336 GLACIERS AND ICEBERGS. 



gets narrower and narrower. North of Cape York the 

 ice-stream projects into the sea itself, even beyond the 

 line of prominent headlands. It is from this region that 

 the vast icebergs, drifted out into the open Atlantic by 

 the southward current, are derived ; for it is a singular 

 fact that there is no glacier-ice along the shores west- 

 ward of Lancaster Sound. All the snow which there 

 falls, even so far north as 77 latitude, escapes to the 

 sea in streams of water, carrying with them vast quan- 

 tities of mud and shingle. The land on both sides of Bar- 

 row's Strait is composed of limestone ; but Greenland, 

 and the coasts which form Davis's Strait, Baffin's Bay, 

 and Lancaster Sound, where the fallen snow is retained 

 for ages before it slips, as the solid glacier, back to the 

 ocean, are all made of hard crystalline rock. Dr. Suth- 

 erland thinks that this difference of mineral constitution 

 may in some way affect the temperature, and so deter- 

 mine the abundance of glaciers in the one position, and 

 their absence in the other. 



We may here remark that the ice which obstructs the 

 navigation of the Arctic seas is of two kinds : the one 

 produced by the congelation of fresh, and the other by 

 that of salt water. In those inhospitable tracts, the 

 snow, which annually falls on the islands or continents, 

 being again dissolved by the progress of the summer's 

 heat, pours forth numerous rills and limpid streams, 

 which collect along the indented shores, and in the deep 

 bays enclosed by precipitous rocks. There this clear 

 and gelid water soon freezes, and every successive year 

 supplies an additional investing crust, till, after the 

 lapse, perhaps, of several centuries, the icy mass rises at 

 last to the size and aspect of a mountain, commensurate 

 with the elevation of the adjoining cliffs. The melting 

 of the snow, which is afterwards deposited on such 

 enormous blocks, likewise contributes to their growth ; 



