88 Prof. Forbes on a Remarkable Structure observed 
taining walls of the glacier, distant at least half a mile. Near 
the inferior extremity, where the declivity becomes rapid, the 
structure varies its position in a manner very difficult to trace 
satisfactorily. There can be little doubt, however, that the 
nearly horizontal bands which appear on the steep declivity of 
the glacier at its lower termination, are nothing else than the 
outcropping of these bands, which have there totally changed 
their direction, being transverse instead of longitudinal, and 
leaning forwards in the direction in which the glacier moves 
at a very considerable angle. The ice in this part of the gla- 
cier is distinctly granular, being composed of large fissured 
morsels, nicely wedged together; and the ribboned structure 
is greatly obscured. There seems no doubt, howeyer, that the 
horizontal stratification in the lower part of glaciers, insisted 
on by several writers, is merely a deception arising from this 
cause, so familiar to the geologist who gets a section perpen- 
dicular to the dip of strata, which therefore appear horizon- 
tal. Towards the sides or walls of the glacier, at its lower ex- 
tremity, the veins have their plane twisted round a vertical 
axis, having now their dip towards the centre of the glacier, 
and rising against the walls; and this inclination sometimes 
extends nearly to the axis of the glacier, or the medial moraine, 
where I have observed the veins deviating from the vertical 
by an angle of about twenty degrees, the bands inclining from 
the centre (or rising towards the walls), as if the pressure 
arising from the superior elevation of the glacier under the 
moraine had squeezed them out. The whole phenomenon has 
a good deal the air of being a structure induced perpendicu- 
larly to the lines of greatest pressure, though I do not assert that 
the statement is general. Whilst the glacier is confined be- 
tween precipitous barriers with a feeble inclination, the struc- 
ture is longitudinal. As the glacier, by its weight, falls over 
the lower part of its bed, and moulds itself into the form which 
the continued action of gravity on its somewhat plastic struc- 
ture impresses, the longitudinal structure is first annihilated 
(for throughout a certain space we could detect no indications 
of one kind or other), and the bands then reappear in a trans- 
verse direction, as if generated by the downward and forward 
pressure, which, at the lowest part of the glacier, replaces the 
