in which the snow collects and is preserved.
M. Thury examined it in August 1859, and gives the same account. He, too, found the current of air which the younger Pictet discovered, but in the cave itself the air was perfectly still.
It was clearly, then, no great loss to miss the Glacière of the Brezon; but that on the Mont Vergy, in the Valley of Reposoir, appears to be much more interesting. Professor Pictet found himself sufficiently strong after a day's rest to pass on to Scionzier, and up the Valley of Reposoir, accompanied by the well-known guide Timothée, whose botanical knowledge of the district is said to be perfect. He had conducted MM. Necker and Colladon to the glacière in 1807, and believed that no savant had since seen it. The rocks are all calcareous, with large blocks of erratic granite. The glacière lies about 40 minutes from the Châlet of Montarquis, whence its local name of La grand' Cave de Montarquis. Before reaching it, a spacious grotto presents itself, once the abode of coiners: this grotto is cold, but affords no ice, and near it M. Morin found a narrow fissure, leading into a circular vaulted chamber 15 feet in diameter, in which stood a solitary stalagmite of ice 15 feet high.
The entrance to the glacière itself is elliptical in shape, 43 feet broad at the base, and the cave increases in size as it extends farther into the rock, the floor descending gently till a horizontal esplanade of ice is reached. This esplanade was 66 feet by 30 at the time of Pictet's visit, deeper in the middle than at the sides, and mounting the rock at the farther side of the cave; there was a small stalagmite at one side, but that would seem to have been the only ornamentation displayed. The temperature was 34°·7, a foot above the ice, and 58° in the external air. Timothée had been in the glacière in the previous April, and had found no ice,--nothing but a pool of water of considerable depth. M. Thury, in August 1859, found two sheets of ice in the lowest part of the cave: one, nearly 50 feet long, was partially covered with water; the other, presenting an area of about 14 square yards, showed more water still. There were no stalactites and columns such as M. Morin had found in August 1828, nor even the low stalagmite which Pictet saw in 1822. The summers of 1828 and 1859 were exceptionally hot, and this fact has been held to account for the smaller quantity of ice seen in those years. M. Thury found the cold due to evaporation to be considerably less than 1° F.,[[78]] and he and M. Morin both fixed the general temperature of the cave at 36°·5; they also found a current of air entering by a fissure in the lowest part of the cave, but it did not disturb the whole of the interior, for in one part the air was in perfect equilibrium. M. Gampert,[[79]] in the summer of 1823, found a strong and very cold current of air descending by this fissure, along with water which ran from it over the ice; he believed that this was refrigerated by evaporation, in passing through the thickness of the moist rock.
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 Société de Physique et d'Histoire Nat. de Genève in 1824.[[80]] 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 glacière, 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. André Gindroz, who had already joined him in his unsuccessful attempt to reach the Glacière of the Pré 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° in the sun, and their climb had made them hot. On penetrating to the farther recesses of the cave, where the true glacière 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 Glacière of the Pré 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.
The temperatures at 1.25 P.M. and 2.12 P.M. respectively were as follows:--In the sun, between 3 and 4 feet above the snow, 72°·1 and 70°·5; in the shade, outside the cave, 36°·7 and 35°·8; at the Observatory of Geneva, in the shade, 27°·3 and 28°·2, having risen from 24°·5 since noon. In the cave, 1 foot above the surface of the ice-floor, the thermometer stood at 24°·8; and in a hole in the ice, some few inches below the surface, 24·1. In the large fissure, which has been already mentioned as the source of the summer currents of air, the temperature at various points was from 29°·3 to 27·5. The circumstances of these currents of air were now of course changed. Instead of a steady current passing from the fissure into the cave, and so out by the main entrance into the open air, strong enough to incline the flame of a candle 45°, M. Thury found a gentle current passing from the cave into the fissure, sufficient only to incline the flame 10°, and near the entrance 8°, while in the entrance itself no current was perceptible at 4 P.M.
M. Thury remarks that less current was to be expected in winter than in summer, because the upper ends of the fissures would be probably choked with snow, and their lower ends with ice. It is evident that the current which passes up into the fissure in winter, is favourable to the introduction of the colder air from without; while the opposite current in summer keeps up a supply of cold air in the cave, and so increases its powers of resisting the attempts of the heated external air to make a partial entrance. Both these currents, then, favour the glacial conditions of the cave, and to some extent counterbalance the disadvantages of its situation: viz., its aspect, towards the south-east; the large size of its opening to the air, and the absence of all shelter near the mouth, such as is so often provided by trees or rocks. The small depth of the cave, scarcely amounting to 18 feet below the level of the entrance, is also a great disadvantage.