MUIR GLACIER 
2 3 
was only 1,900 feet. It is therefore probable that the 
summer rate of retreat is much more rapid than the winter. 
While these considerations tend to qualify the figures 
deduced from uncorrected observations, they do not affect 
their general tenor. The application of a correction 
for seasonal oscillation would diminish by a few hun¬ 
dred feet the estimate for the total retreat from 1886 to 
1890, and increase by a similar amount the estimate for 
the total retreat from 1892 to 1899, but would leave un¬ 
changed the general result that the retreat in nineteen years 
has been more than a mile and a half, and that the general 
retreat suffered at least one interruption, a small advance 
occurring between 1890 and 1892. 
The general change of contour mentioned above is of 
peculiar interest because it was predicted by Reid. The 
middle of the glacier ends in deep water, a maximum 
sounding of 720 feet having been recorded, but at each 
side of the rock trough the ice rests on a bank of gravel 
rising above the water level. Observing that the surfaces 
of these gravel banks descend northward beneath the 
glacier, Reid inferred that with the progress of recession 
lanes of sea water would soon be admitted between the 
ice and the gravel; and having determined that the mar¬ 
ginal parts of the glacier advance very slowly as compared 
to the medial, he inferred that their cliffs would be carried 
back with relative rapidity by the attack of the warm sea 
water. As the map shows, these expectations have been 
fully realized. 
In bringing the record of the glacier down to the sum¬ 
mer of 1899 the preceding paragraphs practically close a 
division of its modern history, for a new epoch was intro¬ 
duced only three months after our visit. On the 12th of 
September the southern coast of Alaska was shaken by a 
severe earthquake, and other shocks followed at intervals. 
These greatly modified the condition of its tidal glaciers, 
