Peter Henry Berthon to Faraday   10 July 1857

Trinity House, London, E.C.- | 10th July, 1857.

Sir,

Referring to previous correspondence on the subject of the Catadioptric Lighting Apparatus intended for use at the Bishop Rock Light House, I am directed by the Elder Brethren to state that, being desirous that the Light to be exhibited from that Light House should be of the most powerful description, and having been informed that the Apparatus in question, although purchased in the Year 1850, combines all the advantages of recent improvements, and having reason to believe that the Experiment to which the two Sections of it which are fitted up at Blackwall, were subjected on the Evening of the 31st March last¹, did not afford a just Estimate of it’s power, in consequence of the shortness of the distance from which it was observed, the Elder Brethren are desirous of obtaining your further opinion on the subject.

It has been suggested that a holophotal Apparatus of 12 Sections to the Circle may be found practically more effective than that in question which contains 24 Sections, I am therefore to request you will favor the Elder Brethren with your opinion as to which of the three you consider may with the best effect, having regard to the Elevation, Position, and intended purposes of the Bishop Rock Light, be used in the exhibition of the Light thereat, viz.

The Apparatus already procured, A holophotal Apparatus of 12 Sections, or a Catoptric Apparatus, with the reflectors arranged in the same manner as the three which were observed at Blackwall on the Evening above alluded to.-

I am, | Sir, | Your most humble Servant | P.H. Berthon

M. Faraday Esq., | &c. &c. &c. | Royal Institution, | Albemarle Street.