ave no bearing.

My new edition of the "Origin" (510/4. Fifth edition, May, 1869.) will
be published, I suppose, in about two months, and for the chance of your
liking to have a copy I will send one.

P.S.--I wish that you would turn your astronomical knowledge to the
consideration whether the form of the globe does not become periodically
slightly changed, so as to account for the many repeated ups and downs
of the surface in all parts of the world. I have always thought that
some cosmical cause would some day be discovered.

LETTER 511. TO C. LYELL. Down, July 12th [1872].

I have been glad to see the enclosed and return it. It seems to me
very cool in Agassiz to doubt the recent upheaval of Patagonia, without
having visited any part; and he entirely misrepresents me in saying that
I infer upheaval from the form of the land, as I trusted entirely to
shells embedded and on the surface. It is simply monstrous to suppose
that the terraces stretching on a dead level for leagues along the
coast, and miles in breadth, and covered with beds of stratified gravel,
10 to 30 feet in thickness, are due to subaerial denudation.

As for the pond of salt-water twice or thrice the density of sea-water,
and nearly dry, containing sea-shells in the same relative proportions
as on the adjoining coast, it almost passes my belief. Could there have
been a lively midshipman on board, who in the morning stocked the pool
from the adjoining coast?

As for glaciation, I will not venture to express any opinion, for when
in S. America I knew nothing about glaciers, and perhaps attributed much
to icebergs which ought to be attributed to glaciers. On the other hand,
Agassiz seems to me mad about glaciers, and apparently never thinks of
drift ice.

I did see one clear case of former great extension of a glacier in T.
del Fuego.

LETTER 512. TO J. GEIKIE.

(512/1. The following letter was in reply to a request from Prof. James
Geikie for permission to publish Mr. Darwin's views, communicated in a
previous letter (November 1876), on the vertical position of stones in
gravelly drift near Southampton. Prof. Geikie wrote (July 15th, 1880):
"You may remember that you attributed the peculiar position of those
stones to differential movements in the drift itself arising from the
slow melting of beds of frozen snow interstratified into the gravels...I
have found this explanation of great service even in Scotland, and
from what I have seen of t