Page:South - the story of Shackleton's last expedition, 1914-1917.djvu/472

352 tight pack-ice; open ice; bay-ice and brash. With the exception of bay-ice, which is more generally known as young ice, all these terms pass current in the Antarctic.

Slush or Sludge. The initial stages in the freezing of sea-water, when its consistency becomes gluey or soupy. The term is also used (but not commonly) for brash-ice still further broken down.

Pancake-ice. Small circular floes with raised rims; due to the breakup in a gently ruffled sea of the newly formed ice into pieces which strike against each other, and so form turned-up edges.

Young Ice. Applied to all unhummocked ice up to about a foot in thickness. Owing to the fibrous or platy structure, the floes crack easily, and where the ice is not over thick a ship under steam cuts a passage without much difficulty. Young ice may originate from the coalescence of "pancakes," where the water is slightly ruffled or else be a sheet of "black ice," covered maybe with "ice-flowers," formed by the freezing of a smooth sheet of sea-water.

In the Arctic it has been the custom to call this form of ice "bayice"; in the Antarctic, however, the latter term is wrongly used for land-floes (fast-ice, etc.), and has been so misapplied consistently for fifteen years. The term bay-ice should possibly, therefore, be dropped altogether, especially since, even in the Arctic, its meaning is not altogether a rigid one, as it may denote firstly the gluey "slush," which forms when sea-water freezes, and secondly the firm level sheet ultimately produced.

Land floes. Heavy but not necessarily hummocked ice, with generally a deep snow covering, which has remained held up in the position of growth by the enclosing nature of some feature of the coast, or by grounded bergs throughout the summer season when most of the ice breaks out. Its thickness is, therefore, above the average. Has been called at various times "fast-ice," "coast-ice," "land-ice," "bay-ice" by Shackleton and David and the Charcot Expedition; and possibly what Drygalski calls "Schelfeis" is not very different.

Floe. An area of ice, level or hummocked, whose limits are within sight. Includes all sizes between brash on the one hand and fields on the other. "Light-floes" are between one and two feet in thickness (anything thinner being "young-ice"). Those exceeding two feet in thickness are termed "heavy floes," being generally hummocked, and in the Antarctic, at any rate, covered by fairly deep snow.

Field. A sheet of ice of such extent that its limits cannot be seen from the masthead.

Hummocking. Includes all the processes of pressure formation whereby level young ice becomes broken up and built up into