204 EXTERNAL APPEARANCE OF GLACIERS. 
one side and a shallow one on the other, and a 
little heap of loose materials in the bottom. 
They are the sun-dials of the glacier, recording 
the hour by the advance of the sun’s rays upon 
them. 
In recapitulating the results of my glacial ex- 
perience, even in so condensed a form as that in 
which I intend to present them here, I shall be 
obliged to enter somewhat into personal narra- 
tion, though at the risk of repeating what has 
been already told by the companions of my ex- 
cursions, some of whom wrote out in a more pop- 
ular form the incidents of our daily life which 
could not be fitly introduced into my own record 
of scientific research. When I first began my 
investigations upon the glaciers, now more than 
twenty-five years ago, scarcely any measurements 
of their size or their motion had been made. One 
of my principal objects, therefore, was to ascer- 
tain the thickness of the mass of ice, generally 
supposed to be from eighty to a hundred feet, 
and even less. The first year I took with me a 
hundred feet of iron rods, (no easy matter, where 
it had to be transported to the upper part of a 
glacier on men’s backs,) thinking to bore the 
glacier through and through. As well might I 
have tried to sound the ocean with a ten-fathom 
line. The following year I took two hundred 
