Glacières; or, Freezing Caverns

by Edwin Swift Balch

Romain Joly, in 1779, claims to have visited Chaux-les-Passavant on the 19th of September (year not given). His account seems largely borrowed from the one in the Histoire de l’Académie Royale des Sciences, in 1686. He says: “This ice is formed by the drops of water which fall from the roof, and which freeze because of the chill of the cave. In the winter there is no ice, but running water.” He says nothing, however, about the ice forming in summer.

The Citoyen Girod-Chantrans visited Chaux-les-Passavant in August, 1783, and reached the conclusion, from all he saw and heard, that the cave did not freeze in summer nor thaw in winter, and that it was really a natural ice house. He was aided by the notes of a neighboring physician, Dr. Oudot, who had made observations in the cave, and among others, had placed stakes of wood, on the 8th of January, 1779, in the heads of the columns he had found in the cave; and on the 22d of February, 1780, had found these stakes completely covered with ice, forming columns 30 centimeters in diameter.

Hablizl, in 1788, wrote that the ice in the cave near Karassoubazar formed in the spring by the snows which melt, run into the cave, and refreeze. He also thought that there was less ice there in the fall than in the spring, that it diminishes in July and August, and that the idea, current in the neighborhood, of the formation of ice in summer, is a mistake.

Professor Pierre Prévost, in 1789, gave an accurate explanation of the formation of the ice in Chaux-les-Passavant. He says: "Weighing carefully the local circumstances, one discovers in truth a few causes of permanent cold. But these causes seem rather suited to keep up a great freshness or to diminish the heat of summer, than to produce a cold such as that which reigns in the cavern. First of all, big trees throw shade over the entrance; it is, I was told, forbidden under severe penalties to cut down any of them, for fear of depriving the grotto of a necessary shelter. In the second place, this entrance is situated almost due north, leaning a little to the east, which is the coolest exposure one can choose, and the one most suited to help the effect of the icy winds which blow from that quarter. Finally the slope is steep and the grotto deep and covered with a thick vault. These three conditions united constitute, as it seems to me, a very good ice house; by which I mean a reservoir fit to preserve during the summer, the ice which may bank up in winter.

“But how does this ice bank up? One knows that the outside waters above form on the roof, during the winter, long drops and stalactites of ice. These icicles, which hang down and increase constantly by the drip from the same source which formed them, fall at last, carried away by their own weight, and form so many centres, around which freeze the waters with which the floor of the grotto is always inundated. At the same time, the blowing of the north wind accumulates snow at the base of the slope, which is uncovered in part and exposed above to all the vicissitudes of the weather. Thus during the winter is formed an irregular heap of ice and snow, which the first heats of spring begin to make run, but which the heats of summer cannot finish dissolving. The winter following has therefore even more facility to augment the mass of these ice pyramids, which have resisted until the fall. And if men did not work at diminishing it, it might happen that it would fill the entire cavern at last to a great height.

“I am therefore strongly inclined to think that the process of nature is here precisely similar to that of art; that without any especial cause of cold, the natural glacière of Besançon conserves in the moderate temperature of deep caverns, the heaps of snow and ice which the winds and the outside waters accumulate there during the winter; and that the melting of these snows and of these accumulated ices forms little by little the ice floor, scattered over with blocks and pyramids, which one observes there during the summer.”

Horace Bénédict de Saussure, the great Swiss scientist and mountaineer, in 1796, published a number of observations about cold current caves in various parts of the Alps. He found that in summer the air blows outward at the lower end, and that in winter it draws inward. His explanation is that in summer the colder air in the tube is heavier than the outside air and displaces it by gravity; while in winter the rupture takes place in the other direction, since the column within the tube is warmer than the outside air and therefore is pushed upwards by the heavy air flowing in. He concludes that evaporation due to the air passing internally over moist rocks suffices to explain the phenomenon of low temperatures and that such caves have a rather lower temperature in the Alps than in Italy owing to the greater natural cold of the Swiss lake region. An experiment of his is worth mentioning. He passed a current of air through a glass tube, 2.5 centimeters in diameter, filled with moistened stones, and found that the air current which entered with a temperature of 22.5° came out with a temperature of 18.75°, that is with a loss of 3.75° of heat.

Robert Townson, LL.D., in 1797, published an account, perhaps the first in English, of a glacière cave. He says of Szilize: "Ice I truly found here in abundance, and it was mid-summer, but in a state of thaw; the bed of ice, which covered the floor of the cavern was thinly covered with water and everything announced a thaw. I had no need to use my thermometer: however I placed it in the ice and it fell to 0° of Réaumur: I then wiped it and placed it in a niche in the rock, at the furthest part of the cavern, a yard above the ice and here it remained near an hour: when I returned I found it at 0°. * * * Everything therefore, ice, water and atmosphere in the neighborhood had the same temperature, and that was the temperature of melting ice: 0° Réaumur.

“When then is the ice which is found here, and in such quantities that this cavern serves the few opulent nobility in the neighborhood as an ice house, formed? Surely in winter, though not by the first frost, not so soon as ice is formed in the open air. No doubt, from the little communication this cavern has with the atmosphere, it will be but little and slowly affected by the change. Should therefore, Mr. Bel, or any of his friends, have come here to verify the common report at the commencement of a severe frost, when the whole country was covered with ice and snow, they might still have found nothing here but water, or the ice of the preceding winter in a state of thaw, and the cavern relatively warm; and likewise, should they have visited it in a warm spring, which had succeeded to a severe winter, they might have found nothing here but frost and ice; and even the fresh melted snow, percolating through the roof of this cavern, might again have been congealed to ice. I observed frequently in Germany in the severe winter of 1794-5, on a sudden thaw, that the walls of churches and other public buildings, on the outside were white and covered with a hoar frost, and the windows on the same side covered with a rime.”