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Darwin Correspondence Project


To John Tyndall   8 September 1870

Down. | Beckenham | Kent. S.E.

Sep 8th. 1870

My dear Tyndall

Your whole discourse strikes me as grand & most interesting.1 What you say about Pangenesis is quite correct, & your expression, “not only is the organism as a whole wrapt up” &c is most happy.2 What you say about me, coming as it does from you, has pleased me extremely, so much that there must be clouds of vanity in my mind to bring out such pleasant sensations as your remarks passed through them— you are a rash man to say a word for Pangenesis, for it has hardly a friend amongst naturalists, yet after long pondering (how true your remarks are on pondering) I feel a deep conviction that Pangenesis will some day be generally accepted. I have been particularly delighted by your “as if” argument. These words have lately been fired at me, & if I had been forced to answer, I should not have known what to say, now I cd answer by a round of your artillery.3 I have ventured to mark (p. 12. & 40) two sentences which seem to me not so perfectly lucid as all the rest. I may also mention that in the discussion on “the particles of our sky” I read 2 or 3 pages thinking that you referred to the atoms of the air: wd it not be well for blunderers to shew in the early part, that you refer to foreign particles?4

With hearty admiration & thanks, yours very truly | Ch. Darwin

P.S. I return the proofs by this post.

When in Brazil I was much struck with the frequent blue haze & I quote (p. 32 of my travels) Humboldt’s remark on “the thin vapour which, without changing the transparency of the air, renders its tints more harmonious & softens its effects”.5

It seemed to me that this phenomenon was much more strongly marked in the tropics than in our temperate regions—

On one day when the beautiful pale blue haze had come on very strong, the difference between the dew point & temperature by Daniel’s hygrometer6 had increased from 7o.5. to 17o


CD refers to Tyndall 1870. See letter from John Tyndall, 7 September 1870.
CD’s hypothesis of pangenesis was presented in Variation 2: 357–404. Describing pangenesis, Tyndall had written: ‘Not only is the organism as a whole wrapped up in the germ, but every organ of the organism has there its special seed’ (Tyndall 1870, p. 32).
Tyndall used the expression ‘as if’ to describe the basis on which certain theoretical conceptions were believed. Thus the phenomena of light occur as if the medium of the ether existed. He argued that many assumptions of everyday life were based on the same ‘as if’ principle (Tyndall 1870, p. 10). For Tyndall’s discussion of pondering in relation to scientific discovery, see Tyndall 1867, p. 655, and Correspondence vol. 15, letter to J. D. Hooker, 2 September [1867] and n. 5.
The phrase ‘particles of our sky’ appears in Tyndall 1870, p. 26.
The quotation from Alexander von Humboldt appears on page 32 of Journal of researches 2d ed.
CD refers to the dew-point hygrometer designed by John Frederic Daniell (ODNB).


CD finds JT’s discourse "grand and most interesting" [On the scientific use of the imagination (1870)]. Flattered by what JT says about him.

He is "a rash man to say a good word for Pangenesis for it has hardly a friend among naturalists".

CD is much struck with what JT says about "pondering" and delighted by his "as if" argument.

Please cite as

Darwin Correspondence Project, “Letter no. 7319,” accessed on 22 October 2016,