Faraday to Peter Henry Berthon   11 November 1857

Royal Institution | 11 Novr. 1857

Sir

The errors of arrangement referred to in my letter of the 24th Ultm¹ have been corrected. I examined the lighthouse at the Trinity Wharf on Monday² & yesterday Evening the Deputy Master³ & Elder brethren again proceeded to observe the results from Hornchurch. The night was very good; dark but far clearer than before so that all the lights were well seen. According to my own impression, the 7 reflectors in one face had the pre-eminence[.] That light differed from the great lens in having a more disc like character & longer duration for the same velocity of revolution. The great lens was more star light but inferior in power[.] The Buchaness or three reflectors in face had I think the due or expected relation to the seven reflectors, possessing as well as I could judge nearly one half of their power[.] The Bishops light lenses rose considerably in value by the adjustment of the lamp - They now surpassed the Buchaness in power though their duration was not so long for the same velocity of revolution. They recur much quicker indeed as three to once⁴[.]

I have the honor to be | sir | Your Very Obedient faithful Servant | M. Faraday

H.P. [sic] Berthon Esqr | &c &c &c