Everything I have personally observed in freezing windholes shows that in them also the cold of winter and not evaporation is the cause of the ice. They answer to the same tests as other glacières, of geographical distribution and altitude, nearness of ice to the outside, thermometric observations, and dampness of the air when the ice melts. Equally with other glacières, the movements of air in windholes do not depend on the presence of ice, but the ice does depend on the movements of air and a water supply at the proper time. A proof that it is the cold of winter which makes the ice in windholes, is that the ice is always found at the lower extremity, for the reason that it is at that end that the cold air enters and to that end that the water gravitates. The reason that ice is more rarely found in windholes than in apparently static caves, is due to the movements of air. Unlike the caves where the heavy cold air preserves the ice by remaining pent up, as soon as the outside temperature rises the heavy cold air in windholes tumbles out at the lower opening and is replaced gradually by air at a higher temperature. This also flows out and when it is above freezing point, it naturally melts the ice and becomes humid: in fact, it vaporizes the ice as it passes, and dissipates the moisture into the outer air. It is, however, certain, that in caves with a temperature some degrees above freezing point, when there is either running water or strong drips, evaporation may be, and sometimes undoubtedly is, a factor in lowering the temperature somewhat.[64] As in some windholes there is occasionally moisture on the rock surfaces where the air current passes, the evaporation from these surfaces doubtless lowers the temperature of the draughts, and it may be, also those of the rock surfaces, a little. [64] See Part IV.: De Saussure, page 274. See also _Les Abimes_, 1894, page 564. Further observations, however, will be necessary in regard to evaporation underground, as the data are still insufficient to make absolutely positive statements.[65] I fail to see any evidence to show that evaporation ever lowers the temperature of draughts underground below freezing point, only that it may help to lower them to something less than they would otherwise be. Taking all the facts which I have myself observed, and all I have read of in the reports of others, my own conclusion is that we have no proof that evaporation underground is ever strong enough to produce ice. [65] Several observers consider evaporation as more or less of a factor in the production of cold underground. It is suggested also, that in certain cases, at high altitudes, evaporation tends to prevent the melting of the ice in windholes, but this is not proved, as yet. See Part IV.: De Saussure, page 274; Fugger, page 296; Trouillet, page 298; Martel, page 300; Lohmann, page 302.