2l8 ALASKA GLACIERS 



were largest, but the case is not strengthened by the pres- 

 ence of the sea in the glacier channels. 



RIVERS OF ICE AND OF WATER 



The resemblance which glaciers of the alpine type bear 

 to streams of water, has impressed all observers, and it 

 includes so many details of form and work that the phrase 

 ' river of ice ' seems more than a mere figure of speech. 

 The fact that resemblances arrest attention, of course im- 

 plies that there are also differences ; the contrast between 

 the two materials, ice and water, is so extreme that cor- 

 respondences in their behavior are unexpected and there- 

 fore striking. If we disregard this fundamental difference 

 in material and restrict attention to other causes controlling 

 the phenomena, then we may say that some of the re- 

 semblances between glaciers and rivers are of the nature 

 of homologies, in that the causes of the corresponding 

 features are like, and other resemblances are of the nature 

 of analogies, in that the causes are unlike. Before attempt- 

 ing a classification of resemblances on these lines, I shall 

 enumerate the features of alpine glaciers which have been 

 regarded, or which seem worthy of regard, as correspond- 

 ing to similar features of rivers. 



Resemblances. (i) Upland precipitation is gathered 

 into streams which flow down the slopes. (2) As they 

 flow they meet and join together, forming greater streams, 

 which follow the main valleys or gorges. (3) Sometimes 

 a stream parts against a prominence and reunites beyond 

 it, thus surrounding an island (nunatak); (4) sometimes 

 the parted members proceed independently, as distribu- 

 taries. (5) All parts of the stream are subject to gain 

 and loss of material. In an upper division gain is in 

 excess; in a lower division, loss. In complete examples 

 the maximum volume is in mid-course, and the stream 

 ends distally by complete dissipation. (6) If the stream 



