Faraday to Peter Henry Berthon   7 July 1864

Royal Institution | 7th July 1864

Sir

I have carefully examined the First Class Lighting Apparatus constructed by M. Sautter, to which your letter of the first of this month¹ refers, and found it in every respect satisfactory. The glass is good in colour; is good in respect of striae;- is good as to bubbles; and is well worked. It also appears to be well put together in the frames & the pieces have been well adjusted so as to act together as one good whole. The adjustments & constructions according to the specifications have been well attended to. The lamp (of four wicks) is on the hydraulic principle and constructed under Captn. Nisbits directions. The flame was good white & steady:- had an average height of three inches of solid flame independent of the forking above.

There are two accidental flaws resulting from fracture but they are not large, nor on the more important or dioptric parts of the apparatus; but on two of the reflecting prisms. The excellency of the work as a whole justifies me in passing them².

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

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