ICEBERG, a floating mass of ice broken from the end of a glacier or a polar ice-sheet. Icebergs drift according to the direction of the sea currents, frequently from the polar regions to navigable waters, and they are therefore occasionally en countered far beyond the polar regions. When a glacier de scends to the sea and is pushed outwards into water of greater depth than the thickness of the ice, the ends are broken off and the detached masses float away as icebergs. Only one ninth of the mass of ice is seen above water. Many bergs are overturned, or at least tilted, as they set sail, as the result of the wave-cutting and melting which disturb their equilibrium. The disintegration of an Arctic ice-sheet is a simpler matter, as the ice is already floating. The ice-sheet cracks at the end, and masses break off, owing to the upward pressure of the water upon the lighter ice. This is accomplished with consider able violence. Icebergs, especially those of glacier origin, carry a load of debris which they gradually strew upon the sea floor; glacial material found in dredgings shows that icebergs occa sionally transport their load for a considerable distance.