direction of dip than in any case which I have met with; the Rogers
doctrine of the ridge being thrown up by great waves I believe is
monstrous; but the manner in which the ridges have been thrown over (as if
by a lateral force acting on one side on a higher level than on the other)
is very curious, and he now states that the cleavage is parallel to the
axis-planes of these thrown-over ridges. Your case of the limestone beds
to my mind is the greatest difficulty on any mechanical doctrine; though I
did not expect ever to find actual displacement, as seems to be proved by
your shell evidence. I am extremely glad you have taken up this most
interesting subject in such a philosophical spirit; I have no doubt you
will do much in it; Sedgwick let a fine opportunity slip away. I hope you
will get out another section like that in your letter; these are the real
things wanted.


LETTER 538. TO D. SHARPE.
Down, [January 1847].

I am very much obliged for the MS., which I return. I do not quite
understand from your note whether you have struck out all on this point in
your paper: I much hope not; if you have, allow me to urge on you to
append a note, briefly stating the facts, and that you omitted them in your
paper from the observations not being finished.

I am strongly tempted to suspect that the cleavage planes will be proved by
you to have slided a little over each other, and to have been planes of
incipient tearing, to use Forbes' expression in ice; it will in that case
be beautifully analogical with my laminated lavas, and these in composition
are intimately connected with the metamorphic schists.