“90 Prof. Forbes on a Remarkable Structure observed 
vation ; and in several glaciers which I have visited, the obser- 
vation of the convolutions of the veined structure is very diffi- 
cult and obscure. Before quitting the subject, I must add an 
observation which I made on the Glacier of the Rhone, and 
which I am preity confident is well founded. The lines of 
fissure, or crevasses, are alivays perpendicular to the conical 
surfaces of the veined structure. ‘These fissures are denoted 
in the figure by the full lines aaa. Perhaps the primary cause 
of these fissures is, that the pressure of the ice at C forces the 
glacier to distend itself into continually widening rings, which 
its rigidity resists, and therefore it becomes traversed by radial 
crevasses. 
The veined structure itself, I have already said, arises from 
the alternation of more or less compact bands of ice. The 
breadth of these varies from a small fraction of an inch to se- 
veral inches. The more porous of these bands are the likeliest 
vehicles for the transmission of water from the higher to the 
lower part of a glacier ; and that opinion receives some con- 
firmation from the fact, that, at a certain depth, in crevasses, 
we may see the veined structure marked out and exaggerated 
by the frozen stalagmite which is protruded from the section 
of the more porous layers. 
In conclusion (for the present), this structure deserves the 
attention of geologists generally, as shewing how the appear- 
ance of the most delicate stratification, and of sedimentary de- 
position, may be produced in homogeneous masses, where no- 
thing of the kind has occurred. For a short time, indeed, I 
was of opinion that this structure resulted from true stratifi- 
cation ; but acloser examination of the mass convinced me 
that, inexplicable as the fact remains, it must be accounted 
for in some other way. We have endeavoured to shew an 
empirical connection which appears to exist between the struc- 
tural planes and the sustaining walls of the glacier, and like- 
wise that the recurrence of congelation and thaw appears to 
strengthen the formation of the bands. But this cannot be 
considered as in any degree amounting to an explanation. 
The analogous difficulty of slaty cleavage in rocks, presents 
itself as not improbably connected with a similar unknown 
cause, whose action pervaded the mass of the crystallizing 
