Ice, when rapidly dissolved, continues solid as long as any remains, but, when exposed to the air, at a temperature of only two or three degrees above the freezing point, its solution is effected in a very peculiar manner. Thus, a large lump of fresh-water-ice, when acted on by such a process, if placed in the plane of its formation, resolves itself into considerable columns of a prismatic appearance. These columns are situated in a perpendicular position, almost entirely detached, so that when a blow is struck with an axe, the whole mass frequently falls to pieces. In the land icebergs, these columns are often of amazing magnitude, so as, when separated, to form floating icebergs. All the ice floating in the sea is generally rough and uneven on the surface, and during the greater part of the year covered with snow. Even newly-formed ice, which is free from snow, is so rough and soft that it cannot be skated upon. Under water the colour of the ice varies with the colour of the sea; in blue water it is blue, in green water it is green, and of deeper shades in proportion to its depth. In the thickest olive-green coloured water, its colour, far beneath the surface, appears brownish. A description of the process of freezing from its commencement may now be attempted. The first appearance of ice, when in a state of detached crystals, is called by the sailors _sludge_, and resembles snow when cast into water that is too cold to dissolve it. This smooths the ruffled surface of the sea, and produces an effect like oil in preventing breakers. These crystals soon unite, and would form a continuous sheet, but, by the motion of the waves, they are broken in very small pieces, scarcely three inches in diameter. As they strengthen, many of them coalesce, and form a larger mass. The undulations of the sea still continuing, these enlarged pieces strike each other on every side, whereby they become rounded, and their edges turn up, whence they obtain the name of _cakes_, or _pan-cakes_. Several of these again unite, and thereby continue to increase, forming larger flakes, until they become perhaps a foot in thickness, and many yards in circumference. Every larger flake retains on its surface the impression of the smaller flakes of which it is composed, so that when, by the discontinuance of the swell, the whole is permitted to freeze into an extensive sheet, it sometimes assumes the appearance of a pavement. But when the sea is perfectly smooth, the freezing process goes on more regularly, and probably more rapidly. During twenty-four hours’ keen frost, the ice will become an inch or two in thickness, and in less than forty-eight hours’ time capable of sustaining the weight of a man. Both this kind, and cake-ice, are termed bay-ice. In every opening of the main body of ice at a distance from the sea, the water is always as smooth as that of a harbour; and in low temperatures, all that is necessary for the formation of ice is still water.