* * * Naturally this opening [the entrance] was small, but to give easier entrance, it was enlarged to its present size. * * * If the entrance had been left a small opening, as it naturally was, it is my belief that the temperature of the interior of the cave would be lower in summer than it is, and the ice would not disappear as soon as it does." Mr. Robert Butler, of San José, Cal., investigated the question of cold air draughts coming from the glacière cave and from the freezing shaft he examined in Montana. He wrote to me, in 1898, that he found that one notices or imagines to notice a draught of air, especially on hot days. Rapidly walking into the cave from the hot air without to the rapidly cooling air within produces the same nervous sensations as though one were to remain stationary and the air were to pass by from the warm to the colder portions. A distance of twelve meters finds a difference in temperature of fifteen degrees Centigrade. Twelve meters can be walked quickly, so quickly that the nerves cannot become accustomed gradually to the change of temperature. The rapidly cooling air does actually produce the sensation of cool air passing by one's face. It produces somewhat the same sensation as the evaporation of ether on the surface of the body. Mr. Butler satisfied himself that as far as he had observed all the seemingly peculiar conditions and places where the ice has been found do not indicate any other causes when carefully investigated than those of the seasons of the year, and that the ice was formed by no other cause than the natural cold of winter. Professor Cranmer, in 1899, added some important contributions to our knowledge of freezing caverns. All his work goes to prove the winter's cold theory, but he has brought out some new details. He found warm and cold periods in the Tablerloch during the winter months. The coldest air sank to the bottom and the air in the cave stratified itself according to its specific gravity and its temperature. During a cold period, the outside air sank into the cave only to the air stratum, whose temperature, from the preceding warm period, was as much higher as that of the outer air, as this had become warmer in sinking to that stratum. The air which enters falls down the slope and displaces an equal volume of air which streams out under the roof. Water will sometimes drip through a crack in winter until that crack freezes up, when the water may then find some other crack to drip through; at this second place a stalagmite may then grow, while at the first place the stalagmite may stop growing and even begin to diminish from evaporation. Ice begins to form, whenever water gets into a cave, if the cave temperature is below 0°; ice begins to melt as soon as the temperature is over 0°.