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of the particles, I applied this method of research to slaty 
rocks, by preparing sections of such extreme thinness as to 
admit of being examined with very high powers, and have 
been thus led to form a theory materially different from any 
yet propounded, which will, I think, not only explain the 
structure, but every fact I have yet met with. As already 
mentioned, the organic remains found in these rocks have 
been observed to be so changed in their form as to indicate 
a compression of the rock in a line perpendicular to the 
plane of cleavage, and an elongation in the line of dip. 
What I have seen enables me to confirm this fact; and I 
have also myself observed several others, most clearly proving 
that this change of dimensions has occurred. 
Vertical Section seen in the Cliffs near Ilfracombe, North Devon. 
Scale, 1 Inch to 1 Foot. 
Fine-grained, dark coloured, shaly 
slate ; the bedding shewn by bands 
of coarser grain and lighter colour, 
which, in the upper part, are not 
contorted. The cleavage is well de- 
veloped, and dips about 60° to S. by 
E. 
Much contorted bed of coarser- 
grained light-coloured sandy slate, 
wish less perfect cleavage. 
Fine-grained slate, as at the upper 
part. 
