lt. I cannot find that you
say anywhere what is the depth of the sea between the Straits of Lombok,
but you mention that it exceeds 100 fathoms. I am quite willing to infer
that there is a connection between these soundings and the line of
demarcation between the two zoological provinces, but must we suppose
land communication for all birds of short flight? Must we unite South
America with the Galapagos Islands? Can you refer me to any papers by
yourself which might enlighten me and perhaps answer some of these
queries? I should have thought that the intercourse even of savage
tribes for tens of thousands of years between neighbouring islands would
have helped to convey in canoes many animals and plants from one
province to another so as to help to confound them. Your hypothesis of
the gradual advance of two widely separated continents towards each
other seems to be the best that can be offered. You say that a rise of
a hundred fathoms would unite the Philippine Islands and Bali to the
Indian region. Is there, then, a depth of 600 feet in that narrow strait
of Bali, which seems in my map only two miles or so in breadth?

I have [been] confined to the house for a week by a cold or I should
have tried to see you. I am afraid to go out to-day.--Believe me ever
most truly yours,

CHA. LYELL.

* * * * *

SIR C. LYELL TO A.R. WALLACE

_73 Harley Street. April 4, 1867._

My dear Mr. Wallace,--I have been reading over again your paper
published in 1855 in the _Annals_ on "The Law which has regulated the
Introduction of New Species"; passages of which I intend to quote, not
in reference to your priority of publication, but simply because there
are some points laid down more clearly than I can find in the work of
Darwin itself, in regard to the bearing of the geological and zoological
evidence on geographical distribution and the origin of species. I have
been looking into Darwin's historical sketch thinking to find some
allusion to your essay at page xx., 4th ed., when he gets to 1855, but I
can find no allusion to it. Yet surely I remember somewhere a passage in
which Darwin says in print that you had told him that in 1855 you meant
by such expressions as "species being created on the type of
pre-existing ones closely allied," and by what you say of modified
prototypes, and by the passage in which you ask "what rudimentary organs
mean if each species has been created independently," etc.,