GLACIERS AND ICEBERGS. 337 



and, by filling up the accidental holes or crevices, it 

 renders the whole structure compact and uniform. 

 Meanwhile the principle of destruction has already be- 

 gun its operations. The ceaseless agitation of the sea 

 gradually wears and undermines the base of the icy 

 mountain, till at length, by the action of its own accu- 

 mulated weight, when it has perhaps attained an alti- 

 tude of a thousand or even two thousand feet, it is torn 

 from its frozen chains, and precipitated, with a tremen- 

 dous plunge, into the abyss below. This mighty launch 

 now floats like a lofty island on the ocean ; till, driven 

 southwards by winds and currents, it insensibly wastes 

 and dissolves away in the wide Atlantic. Icebergs have 

 been known to drift from Baffin's Bay to the Azores. 



Such is believed to be the real origin of the icy 

 mountains or icebergs, entirely similar in their formation 

 to the glaciers which occur on the flanks of the Alps and 

 the Pyrenees. They consist of a clear, compact, and 

 solid ice, having the fine green tint, verging to blue, which 

 ice or water, when very pure and of a sufficient depth, 

 generally assumes. From the cavities of these icebergs 

 the crews of the northern whalers are accustomed, by 

 means of a hose or flexible tube of canvas, to fill their 

 casks easily with the finest and softest water. 



The projecting tongues of the glaciers are not dis- 

 solved where they extend into the sea, but broken off 

 by a species of "flotation. 73 Heavy spring-tides are 

 driven into the head of the bay, and up the fiords, by 

 strong southerly winds ; and the buoyant ice is heaved 

 up by the rising water, and broken off from its parent 

 stream. The floating power of large masses of ice must 

 be enormous. Dr. Sutherland observed upon a small 

 island, at an elevation of forty feet, a block of granite 

 that measured sixteen feet in length, and must have 



contained <it least one hundred and eighty-six tons of 

 22 



