Glacier Work. — Scott. 239 
Very little seems to be recorded on this point. The Mont 
Blanc glaciers recently studied by Dr. Reid, however, show 
blue bands well developed, and at the same time show conclu- 
sively that they are independent of stratification. In un- 
weathered sections, he says, it is not difficult to distinguish 
between the blue bands and stratification, though after ex- 
posure to the weather they are so nearly alike that to dis- 
tinguish between them is difficult. 
Study of the Swiss glaciers by Deeley and Fletcher indi- 
cates that the neve when viewed from a distance appears to 
be finely stratified, having layers of blue ice alternating with 
white ones. Such stratification, however, on close examination 
appears to be due wholly to air bubbles imprisoned in the ice. 
And though the granules are known to have their optic axes 
arranged in no definite direction, yet "the lines of bubbles 
traverse the mass in definite layers." These layers of bubbles 
are shown to be the result of alternate melting snow at the sur- 
face, and falling of snow thereupon, thus imprisoning some 
air each time. This air is, of course, subjected to pressure by 
the accumulation of snow, and as the snow changes to neve 
and thence to ice, more or less air will be held between the 
granules. Meteorological conditions would naturally influence 
this volume of enclosed air, and it is found, for example, that 
the ice of the Grindelwald is very pure and blue, as compared 
with that of the Mont Blanc range. A massive ice-sheet, also, 
may have local eddies in its lower portions, the ice moving 
obliquely to the general flow of the main mass, as is well known 
in Greenland where it flows around the isolated Nunataks. * 
It there acquires in some cases, it is said, a beautiful banded 
structure, t 
Erosion. 
The erosive action of a glacier is a very distinguishing 
feature of ice action. The contact and pressure of the ice, 
doubtless aid very materially in dislodging boulders and rock 
material from the mountain surface, but by far the greater 
action is produced by the blocks of rock, stones and sand that 
find their way between the ice and bed over which it moves. 
Such detritus is angular in character and though it becomes 
"Nansen. "First crossinK of Greenland." 
tPlatos 9 anrl U of Paper on Greenland Ice, by E. von Drygals.il, 
Zeitsch. Gesell. f. Erdekunde, Berlin, 1892. 
