222 ICE ITS FORMS AND FUNCTIONS. 



reaches a certain limit in summer, and a little beyond that 

 limit in winter ; but still there is a limit at which it melts 

 away and disappears, leaving its terminal mound of rounded 

 blocks and shingly debris. In higher latitudes, however, 

 such as Spitzbergen and Greenland, the ice-sheet that envel- 

 opes the land comes down to the sea-shore, and, ever urged 

 forward by the formation of newer ice inland, even projects 

 its icy wall far into the sea. But being lighter than water, 

 there is a limit beyond which the mass, thick and heavy as it 

 may be, cannot pass, and then it becomes buoyant, is broken 

 off by storms, and drifted by winds and tides and currents 

 as the iceberg over the surface of the deeper ocean. It is 

 thus that the glacier, whether disappearing on the slopes of 

 the mountain or melting away in the ocean, fulfils the beau- 

 tiful saying of De Boue, that " it begins in the clouds, is 

 formed by the mountains, and ends in the ocean." These 

 icebergs or ice-mountains are often of gigantic size, being 

 several miles in circumference, and rising 50, 100, or 200 

 feet above the water.* And when it is borne in mind that 



* The icebergs of the antarctic seas are generally larger, more preci- 

 pitous, and more tabular in form than those of the arctic ; while those 

 of the latter, on the other hand, are more heavily laden with boulders, 

 shingle, and land-worn debris. Sir James Eoss thus adverts to some of 

 the former : " To-day (Jan. 31, 1841) several icebergs were seen ahead 

 of us. They were chiefly of the tabular form, perfectly flat on the top, 

 precipitous in every part, and from 150 to 200 feet high. They had 

 evidently, at one time, formed part of the barrier (the great ice-barrier 

 that prevented his approach to the southern pole, and which was es- 

 timated at more than 1000 feet in thickness), and I felt convinced, from 

 finding them at this season so near the point of their formations, that 

 they were resting on the ground. The lines were immediately prepared, 

 and when we got amongst them next morning we hove - to, and ob- 

 tained soundings in 1560 feet, on a bottom of stiff green mud, leaving 

 no doubt on our minds that all the bergs about us, after having broken 

 away from the barrier, had grounded in this curious bank, which, 

 being two hundred miles from Cape Crozier, the nearest known land, 

 and about sixty from the edge of the barrier, was of itself a discovery 

 of considerable interest," 



