260 
INTERNAL STRUCTURE AND 
dered the strata nearly vertical, these blue bands 
follow their trend so closely that it is almost im- 
possible to distinguish one from the other. It 
will be seen, on referring to the wood-cut on page 
258, where the close, uniform, vertical lines rep- 
resent the true veined structure, that at several 
points of that section the lines of stratification 
run so nearly parallel with them, that, were the 
former not drawn more strongly, they could not 
be easily distinguished from the latter. Along the 
margins, also, in consequence of the retarded mo- 
tion, the blue bands and the lines of stratification 
run nearly parallel with each other, both follow- 
ing the sides of the trough in which they move. 
Undoubtedly, in both these instances, we have 
two kinds of blue bands, namely : those formed 
primitively in a horizontal position, indicating 
seams of stratification, and those which have 
arisen subsequently in connection with the move- 
ment of the whole mass, which I have occasion- 
ally called bands of infiltration, as they appeared 
to mo to be formed by the infiltration and freez- 
ing of water. The fact that these blue bands are 
most numerous where two glaciers are crowded 
together into a common bed naturally suggests 
pressuro as their cause. And since the beautiful 
experiments of Dr. Tyndall have illustrated the 
internal liquefaction of ice by pressure, it be- 
comes highly probable that his theory of the ori- 
