1881 .] 
163 
[Shaler. 
a good deal of surprise has been expressed that no correspon- 
dence has been found between these weather observations and 
the advance or recession of the several glaciers. If the reader 
will consider the following study of glacial conditions, he will, I 
hope, see that this failure to connect climatal changes and ice 
movements is not at all a proper matter for surprise. 
A glacier consists of two sections, an ill defined upper region 
of eternal snow, generally termed neve, and a distinctly limited 
protrusion of ice in the form of a tongue which descends the val- 
ley for a greater or less distance beyond the line of perpetual 
snow. Although the relation between these two sections is well 
known, the phenomena of glaciers are so out of the line of com- 
mon experience, that it is not easy to keej:> them well in mind. 
Therefore let us notice the fact that this neve region is the col- 
lecting ground of all the material that pours into the ice river. 
Whoever can recall the aspect of these regions, as they appear 
when seen from some point that commands a view both of the 
neve and its tongues of ice, will appreciate the great disproportion 
between the area of these fields of snow qnd the ice streams that 
flow from them. Generally these snow fields cover many times 
the area of the streams of ice that drain them. The move- 
ment of the glacial matter in these fields of perpetual snow is 
very slow indeed, much slower than in the well defined ice streams 
towards which they tend. We cannot regard the average rate of 
movement as more than about two inches 2^1* day. At this rate, 
if the snow fields extended two miles beyond the head of the 
glacier proper, it would require about one hundred and fifty years 
for the snow from the farthest part of the neve to work down 
into the glacier proper. If the glacier had a length of six miles, 
and its average rate of movement was one foot a day, nearly 
another hundred years would be required to bring a particle of 
snow that fell upon the upper part of the neve, down to the end 
of the glacier ; so that the snow that fell on the upper j)art of the 
neve regions in the early part of the seventeenth century would 
be just now appearing at the end of the ice stream. 
The rate of flow from the neve into the glacier proper depends, 
in part, upon the depth of snow accumulated upon the upper fields. 
If a succession of snowy winters accumulates the glacial matter, 
