From G. G. Stokes 27 February 1868
The Royal Society, | Burlington House, London. W.
27th Feb. 1868
My dear Sir,
I told your son I fancied from a very hasty examination made a long time ago that the play of colours in the Peacock’s tail was a phenomenon of diffraction.1 I fancied I recollected having seen very fine fibres or ciliæ which might account for it. But a more careful examination under the microscope leaves little doubt in my mind that it is the quasi-metallic reflexion exhibited by certain colouring matters having very intense power of absorption. Murexide and platinocyanide of Magnesium2 are good examples, or to take substances more easily procured carthamine,3 which is sold in the form of the so-called pink saucers, and several of the analine colours, rosanaline for instance.4 If you pour 2 or 3 drops of a solution, tolerably pure, of these colouring matters on glass and allow it to evaporate, a film is left which is one colour by transmitted light and another by reflected light, and the reflected colour has that metallic aspect seen in the peacock’s tail. The leaflets, if I may so call them, of the feather (I describe the feather as a bipinnate leaf and speak of the 2ndary leaflets i.e. the leaflets of the primary divisions) of the peacocks tail feathers, in those places where the feather shows that beautiful metallic green, are red by transmitted light.
I mean to make some further experiments on the subject.
You will find a paper of mine on the optical phenomenon in the Phil. Mag. for Dec. 1853 (Vol 6 p 393 of Series 4).5 I do not mention any feathers in the paper.
I am dear Sir | Yours very truly | G. G. Stokes
Chas. Darwin Esq
Footnotes
Bibliography
Nieto-Galan, Agustí. 2001. Colouring textiles: a history of natural dyestuffs in industrial Europe. Boston Studies in the Philosophy of Science vol. 217. Dordrecht; London: Kluwer Academic Publishers.
Stokes, George Gabriel. 1853. On the metallic reflexion exhibited by certain non-metallic substances. Philosophical Magazine 4th ser. 6: 393–403.
Summary
On the play of colours in the peacock’s tail.
Letter details
- Letter no.
- DCP-LETT-5943
- From
- George Gabriel Stokes, 1st baronet
- To
- Charles Robert Darwin
- Sent from
- Royal Society
- Source of text
- DAR 84.1: 47–50
- Physical description
- ALS 7pp
Please cite as
Darwin Correspondence Project, “Letter no. 5943,” accessed on 18 April 2024, https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-5943.xml
Also published in The Correspondence of Charles Darwin, vol. 16