CHAP. II.] ICEBERGS. 39 



To explain how the bodies and skeletons of these inhabitants 

 of the deep, whether found entombed or not in ice, were carried 

 up to considerable heights above the level of the sea, appeared to 

 me at first more difficult than to account for their having been 

 included in solid ice. A few months after my visit to Ports 

 mouth I saw Captain Wilkes, of the United States Exploring 

 Expedition, and called his attention to the problem. He 

 remarked, that the open sea sometimes freezes round the Sand 

 wich Islands, so that ships can not approach within 100 miles 

 of the shore. In like manner, in Antarctic regions, the ocean 

 often freezes over the base of a cliff formed of barrier ice. In 

 all these cases, the sheet of ice, however continuous, does not 

 adhere to the land or the barrier, because the rise and fall of the 

 tide, however slight, causes a rent, permitting the whole mass to 

 move up and down. The snow, drifting off the land in vast 

 quantities during winter, falls over the cliffs upon the frozen 

 surface of the sea, until its weight is such that it causes the 

 whole mass to sink ; and unless the winds and currents happen 

 to float it off, it may go on subsiding till it acquires a great 

 thickness, and may at last touch the bottom. Before this hap 

 pens, however, it usually gets adrift, and, before it has done 

 melting, tumbles over or capsizes more than once. 



On my return to England, in 1846, I described the same 

 phenomena to my friend Dr. Joseph Hooker, and subsequently 

 to Sir James Ross, and they both of them, without hearing 

 Captain Wilkes s theory, suggested the same explanation, having 

 observed that a great sheet of ice had formed in the sea by the 

 freezing of melted snow on the southern or polar side of every 

 Antarctic island. If the carcass of a dead whale be thrown up 

 on this ice, it must soon be buried under other snow drifted from 

 the land, and will at length be inclosed in the lower part of an. 

 iceberg, formed in the manner before described. The frequent 

 overturning or reversal of position of these great masses, arises 

 from the temperature of the water at the depth of 1000 or 1500 

 feet, to which they frequently descend, being much warmer than 

 the incumbent air or more superficial water. When the inferior 

 or submerged portions melt, the center of gravity is soon changed 



