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Darwin Correspondence Project

To Robert Hunt   22 July [1855]

Down Farnborough Kent

July 22d

My dear Sir

I thank you most sincerely for your glass-specimens, (which will be of the greatest use to me) & for your very kind letter.1 The latter came quite in time; for I have only finished a few days ago, your very interesting volume (2d. Edit) on Light.—2 The chapter on the relation of light & actinism towards plants is most suggestive,3 & I had determined on trying the 3 viz blue, red & yellow, which you have sent me. But I want extremely to beg one other favour, viz where can I get such glasses.? I have not the least idea where to try?

Do you know with what the Blue & Red (& yellow) (which I think will be the most valuable to me) are coloured; as this, perhaps, would be an aid in getting the right sorts; for I infer from what you say, that the mere colour is not always a safe guide in regard to the power of the glass in intercepting the radiant powers.

After I have been to some glass place, would you permit me to show you any specimens, the manufacturer may have by them? I shall be in London on 7th, 8th & 9th of August, & with your permission will call & show you any glass which I could meet with. If you will send me a line about glass manufacturers you will complete your kindness, for which I am really very much obliged to you.

Pray believe me | My dear Sir | Your’s sincerely | Charles Darwin


R. Hunt 1854, pp. 215–47. These pages are annotated in CD’s copy; on p. 237, CD noted: ‘Make Hybrids under red glass.’


Hunt, Robert. 1854. Researches on light in its chemical relations; embracing a consideration of all the photographic processes. 2d ed. London.


Mentions RH’s book on light [Researches on light in its chemical relations, 2d ed. (1854)]. Asks about coloured glass used in experiments on plants.

Letter details

Letter no.
Charles Robert Darwin
Robert Hunt
Sent from
Source of text
American Philosophical Society (Mss.B.D25.)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 1727,” accessed on 18 February 2020,

Also published in The Correspondence of Charles Darwin, vol. 5