230 
THE FORMATION OF GLACIERS. 
heights. This region is called the region of the 
nevS. It is properly the birthplace of the gla- 
ciers, for it is here that the transformation of 
the snow into ice begins. The neve ice, though 
varying in the degree of its compactness and 
solidity, is always very porous and whitish in 
color, resembling somewhat frozen slosh, while 
lower down in the region of the glacier proper 
the ice is close, solid, transparent, and of a bluish 
tint. 
But besides the difference in solidity and in ex- 
ternal appearance, there are also many other im- 
portant changes taking place in the ice of these 
different regions, to which we shall return pres- 
ently. Such modifications arise chiefly from the 
pressure to which it is subjected in its downward 
progress, and to the alterations, in consequence of 
this displacement, in the relative position of the 
snow- and ice-beds, as well as to the influence ex- 
erted by the form of the valleys themselves, not 
only upon the external aspect of the glaciers, but 
upon their internal structure also. The surface 
of a glacier varies greatly in character in these 
different regions. The uniform even surfaces of 
the upper snow-fields gradually pass into a more 
undulating outline, the pure white fields become 
strewn with dust and sand in the lower levels 
while broken bits of stone and larger fragments 
of rock collect upon them, which assume a regu- 
