George Gabriel Stokes to Faraday   13 November 1855

69 Albert Street Regent’s Park | London Nov 13, 1855

My dear Sir,

As I was walking into town after I had posted your letter¹ I thought I recollected having made an error through inadventure. The tangent of the ½ vertical angle of the cone is <square root>⅔. I wrote down the logs of 2 and 3 from memory and subtracted but forgot to divide by 2. The true angle is 39˚14’ giving for the whole angle of the cone 78˚28’. This emendation as far as it goes favours the explanation which I gave of the cause of the setting of the phosphorus in your experiment.

As I don’t know whether simply Brighton will find you I direct to the Royal Institution.

Yours very truly | G.G. Stokes

Profr. Faraday