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 
6 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 
