scribing the stratification of the glacier as a fundamental
feature of its structure, and the so-called dirt-bands as the margins of
the snow-strata successively deposited, and in no way originating in the
ice-cascades. I shall endeavor to make this plain to my readers in the
course of the present article. I believe, also, that renewed
observations will satisfy dissenting observers that there really exists
a net-work of capillary fissures extending throughout the whole glacier,
constantly closing and reopening, and constituting the channels by means
of which water filtrates into its mass. This infiltration, also, has
been denied, in consequence of the failure of some experiments in which
an attempt was made to introduce colored fluids into the glacier. To
this I can only answer, that I succeeded completely, myself, in the
self-same experiments which a later investigator found impracticable,
and that I see no reason why the failure of the latter attempt should
cast a doubt upon the former. The explanation of the difference in the
result may, perhaps, be found in the fact, that, as a sponge gorged with
water can admit no more fluid than it already contains, so the glacier,
under certain circumstances, and especially at noonday in summer, may be
so soaked with water that all attempts to pour colored fluids into it
would necessarily fail. I have stated, in my work upon glaciers, that my
infiltration-experiments were chiefly made at night; and I chose that
time, because I knew the glacier would most readily admit an additional
supply of liquid from without when the water formed during the day at
its surface and rushing over it in myriad rills had ceased to flow.

While we admit a number of causes as affecting the motion of a glacier,
namely, the natural tendency of heavy bodies to slide down a sloping
surface, the pressure to which the mass is subjected forcing it onward,
the infiltration of moisture, its freezing and consequent expansion,--we
must also remember that these various causes, by which the accumulated
masses of snow and ice are brought down from higher to lower levels, are
not all acting at all times with the same intensity, nor is their action
always the same at every point of the moving mass. While the bulk of
snow and ice moves from higher to lower levels, the whole mass of the
snow, in consequence of its own downward tendency, is also under a
strong vertical pressure, arising from its own incumbent weight, and