THE GLACIERS OF GREENLAND. 81 



of a semi-fluid stream, the relative amount of friction be- 

 comes very much less, so that it will move more than twice 



Fig. 32.— Map of Frederikshaab Glacier, between 62" and 63°, sbowing course of Lieuten- 

 ant Jensen in 1878 (forty-seven and a half miles). The black part, ice ; white, 

 land : shaded, water ; J. N., Jensen's nunataks ; D. N.. Dolager's nunataks ; white 

 lines on the black, crevasses ; arrows, glacier-flow. Five species of plants were found 

 on the nunataks which still survive on the White Mountains (N. H.). Dana. 



as fast as before. This property of a semi-fluid is made suf- 

 ficiently evident from a homely illustration. Molasses in 

 cold weather will scarcely run at all through a gimlet-hole, 

 while it will run with considerable freedom through an 

 auger-hole. Xow, the glaciers of the Alps, which were the 

 subjects of Professor Tyndall's measurements, were, in com- 

 parison to those in Greenland and Alaska, about in the pro- 

 portion of a small gimlet-hole to a large auger-hole, and the 

 faster motion is really not surprising. 



