DECAY OF ICEBERGS 137 



is treated with any violence. Even when saiHng in a quiet sea 

 the innate tensions of the ice, increased it may be by the 

 changes of temperature to which it lias been subjected since 

 it parted from the parent glacier, now and then cause large 

 fragments to tly from the steep cliffs, to float as satellites 

 of the mass until they melt away. 



The processes of decay acting on the summit of the icebergs 

 reveal in the melting forms the existence of incipient rifts in 

 their masses. Unlike the surface of ordinary ice-sheets, which 

 commonly melt down somewhat evenly, the berg top is made 

 up of irregular pinnacles and chasms, which in the later stage 

 of its existence may take on forms of the utmost variety. 

 The picturesqueness of these floating islands of the north is in 

 large measure due to the exceedingly varied form.^ of their sky 

 lines. The architects of our day, who recognize the striking 

 effects which may be produced in edifices by means of pedi- 

 ments and pinnacles, might win suggestions from a study of 

 these fantastic structures. These indentations of the iceberg 

 top are produced by the same abundant planes of weakness 

 which cause the mass so readily to rend asunder whenever 

 subjected to strains such as may arise from the causes we 

 have considered. The warmth and rain penetrating into these 

 crevices eat the ice away while the less weakened parts 

 remain intact. In the case of many bergs, even when they 

 have been long atioat, the top is not much indented, for the 

 reason that the frequent changes of position have not given 

 the ice time to be affected by exposure to the air. 



In the southern hemisphere, icebergs are limited to the 

 western Atlantic and eastern Pacific, and to the waters of very 

 high latitudes within the Antarctic Circle. They are almost 

 unknown in the North Pacihc, for the reason that the onlv 



