278 
INTERNAL STRUCTURE AND 
ded to, that, while the surface of the glacier loses 
annually from nine to ten feet of its thickness by 
evaporation and melting, it swells, on the other 
hand, in the spring, to the amount of about five 
feet. Such a dilatation can hardly be the re- 
sult of pressure and the packing of the snow and 
ice, since the difference in the bulk of the ice 
brought down, during one year, from a point 
above to that under observation, would not ac- 
count for the swelling. It is more readily ex- 
plained by the freezing of the water of infiltration 
during spring and early summer, when the in- 
filtration is most copious and the winter cold 
has been accumulating for the longest time. 
This view of the case is sustained by Elie de 
Beaumont, who states his opinion upon this point 
as follows : — 
“ Pendant l’hiver, la temperature de la surface 
du glacier s’abaisse a un grand nombre de degr^s 
au-dessous de zero, et cette basse temperature 
penetre, quoique avec un affaiblissement graduel, 
dans l'interieur de la masse. Le glacier se fen- 
dille par l’effct de la contraction resultant de 
ce refroidissemont. Les fentes restent d’abord 
vides, et concourent au refroidissement des gla- 
ciers en favorisant l’introduction de Pair froid ex- 
terieur ; mais au printemps, lorsque les rayons 
du soleil echauffent la surface de la neige qui 
couvre le glacier, ils la ramenent d’abord a zero, 
