Faraday to Peter Henry Berthon   11 October 1862

Royal Institution | 11 October 1862

Sir

According to your instructions I have been to Mr Chances works (with Captn Were) and examined carefully the Hanois light in relation to its optical parts & adjustment & generally in other respects[.] It is a revolving holophotal light having 16 sides – more particularly described in the specification which I transmit to you herewith – It is a very fine apparatus and having carefully examined it both by day & by night as respects the quality of the glass the grinding – the construction & the adjustment I am prepared to give it unqualified approbation[.] There are as many as 672 separate pieces of glass but the adjustment of all is perfect according to the foci given; & those pieces that have to act together in one panel act as one piece of glass. I do not see that I can say any thing more in reply to your instructions¹[.]

I am Sir | Your Very Obedient humble Servant | M. Faraday²

P.H. Berthon Esq | &c &c &c