James Timmins Chance to Faraday   6 November 1860

Hamstead, Birmingham | 6th Nov: 1860

My dear Sir,

I am much obliged for your note¹. I have directly explained to Lieut. Hyeen that he must not make any communication to others until he has the revised report².

In reference to the term ‘focus’, allow me to suggest the insertion of a definition simply, in a postscript or elsewhere³, if you think it worth while to regard this point at all.

Considering a section of the reflectors made by a plane through the vertical axis of the whole apparatus, the ‘focus’ (as intended in your report) is the common point of intersection, within the apparatus, of the light transmitted from a distant object by the middle of each prism respectively.

Considering the whole apparatus of reflectors, the ‘focus’ becomes a circle (except where it is on the axis) the radius of that circle being the distance ‘aside’.

I am just going to Whitby. On my return I will furnish you with a statement of what has been done, in regard to permanent adjustment[.]

Most truly yours | J.T. Chance

Professor Faraday | &c &c

Endorsed by Faraday: Sent him my figures <(45)>⁴