65. Harley St <1>
I am extremely obliged to you for your reference to the description of the Actinometer, <2> the more so that Dr Lindley <3> had previously inquired of several scientific persons without success –
I have thought of a method of measuring the refrangibility of definite rays, which I think cannot fail of possessing sufficient accuracy and facility – If you will make the homogeneous rays I will have the instrument constructed, so as to give it a fair trial –
Yours very truly
H. F. Talbot
C. Wheatstone Esq
20 Conduit St
1. Harley Street, London.
2. Actinometer, an instrument for measuring the intensity of light. The term was coined by Sir John Herschel in ‘Additional Observations on Leslie’s Photometer, &c By William Ritchie, A.M. Rector of the Academy at Tain. In a Letter to Dr Brewster’, Edinburgh Journal of Science,v. 3, 1825, pp. 104–107).
3. Prof John Lindley (1799–1865), botanist.