ds are formed
subsequently, in consequence of the onward progress of the glacier and
the pressure to which it is subjected. The secondary blue bands
intersect the planes of stratification at every possible angle, and may
therefore seem identical with the stratification in some places, while
in others they cut it at right angles. It has been objected to my theory
of glacial structure, that I have considered the so-called blue bands as
a superficial feature when compared with the stratification. And in a
certain sense this is true; since, if my views are correct, the glacier
exists and is in full life and activity before the secondary blue bands
arise in it, whereas the stratification is a feature of its embryo
condition, already established in the accumulated snow before it begins
its transformation into glacier-ice. In other words, the veined
structure of the glacier is not a primary structural feature of its
whole mass, but the result of various local influences acting upon the
constitution of the ice: the marginal structure resulting from the
resistance of the sides of the valley to the onward movement of the
glacier, the longitudinal structure arising from the pressure caused by
two glaciers uniting in one common bed, the transverse structure being
produced by vertical pressure in consequence of the weight of the mass
itself and the increased rate of motion at the centre.

In the _neve_ fields, where the strata are still horizontal, the few
blue bands observed are perpendicular to the strata of snow, and
therefore also perpendicular to the blue seams of ice and the sheets of
dust alternating with them. Upon the sides of the glacier they are more
or less parallel to the slopes of the valley; along the line of junction
of two glaciers they follow the vertical trend of the axis of the mass;
while at intermediate positions they are more or less oblique. Along the
outcropping edges of the strata, on the surface of the glacier, they
follow more or less the dip of the strata themselves; that is to say,
they are more or less parallel with the dirt-bands. In conclusion, I
would recommend future investigators to examine the glaciers, with
reference to the distribution of the blue bands, after heavy rains and
during foggy days, when the surface is freed from the loose materials
and decomposed fragments of ice resulting from the prolonged action of
the sun.

* * * * *

The most important facts,