somewhat lower temperature than the mean temperature of the place where the cave occurs." Browne noticed prismatic ice several times. He says of it: "M. Thury suggests also, as a possibility, what I have found to be the case by frequent observations, that the prismatic ice has greater power of resisting heat than ordinary ice. * * * A Frenchman who was present in the room in which the Chemical Section of the British Association met at Bath, and heard a paper which I read there on this prismatic structure, suggested that it was probably something akin to the rhomboidal form assumed by dried mud; and I have since been struck by the great resemblance to it, as far as the surface goes, which the pits of mud left by the coprolite workers near Cambridge offer, of course on a very large scale. This led me to suppose that the intense dryness which would naturally be the result of the action of some weeks or months of great cold upon subterranean ice might be one of the causes of its assuming this form, and the observations at Jena would rather confirm than contradict this view: competent authorities, however, seem inclined to believe that warmth, and not cold, is the producing cause." Mr. Browne found a hollow cone at La Genollière, for which he accounted as follows: "In the loftier part of the cave * * * ninety six drops of water in a minute splashed on to a small stone immediately under the main fissure. This stone was in the centre of a considerable area of the floor which was clear of ice. * * * I found that the edge of the ice round this clear area was much thicker than the rest of the ice on the floor, and was evidently the remains of the swelling pedestal of the column. * * * When the melted snows of spring send down to the cave, through the fissures of the rock, an abundance of water at a very low temperature and the cave itself is stored with the winter's cold, these thicker rings of ice catch first the descending water, and so a circular wall, naturally conical, is formed around the area of stones; the remaining water either running off through the interstices, or forming a floor of ice of less thickness, which yields to the next summer's drops. In the course of time, this conical wall rises, narrowing always, till a dome-like roof is at length formed and thenceforth the column is solid." From what I have observed myself, this explanation seems to fairly meet the facts. Professor T. G. Bonney, in 1868, was inclined to believe that there was some connection between glacières and a glacial period.