But the most interesting fact about these caves is that, while the shallower one is a glacière, the bigger and deeper one is not. This is situated about ten meters north of the glacière and the direction of the entrance is about the same. Mr. Williams has found snow and ice in May in the entrance pit as far as the daylight goes, but none beyond. I am inclined to think that the explanation of this is the fact that the cave is a _ganghöhle_ or tunnel cave. Mr. Williams described it as a narrow passage with chambers, and at least a hundred meters long, and fifty meters in depth below the surface. The cold air sinks in a certain distance, but as the passage is narrow and long, and too winding for any strong draughts, the cold air which enters is soon neutralized by the supply of warmer air within and by contact with the rocks. I cannot help thinking that it is by some such explanation that we must hope to solve the problem of why certain caves are glacières and others in the immediate neighborhood normal caves; and the caves near Williamstown are exceptional in presenting the problem so patently. PART II. THE CAUSES OF SUBTERRANEAN ICE. THE CAUSES OF SUBTERRANEAN ICE. I. _Terminology._--Ice enduring the entire year is found, in temperate latitudes, in a variety of forms and in several different kinds of places. In some cases it is entirely above the surface of the earth; in others it is entirely beneath the surface of the earth. These are the extremes, and between them there are certain intermediate forms. The perennial ice above ground of temperate regions has gradually become known in English by the French word _glacier_, but strange to say, there is no term in use in English which accurately describes the perennial ice formations which are partially or completely underground. Thus the term "ice cave" is applied to a rock cavern containing ice, and the term "ice gorge" to a rock gorge containing ice. Both terms are misleading, because the character of the contents is mentioned before the nature of the geological formation. We say correctly enough "limestone cave" or "lava cave" and, in my opinion, we should apply the term "ice cave" in a similar manner to the hollows in the ice at the lower end of glaciers, whence the glacier waters make their exit. These are really "ice caves," that is caves with sides and roof made of ice. Another trouble of the term "ice cave," as applied to rock formations containing ice, is that it is not generic: not only is it incorrect, but also it is not comprehensive. It does not apply to mines, tunnels, wells, gullies, boulder taluses, or underground ice sheets. If "ice cave" is used, except in its true sense of glacier ice cave, it seems at least as though it should be so only for real caves which retain ice, as opposed to taluses and wells. Curiously enough, the Germans are just as inaccurate as ourselves, for their terms _eishöhle_ and _eisloch_ are absolute translations of our "ice cave" and "ice