James Drew to Faraday   25 May 1861

Trinity House | May 25

Private

My Dear Mr. Faraday.

In the first place let me thank you for the attention you gave Mr. Ladd on the subject of the Camera - he will [word illegible] I have no doubt give us an instrument convenient & well adapted for the purpose.

I think Mr. Berthon has informed you¹ that the Board have appointed a special Committee to inspect the different Dioptric lights under their management & to report upon any & what attention they may deem necessary - They at the same time made me chairman of the Committee being the Senior member - I hope therefore if I should occasionally trespass somewhat on your time you will treat me as one of your juvenile pupils at the Christmas lecture & condescend to my senile capacity - With your Excellent Focimeter & formula in our hands (dated 19th Octr. & 20th Novr. 1860²) little information I expect will be needed in their application - but will you kindly give me a few other practical hints in answer to the following enquiries.-

1st. To ascertain if the Burner is in centre of the apparatus in addition to intersection of cross lines - could we not with good effect correctly measure any inaccuracy by dropping a plumb bob from the upper rim of the apparatus & exactly measure it on a millimeter measure placed upon the burner[.]

2nd. Would a spirit level with a graduated scale (if such could be made) be of service to find how much the burner or platform might be out of the horizontal –

3. Should the horizon not be visible could you advise any other mode of observation practically within our compass -

4. Professor Airy in his letter in Royal Comm. dated Ap 7/60. (see report p. 77³) speaks of the Prism for the Australian fix’d light as being all “properly curved” & referring to Mr. Gladstones observations on the preceeding [sic] page who speaks of “making the reflecting surface concave”⁴ I am led to ask you whether all our prisms are not ground with flat surfaces -

5th. Could you devise any method to obviate the necessity of the Keepers Keeping Continual watch on the light - Such perhaps as reflecting the light from the lamp to the lower part of the lantern -

I am emboldened to ask you these questions in the knowledge of your usual desire to impart information to those really seeking it[.]

believe me my dear Sir | Yours Very truly | J. Drew