Mr. J. Ball on the Structure of Glaciers. 485 
other, and gradually, owing to diminished motion in front, the 
parts of the ice become pressed together again into a compact 
whole; but in the whole process there is no disturbance of the 
relative position of adjoining portions of the same mass of ice, 
nor anything to affect the internal arrangement of its parts. 
The effect has been exactly the same as if great wedges had 
been cut out of the surface, and the sides of the trenches so 
formed forced together under great pressure. Professor Tyndall 
has shown us how under such circumstances the surfaces brought 
into contact become absolutely welded together. 
Anticipating some of what I have to say on the veined struc- 
ture, I may observe that I this year noticed on the glacier of 
La Brenva, near Cormayeur, what I believe to be direct evidence 
of the process above described. 
In a part of the glacier where the veined structure is parti- 
cularly well marked, I observed two transverse, almost vertical 
bands of very clear blue ice about an inch and a half in thick- 
ness, cutting the planes of veined structure pretty nearly at 
right angles, and inclined to each other at an acute angle. In 
the three portions of ice lying between the transverse bands, 
and at cither side of them, respectively, the planes of the veined 
structure were not conformable but slightly inclined at obtuse 
angles. The cohesion between the ice of the transverse bands 
and that of the veined structure was quite perfect, so that I was 
able with ease to detach hand specimens, in which, if they could 
have been preserved, the unequal inclination of the veined 
structure on either side of the transverse band would have re- 
mained distinctly visible. 
It seems to me clear that in this case the two transverse 
bands represented former crevasses which had been closed to- 
gether late in the autumn, when the increasing cold was suffi- 
cient to freeze the enclosed water before the junction of the 
opposite walls had been quite completed. Such crevasses must 
at one time have been of considerable width, or else the planes 
of the veined structure at opposite sides of the transverse bands 
would not have been inclined, and the appearance would have 
been merely that of a fault in parallel strata. 
Such an appearance may not be rare, but as I had never 
observed it before, and have not seen it noticed by glacier 
writers, I have been a little particular in describing it. Lines 
indicating closed crevasses are common enough, and can some- 
times be traced far on the surface of the glacier ; perhaps, if 
attention be given to the point, it will be found that they often 
correspond to a shifting of the planes of the veined structure. 
2. The veined structure of the middle and lower part of the 
great glaciers, and, more or less, of all glaciers in which the 
