Peter Henry Berthon to Faraday   19 February 1857

Trinity House London | 19 February 1857

My dear Sir,

I have been called upon by the Board of Trade for the Results of any Experiments which may from time to time have been made of the relative powers of the Fresnel System of Lights as compared with the Argand Lamps & Reflectors, I do not find it recorded that we have ever had any general reports from you on the Subject, but still such may have been made and not purposely recorded, may I therefore trespass upon you with a request that you will inform me whether your attention has ever been directed specially to the comparative powers of the two systems? and if so whether you have ever reported thereon & when?

I find that amongst the Brethren a general Opinion prevails that when seen in the exact focus the Reflector is as powerful as the lens if not more so but that the latter has the advantage of more general diffusion of Light.- and is consequently the best for fixd Lights, & the former for revolving,-

Believe me | My dear Sir | Yours very faithfully | P.H. Berthon

M. Faraday Esq | &c &c &c

Endorsed by Faraday: Replied with the accompanying list of references¹