Prof. Huxley on the Structure of Glacier Ice. 245 
to 65 metres. I observed, besides, that in the fragments which 
proceeded from a great depth, all the bubbles without exception 
were strongly flattened, whilst at less depths there were some 
less compressed and even altogether round, as at the surface. 
“Tt follows, hence, that a strong pressure is exercised in the 
interior of the glacier.”—P. 167. 
(6) “TI ought also to mention a singular property of these 
air-bubbles, which at first was very surprising, but afterwards 
admitted of very satisfactory explanation. When a fragment 
containing air-bubbles is exposed to the actlon of the sun, the 
bubbles insensibly enlarge. Soon, in proportion as they enlarge, 
a transparent drop shows itself on some point of the bubble. 
This drop in enlarging contributes its share to the enlargement 
of the cavity, and as it progresses it predominates over the 
air-bubble. The latter then swims in the midst of a zone of 
water, and incessantly tends to reach the most elevated point, at 
least if the flatness of the cavity does not hinder it.”—Pp. 167, 
168. 
(7) In a note appended to this passage, M. Agassiz speaks 
of the irregularity of the walls of some of the bubbles, and adds, 
“ The same effect has been produced upon the bubbles of the 
fragment fig. 10. There also all the bubbles have enlarged by 
diathermanicity, and a little drop has developed in the middle of 
each. But as the cavities are very small, the drops do not yet 
move freely in their cavity.” 
It will be observed that in Nos. 1, 4,5, 6, M. Agassiz con- 
founds together the water-chambers and the air-bubbles under 
the common term of “ bubbles,” and he affirms (6) that the pre- 
sence of water in the “ air-bubbles” is the effect of exposure to 
the sun’s rays, and of the different diathermanicity of air and ice*. 
A careful analysis of M. Agassiz’s facts, however, is very in- 
structive. In the first place, I recognize in his fig. 10. pl. 6, a 
fair, though rough and sketchy, representation of the general 
arrangement and form of the water-chambers with their con- 
tained air-bubbles. The chambers are as usual flattened, but 
the artist has rightly represented their contained air-bubbles as 
spheroidal. The strangest thing is, however, that M. Agassiz 
has taken the air-bubbles for drops of water, and the drops of 
water for air-bubbles, as any one who is familiar with the mi- 
croscopic appearance of bubbles of air will see, on comparing the 
description in (7) with the figure 10. In the next place, I re- 
peatedly exposed thin plates of ice to the sun, carefully watching 
the air-bubbles, without being able to observe the phenomena 
* The Messrs. Schlagintweit (Untersuchungen, p.17)adopt Prof. Agassiz’s 
views on this point, and with him regard the presence of water as a local 
and partial phenomenon. 
