244 Prof. Huxley on the Structure of Glacier Ice. 
bubbles, whilst the interspaces of these bubbles are perfectly 
transparent, so that without being as diaphanous as ordinary 
water-ice, the compact ice has not the opacity of Névé ice. 
Moreover, it is more compact, and what is especially character- 
istic, it presents no trace of granular structure: a fragment 
exposed to the action of heat does not become resolved into 
grains of Névé, but breaks up into angular fragments. 
“This difference of structure is accompanied by a greater 
impermeability ; water no longer traverses the mass with the 
same ease and uniformity, but is seen to follow in preference 
certain angular routes which are the capillary fissures.”—P. 151. 
(2) “ The means employed by nature to maintain this 
amount of plasticity and compressibility in glacier ice is the 
water which circulates throughout the mass, and which, while it 
lubricates it, contributes to maintain within it a constant tem- 
perature during the greater part of the year.”—Pp. 152, 153. 
(3) “ Superficial fissures which must not be confounded with the 
capillary fissures. 
“ When during a fine summer day one travels over the upper 
regions of the compact ice (about the region of the Abschwung, 
on the Aar glacier), a continual crepitation is heard on all sides. 
It is caused by the bubbles of air which on approaching the 
surface escape through the ice, where they have been dilated by 
the effect of diathermanicity, and cause the parietes of the ice to 
burst when they are no longer sufficiently strong to resist the 
dilatation of the air.”—P. 153. 
(4) ** The air-bubbles undergo no less curious modifications. 
In the neighbourhood of the Névé, where they are most nume- 
rous, those which one sees at the surface are all spherical or 
ovoid; but by degrees they begin to be flattened, and near the 
end of the glacier there are some which are so flat, that they might 
be taken for fissures when seen in profile. The drawing, pl. 6, 
fig. 10, represents a bit of ice detached from the gallery of 
infiltration. All the bubbles are greatly flattened. But what 
is most extraordinary is, that, far from being uniform, the flat- 
tening is different in each fragment, so that the bubbles, accord- 
ing to the face which they offer, appear either very broad or very 
thin. I know of no more significant fact than this, since it 
demonstrates that each fragment of ice is capable of undergoing 
in the interior of the glacier a proper displacement independently 
of the movement of the whole.”—P. 167. 
(5) “The same flattening of the bubbles is found at a greater 
depth. While engaged in my boring experiments, I observed 
attentively the fragments of ice brought up to the surface by 
the borer. I found in them almost flat bubbles, perfectly similar 
to those of the fragment figured above, at all depths from 10 
