720 
MK. HOPKINS ON THE THEOEY OE THE MOTION OE GLACIEES. 
junction, must manifestly be enormous. About some such section as O A this pressure 
will begin to be felt, and will be in full operation about A A'. Now considering the 
direct effects which would be produced by the forces acting on the united glacier below 
the section A A' (independently of the effects of transmission), that portion will pre- 
sent precisely the case of longitudinal structure considered in art. 43. The transverse 
pressure, as above remarked, will be enormous, especially along the axis, to which it vrill 
there be perpendicular, and the general structure will be such as is represented in fig. 7, 
and repeated in fig. 11. The maximum pressure at any point in the axial part of the 
glacier will be increased by the mutual action of the two tributaries after their con- 
fluence, required to divert each from its original direction ; and in the marginal parts of 
the great glacier the maximum pressure will be increased by the comparatively large 
value of F. In the region intermediate to the marginal and central portions, the 
pressure will probably be less than in either of those portions, but in the figure it is 
supposed to be sufficient to superinduce a longitudinal structm’e. In this case, however, 
the angle os at any point P would not increase regularly, and the curves in the part of 
the glacier now referred to might present some degree of inflexion. 
According to Dr. Tyndall, the longitudinal character of the veined structure is 
strongly developed, as a general rule, under all considerable central moraines ; and as 
such moraines always originate in the confluence of two glaciers, and present conditions 
similar to those of the Aar, the explanation in all such casea will be precisely similar to 
that above given, assuming the structure to be due to the instantaneous action of the 
forces acting on the mass, and not to transmission. 
52. In the glacier of Talefre the ice-stream is divided by the Jardin into two separate 
currents, as roughly represented in fig. 12, which thus form, in fact, two separate tribu- 
taries to the united glacier which proceeds, below the Jardin, to precipitate itself over 
the ice-fall of Talefre. Principal Foebes appears to have examined the veined structure 
carefully, and describes it as represented in the figure by the fine lines converging to the 
