EXTERNAL APPEARANCE OF GLACIERS 295 
feet of rods with me, and again I was foiled. 
Eventually I succeeded in carrying up a thou- 
sand feet of line, and satisfied myself, after many 
attempts, that this was about the average thick- 
ness of the glacier of the Aar, on which I was 
working. 
I mention these failures, because they give 
some idea of the discouragements and difficulties 
which meet the investigator in any new field of 
research ; and the student must remember, for 
his consolation under such disappointments, that 
his failures are almost as important to the cause 
of science and to those who follow him in the 
same road as his successes. It is much to know 
what we cannot do in any given direction, — the 
first step, indeed, toward the accomplishment of 
wdiat we can do. 
A like disappointment awaited me in my first 
attempt to ascertain by direct measurement the 
rate of motion in the glacier. Early observers 
had asserted that the glacier moved, but there 
had been no accurate demonstration of the fact, 
and so uniform is its general appearance from 
year to year that even the fact of its motion was 
denied by many. It is true that the progress 
of boulders had been watched ; a mass of rock 
which had stood at a certain point on the glacier 
was found many feet below that point the follow- 
ing year ; but the opponents of the theory insisted 
