Faraday to Peter Henry Berthon   27 April 1864

Royal Institution | 27 April 1864.

Sir

I have according to your instructions¹ examined the two lighting apparatus intended for the River Gambia (now standing in the workshops of Mr. Wilkins) both by day & by night and have to report well upon them. They consist of two fourth order apparatus like each to each but they are improved in power by two additional reflecting prisms one above & one below and their horizontal range is 240° in three lengths or pannels of 80° each[.]

The glass is excellent in character both in respect of colour bubbles & striae:- the workmanship & adjustments also are good the light image entered regularly into different parts of the glass under examinations extending to distances of 70 feet. The metal & lamp work appeared to me to be excellent. The solid flame was about or above 2 inches high[.]

I have no criticism to make; but approve of the apparatus[.]

I am Sir | Your Very faithful | obedient Servant | M. Faraday

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