246 Prof. Huxley on the Structure of Glacier Ice. 
detailed by M. Agassiz in (6); and I must frankly confess I 
do not understand how such changes as those described are re- 
concileable with the commonest properties of ice and air. How 
do the bubbles enlarge when exposed to the sun? M. Agassiz has 
already admitted that the chambers are closed (1), and we know 
that ice is not readibly distensible ; and therefore I hold it to 
be impossible that the bubbles should visibly dilate before 
the melting of the adjacent ice; and as to enlarging by the 
melting of the ice-wall, the fractional difference between the 
volume of water and the ice from which it proceeds, would be 
wholly imperceptible on such a scale. With regard to the ex- 
planation of the crackling noise given in (3), 1 can only say 
that I have repeatedly watched a thin lamina of ice melting, 
both by transmitted and reflected light, and that I have seen 
the walls of the chambers reduced to the thinnest pellicle with- 
out being broken by pressure from within. The air-bubbles 
escape quite quietly as soon as their wall is perforated. Further- 
more, the cavities left where the air-bubbles have been, are not 
fissures at all, but, as I have said above, rounded pits. Indeed, 
this is a necessary consequence from M. Agassiz’s own state- 
ments with regard to the shape of the bubbles. 
M. Agassiz affirms in (5), that ice brought up from a depth 
of 65 metres was perfectly similar in structure to that repre- 
sented in his figure 10. The fact is important ; but surely it 
alone affords sufficient evidence that “ diathermanicity” has 
nothing to do with the formation of the cavities and their watery 
contents. And indeed in (4) this same piece of ice (fig. 10) 
is said to have come from the “ gallery of infiltration,” a cavity 
perfectly shaded, and bored many feet below the surface of the 
glacier. So that either this figure does not represent the struc- 
ture of the glacier at this point, or the structure is unaltered, 
and diathermanicity has nothing to do with it. 
It follows, therefore, that there is no evidence to show that 
the influence of solar radiation has anything to do with the 
structure; on the contrary, M. Agassiz’s facts strengthen my 
case. 
If it be the universal character of glacier ice to be full of 
closed cavities containing fluid water and air, it becomes a matter 
of extreme interest to ascertain how the air and the water come 
there ; how it is that the water retains its fluidity, and how it 
is that the water-chambers are compressed. It may seem a 
common-place comparison, but the ice and its cavities contain- 
ing water remind me of nothing so much as a Gruyére cheese, 
in which one so often meets with closed cavities containing fluid 
and air. Let the Névé represent moist curds and the glacier 
valley the cheese-press, and the analogy is perhaps closer than 
