George Biddell Airy to Faraday   4 March 1839

Royal Observatory Greenwich 1839 March 4

My dear Sir

I am desirous of complying with your wishes¹, and I am forced to do so with the minimum expenditure of time.

I inclose - 1st A copy of a Report to the Admiralty² (which please to regard as confidential, though it contains no secrets) 2d Copy of an address (oral) to the Liverpool Institution³. If you will read these, you will be well prepared for further instruction. Please to return them to me very safely on Wednesday if you come, or not later, as I am going out on Thursday morning.

The observations of the dipping needles on deck have been reduced: they agree in results with the other observations: and they shew that there is not much permanent vertical magnetic force.

The dipping needles &c on these shewed that the stern end of the ship attracted the marked end of the compass powerfully. The head end had no particular effect.

The Ironside (the second corrected by me at Liverpool) has arrived safely at Pernambuco⁴: her compasses had gone right all the way. - The arrival of this vessel has been announced in the newspapers with the note that her com‑passes were true - but the newspapers forgot to say that her compasses had my corrections - you may set this right if you please⁵.

The discovery that the effect of disturbance is due to the separate causes (permanent magnetism and induced magnetism) has necessitated two correc‑tions which were not required before. 1st The possibility of change in the permanent magnetism renders it necessary that observations should be repeated to discover whether it changes with time: 2d The mathematical circumstance that one term of the effect of induced magnetism cannot be distinguished at one place from permanent magnetism and yet will change at other places, renders it necessary that examination should be made in different localities[.] My con‑clusion from this is, that the magnetic interests of the Iron Navy ought to be put under the care of one person: if you agree with this I wish you would say so⁶.

I shall expect you on Wednesday not later than 1: if you think any thing else can be extracted from me. Probably at all events you would like to see the tables of numbers.

I am dear Sir | Faithfully yours | G.B. Airy

Michael Faraday Esq | &c &c &c