Frederick Madan to Faraday   1 September 1842

Trinity House | Septr 1st 1842

My dear Sir

I find on looking again, I was altogether wrong about the dip of the horizon. I took it out of "Norie's¹ Navigation", where it is not given beyond 100 feet², & without thinking I stupidly multiplied that by 5 1/2, forgetting that it decreases as the altitude increases. In "Kerigan's³ Navigation" it is calculated to 500 feet, & for that altitude it gives 21'.24", & about 22' 1/2 for 550⁴, which agrees nearly with your calculation. They are both practical navigation Books, & no doubt they are to be found at the R.I. but if not I should be happy to shew them to you here any day. Tuesday is always best, as it is our Board day.

Still however I should say, & I think you appear to agree with me that some depression of the light would be desirable. Those I have spoken to here, including Captn Drew & Fitzroy⁵, coincide with me in opinion that it should be 1˚ degree that the strongest ray may shew about 20 miles distant & that there may be good light near the Island.

I have been uncertain how the subject had better be brought before the Deputy Master⁶, on his return next week: whether it would not come with most weight from you, for I fear he would scarcely attend to it from me, & there is no time to be lost, as Mr. Wilkins goes down on Monday⁷ to fix it. Capt Drew however having returned yesterday, & being much interested about the light, as it has been altered principally at his suggestion, I have put the matter into his hands, & he promises to urge it on the Deputy Master on Tuesday next⁸.

Do you not think it would be more satisfactory to alter the Lenses slightly? that it may be quite perfect. Mr. Wilkins seemed to say he could easily do it, & I suppose 1/8th out at the top & as much in at the bottom would be the utmost that could be required.

I have so little faith in Mr. Wilkins, that I should much like you to visit the Light after he has fixed it, & overhaul the apparatus thoroughly, & I should be happy to accompany you. By having our Steamboat to meet us at Bristol, it could not exceed a week's work at the utmost.

in haste Your's sincerely | Fredk Madan