Professor Thury tells a story to the point. He visited the Grand Cave de Montarquis in mid-winter. All the peasants told him there would be no use going, as there would be no ice in the cave. He tried to find even one peasant who had been to the cave in winter, but could not. He then visited it himself and found it full of hard ice. On his return he told the peasants of his discovery. They were staggered at first, finally one exclaimed: "It makes no difference; in genuine glacières there is no ice in winter." It will be difficult, probably, to eradicate this belief and the consequent theories among the uneducated people in the vicinity of glacière caves, for their imperfect observations will keep it alive. In refutation, it may be said that the winter's cold theory is the direct opposite of the summer's heat theory, and that all the observations and all the facts which prove the one, disprove the other. Within two or three years, however, the formation of small quantities of ice has been observed during the summer months in one or two caves. This has taken place in mountain caves situated at a high altitude at times when the air outside has dropped below freezing point during the night. There is, therefore, nothing inconsistent in this fact with the winter's cold theory: indeed it is only a widening of it in the meaning of the word winter.[47] [47] See Part III.: Beilsteinhöhle, page 235. Part IV.: Professor Cranmer, page 310. _Chemical Causes._--Non-scientific persons, on first hearing of glacière caves, almost always suggest that to form the ice there must be salts in the rocks. Probably they connect unconsciously in their minds "ice caves" and "ice cream." Chemical causes, however, have never appealed to scientific men.[48] There are only two places I know of where salt is reported. One is the Ice Spring in Oregon, which is said to be slightly saline in taste; the other is the Cave of Illetzkaya-Zatschita, where the gypsum hillock, in which the ice is found, overlies a bed of rock salt. Repeated experiments in letting lumps of glacière ice melt in my mouth have convinced me personally that in all cases the water is exceedingly pure and sweet, a fact mentioned in the very first notice extant about glacières, the letter of Benigne Poissenot in 1586, who speaks of the deliciousness of the water in Chaux-les-Passavant. To sum this matter up briefly, it can be safely asserted that all causes, which would fall under the head of "Chemical causes," must be entirely eliminated as possible cold producers. [48] See Part IV.: Billerez, page 270; Hacquet, page 271.