eless
in me troubling you with my old speculations.

LETTER 494. TO A.R. WALLACE. March 22nd [1869].

(494/1. The following extract from a letter to Mr. Wallace refers to his
"Malay Archipelago," 1869.)

I have only one criticism of a general nature, and I am not sure that
other geologists would agree with me. You repeatedly speak as if the
pouring out of lava, etc., from volcanoes actually caused the subsidence
of an adjoining area. I quite agree that areas undergoing opposite
movements are somehow connected; but volcanic outbursts must, I think,
be looked at as mere accidents in the swelling up of a great dome or
surface of plutonic rocks, and there seems no more reason to conclude
that such swelling or elevation in mass is the cause of the subsidence,
than that the subsidence is the cause of the elevation, which latter
view is indeed held by some geologists. I have regretted to find so
little about the habits of the many animals which you have seen.

LETTER 495. TO C. LYELL. Down, May 20th, 1869.

I have been much pleased to hear that you have been looking at my
S. American book (495/1. "Geological Observations on South America,"
London, 1846.), which I thought was as completely dead and gone as any
pre-Cambrian fossil. You are right in supposing that my memory about
American geology has grown very hazy. I remember, however, a paper on
the Cordillera by D. Forbes (495/2. "Geology of Bolivia and South Peru,"
by Forbes, "Quart. Journ. Geol. Soc." Volume XVII., pages 7-62, 1861.
Forbes admits that there is "the fullest evidence of elevation of the
Chile coast since the arrival of the Spaniards. North of Arica, if we
accept the evidence of M. d'Orbigny and others, the proof of elevation
is much more decided; and consequently it may be possible that here,
as is the case about Lima, according to Darwin, the elevation may have
taken place irregularly in places..." (loc. cit., page 11).), with
splendid sections, which I saw in MS., but whether "referred" to me or
lent to me I cannot remember. This would be well worth your looking to,
as I think he both supports and criticises my views. In Ormerod's
Index to the Journal (495/3. "Classified Index to the Transactions,
Proceedings and Quarterly Journal of the Geological Society."), which I
do not possess, you would, no doubt, find a reference; but I think the
sections would be worth borrowing from Forbes. Domeyko (495/4. Reference
is made by Forbes in his paper on Boliv