Page:Polar Exploration - Bruce - 1911.djvu/65

Rh against a rocky shore, get broken up into thousands of pieces only a few feet in diameter. This broken-up ice is known as "Pack ice." During the breaking up of the ice, the floes crush together and their edges are broken and curled and piled with the pressure. Farther away from the open sea, well in among the solid floes, this pressure is very heavy and one floe may run over and another under the other. The edges of an extended crack, that has formed in a weak place, curl over and over and a long ridge of broken-up ice is the result. These ridges are known as "Pressure ridges," and the irregular piles of ice of which they are formed, or similar piles of ice formed along the edges of smaller free-floating floes, or the piles of ice that are formed by the pieces of pack ice that get heaped upon each other are known as "Hummocky ice" or simply "Hummocks."

This irregular conglomeration freezes together again almost immediately if it is winter, and indeed it needs very tempestuous sea and weather conditions to break up the solid continuous floe in winter. The usual time of break-up is in the spring, when with rising temperatures the sea ice is becoming rotten.

"Brash ice" is ice that is usually met with on the outskirts of the pack. It is the remnant of the fray, being composed of a chaotic