12 May 1828
My dear Sir
It happens by a singular fatality that while I am in hopes of obtaining from you a valuable fragment of literature, I should have to apply to you for a no less valuable fragment of profound science
Mr. Herschel <1> informs me that you are in possession of a demonstration of the remarkable theorem by which the late Mr. Fraunhofer <2> deduced the discontinuous colours of his spectra from the laws of interference: and as I am too lazy, or perhaps too busy, or too ignorant to attempt to make it out for myself, I should be much obliged if you would favour me with a sight of it: concluding, as I do from Herschel’s expression, that it has not been published –
Believe me Dear sir very sincerely yours
W. H. Fox Talbot Esq
31 Sackville Street
1. Sir John Frederick William Herschel (1792–1871), astronomer & scientist.
2. Joseph von Fraunhofer (1787–1826), optician, Munich.