288 EXTERNAL APPEARANCE OF GLACIERS. 
to a certain superficial depth, so that its surface 
is covered with a decomposed crust of broken, 
snowy ice, so permeated with air that it has 
a dead- white color, like pounded ice or glass. 
Those who see the glacier in this state miss the 
blue tint so often described as characteristic of 
its appearance in its lower portion, and as giving 
such a peculiar beauty to its caverns and vaults. 
But let them come again after a summer storm 
has swept away this loose sheet of broken, snowy 
ice above, and before the same process has had 
time to renew it, and they will find the compact, 
solid surface of the glacier of as pure a blue as 
if it reflected the sky above. We may see it in 
the early dawn, before the new ice of the preced- 
ing night begins to yield to the action of the sun, 
and the surface of the glacier is veined and in- 
laid with the water poured into its holes and fis- 
sures during the day, and transformed into pure, 
fresh ice during the night, — or when the noon- 
day heat has wakened all its streams, and rivu- 
lets sometimes as large as rivers rush along its 
surface, find their way to the lower extremity 
of the glacier, or, dashing down some gaping 
crevasse or open well, are lost beneath the ice. 
It would seem, from the quantity of water that 
is sometimes ingulfed within these open breaks 
in the ice, that the glacier must occasionally bo 
fissured to a very great depth. I remember once, 
