Faraday to Frederick Arrow   14 March 1864

Royal Institution | 14 March 1864.

My dear Captn. Arrow.

I return you Mr. Chance’s letters -

I do not wish to alter anything I have said in the last paragraph of my last letter to Mr Berthon¹.

The question of optical coincidence of the uprights in respect of the Gibraltar light I leave as we left it when you & Mr Douglas were here[.] Mr. Chance speaks of the loss of light on either side of a lens frame occasioned by the interposition of the lanthorn standard as being about 3 per cent the light being diminished by that amount at about one degree on either side more than in the direct radial line. I do not know how the observation was made;- but the eye is subject to some very curious deceptions in the estimation of the loss of light by or in shadows. I should like to shew you one or two of these in a dark room. I could sufficiently darken my room here if I thought you would not mind taking the trouble to come[.]

Ever My dear Sir | Yours Very truly M. Faraday