68 HOBBS— CHARACTERISTICS OF THE [April 22, 



Differential Surface Melting of the Ice 113 



Moats Between Rock and Ice I^Iasses 117 



Englacial and Subglacial Drainage of the Inland-ice 118 



The Marginal Lakes 118 



Ice Dams in Extra-glacial Drainage 122 



Submarine Wells in Fjord Heads 122 



Discharge of Bergs from the Ice Front 123 



The Ice Cliff at Fjord Heads 123 



Manner of Birth of Bergs from Studies in Alaska 124 



Studies of Bergs Born of the Inland-ice of Greenland 127 



The Arctic Glacier Type. 

 Introduction. — As elsewhere pointed out, continental glaciers are 

 in other than dimensional respects sharply differentiated from those 

 types which have been described as mountain glaciers.^ The ice-cap 

 glacier, while of smaller dimensions than the true inland-ice or the 

 continental glacier, is yet distinctly allied with this type, and has 

 few affinities with mountain glaciers. The sharpness of the dis- 

 tinction has often been overlooked for the reason that true moun- 

 tain glaciers frequently exist within a fringe surrounding the larger 

 areas of inland-ice both in the Arctic and Antarctic regions. The 

 distinguishing difference between mountain glaciers and continental 

 glaciers is one primarily dependent upon the proportion of the 

 land surface which is left uncovered by the ice, and the position 

 of this surface relative to the margins of the snow-ice mass. With 

 true mountain glaciers land remains uncovered above the highest 

 surfaces of the glacier, zvhere, in consequence, a special erosional 

 process — cirque recession — becomes operative. The smaller ice- 

 caps take their characteristic carapace form and cover the surface 

 of the land within their margins, because that surface is relatively 

 level. Had it been otherwise, the same conditions of precipitation 

 would have yielded mountain glaciers in their place. The law 

 above stated is none the less applicable, since because of this flat 

 basement no land projects above their higher levels. - 



^ Wm. Herbert Hobbs, " The Cycle of Mountain Glaciation," Geogr. 

 Jour., Vol. 35, 1910, pp. 147, 148. 



^ With a keenness of insight which has rendered the descriptions of his 

 travels particularly valuable, Sir Martin Conway has pointed out the main 

 distinction here expressed. His explanation of cirque formation, which he 



