--Believe me ever truly yours,
CHA. LYELL.
* * * * *
SIR C. LYELL TO A.R. WALLACE
_73 Harley Street. July 3, 1867._
My dear Mr. Wallace,--I was very glad, though I take in the _Westminster
Review_, to have a duplicate of your most entertaining and instructive
essay on Mimicry of Colours, etc., which I have been reading with great
delight, and I may say that both copies are in full use here. I think it
is admirably written and most persuasive.--Believe me ever most truly
yours,
CHA. LYELL.
* * * * *
TO HERBERT SPENCER
_Hurstpierpoint, Sussex. October 26, 1867._
My dear Mr. Spencer,--After leaving you yesterday I thought a little
over your objections to the Duke of Argyll's theory of flight on the
ground that it does not apply to insects, and it seems to me that
exactly the same general principles do apply to insects as to birds. I
read over the Duke's book without paying special attention to that part
of it, but as far as I remember, the case of insects offers no
difficulty in the way of applying his principles. If any wing were a
rigid plane surface, it appears to me that there are only two ways in
which it could be made to produce flight. Firstly, on the principle that
the resistance in a fluid, and I believe also in air, increases in a
greater ratio than the velocity (? as the square), the descending stroke
might be more rapid than the ascending one, and the resultant would be
an upward or forward motion.
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