CAUSE OF VARIATIONS 
III 
There is, therefore, a temperature of ocean water which 
is more favorable for the development of glaciers in the 
coastal mountains than a higher or lower temperature. 
But this temperature is not the same for all parts of the 
coastal belt; it must vary with local topographic charac¬ 
ters. The glaciers of a low range may be more sensitive 
to variations of the snow-line than those of a high 
range. Glaciers facing the sea may be more sensitive 
to the variations of wastage dependent on the tempera¬ 
ture of the incoming winds than are glaciers facing the in¬ 
terior. Glaciers fed from cirques, where snow is concen¬ 
trated by wind and avalanche, may respond to variations 
of precipitation in a very different way from glaciers fed 
by open neve fields, where much of the annual snowfall is 
dissipated by dry evaporation. The laws of variation for 
high-grade glaciers may be quite different from those for 
glaciers of gentle slope. And so, when the ocean tem¬ 
perature approximates the value most favorable for the 
development of glaciers in the district as a whole, it will 
be too warm for the highest development of certain gla¬ 
ciers and glacier systems and too cool for others. And 
whenever such a condition obtains, a change in ocean 
temperature will cause some glaciers to enlarge and 
others to contract. 
It is of course impossible that one of the meteorologic 
conditions determining Alaskan glaciation should vary by 
itself while all other conditions remain constant, and the 
case assumed for the sake of illustration is therefore 
purely ideal. It has served its purpose if it has given 
plausibility to the suggestion that a change in some 
meteorologic factor or factors may result in simultaneous 
modifications of glaciers which differ not only in amount 
but in algebraic sign. 
Whatever may be the causes of the variations of gla¬ 
ciers, Alaska affords an inviting field for their investiga- 
