PROGRESSION OF GLACIERS. 
241 
this connection. I will only state, that, so far 
as my own observation goes, the movement of 
the glacier is most rapid where the greatest 
amount of moisture is introduced into the mass, 
and that I believe there must be a direct relation 
between these two facts. If I am right in this, 
then the motion, so far as it is connected with 
infiltrated moisture or with the dilatation caused 
by the freezing of that moisture, will, of course, 
be most rapid where the glacier is most easily 
penetrated by water, namely, in the region of 
the neve and in the upper portion of the glacier- 
troughs, where the neve begins to be transformed 
into more or less porous ice. This cause also 
accounts, in part at least, for another singular 
fact in the motion of the glacier: that, in its 
higher levels, where its character is more porous 
and the water entering at the surface sinks read- 
ily to the bottom, there the bottom seems to 
move more rapidly than the superficial parts of 
the mass, whereas, at the lower end of the glacier, 
in the region of the compact ice, where the in- 
filtration of the water at the bottom is at its min- 
imum, while the disintegrating influences at the 
surface admit of infiltration to a certain limited 
depth, there the motion is greater near the sur- 
face than toward the bottom. But, under all 
circumstances, it is plain that the various causes 
producing motion, gravitation, pressure, infiltra- 
11 r 
