IN walking over a piece of water-logged ground, I noticed several small shallow pools which had frozen over. A number of rings, more or less parallel to the edges, were visible as in the plan. The water was found to be a couple of inches below the top of the ice, and the rings were vertical planes, along which the ice could be readily broken. Beneath each of these concentric “joints” the bulb formation indicated in the section (roughly to scale) was found in various stages of development, the bulbs nearest the centre being, as a rule, the most perfectly developed. The full bulb projected about three-quarters of an inch below the ice-sheet, which did not vary much from five-eighths of an inch or so in thickness.