262 
INTERNAL STRUCTURE AND 
ward progress of the glacier and the pressure to 
which it is subjected. The secondary blue bands 
intersect the planes of stratification at every pos- 
sible 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 strat- 
ification. 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 second- 
ary blue bands arise in it, whereas the stratifi- 
cation is a feature of its embryo condition, al- 
ready 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 mar- 
ginal 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 be- 
ing produced by vertical pressure, in consequence 
of the weight of the mass itself and the increased 
rate of motion at the centre. 
In the nev£ fields, where the strata are still 
