Faraday to Peter Henry Berthon   16 October 1862

Royal Institution | 16 Octr. 1862

Sir

In relation to the Red light that is to be used at the Hanois lighthouse¹ I am of opinion that it should be produced by a red lamp glass. Such a glass was shown to us in the lamp at the recent examination at Birmingham. These glasses are made I believe only by one house at Birmingham - the house of Lloyd & Summerfield² I think; but as Mr Chance gave the address to Captn Were I did not particularly note it. It is the house which makes red glasses for all the Northern lights. The colouring matter for red glasses ought to be either copper or gold. I believe that used by the house referred to above is copper.

I am Sir | Your Very Obedient humble Servant | M. Faraday

P.H. Berthon Esqr | &c &c &c