EXTERNAL APPEARANCE OF GLACIERS. SOI 
where the stones with angular edges hare left 
their sharp scratches, where sand and gravel have 
rubbed and smoothed the rocky surface, and left 
it bright and polished as if it came from the 
hand of the marble-worker. These marks are 
not to be mistaken by any one who has carefully 
observed them ; the scratches, furrows, grooves, 
are always rectilinear, trending in the direction 
in which the glacier is moving, and most distinct 
on that side of the surface-inequalities facing the 
direction of the moving mass, while the lee-side 
remains mostly untouched. 
It may be asked, how it is known that the gla- 
cier carries this powerful apparatus on its sides 
and bottom, when they are hidden from sight. 
I answer, that we might determine the fact theo- 
retically from certain known conditions respecting 
the conformation of the glacier, to which I shall 
allude presently ; but we need not resort to this 
kind of evidence, since we have ocular demon- 
stration of the truth. Here and there on the 
sides of the glacier it is possible to penetrate 
between the walls and the ice to a great depth, 
and even to follow such a gap to the very bottom 
of the valley ; and everywhere do we find the 
surface of the ice fretted, as I have described it, 
with stones of every size, from the pebble to the 
boulder, and also with sand and gravel of all 
sorts, from the coarsest grain to the finest ; and 
