Faraday to Edward and James Brown   17 December 1847

Royal Institution | 17 Decr. 1847.

Gentlemen

I received your letter of the 30th Ult at Brighton¹: but refrained from answering it until I had had communications from the Trinity house² and had examined your apparatus. You knew by letters from London³ that the fluid had in part escaped from the apparatus & the ignition of the wire had ceased. When I saw the arrangement on the 14th instant I found that all the fluid had leaked out of one cell and that the other four though full were exhausted in their action.

In reference to your proposition, as one affecting the interests of Navigation, and especially a part of it which is under the charge of the Trinity House, I may (as for myself only) say, that I accept the principle as correct; and indeed, as you probably know, the light of a platinum wire ignited by a voltaic battery has been proposed, both in this country & America⁴, for use in coal mines & elsewhere.

As to the use of such an ignited wire in rendering buoys visible at night I am not aware that such a proposition has before been made: but with respect to the proposition itself it is not the principle but the practical application of it which has to be considered. There are many essential requisites without which any proposal for this purpose, however correct its principle, would be of no value. Any arrangement must (to be applicable) bear, not merely the continual lightings of the buoy, but the sudden & violent shocks which it receives when from the action of powerful waves it is brought up suddenly by its moorings; or when a vessel runs against it & it is actually submerged & even for a time capsized. The part shewing the light must be strong enough to bear the blow of ships & boats & yet free & clear enough to shew its light along the surface of the waters. The whole must sustain the vicissitudes of summer & winter; warm & cold. Withall the light must be a certain light & in no respect liable to cease: for an uncertain indication is worse than none. Every part therefore of the apparatus must be sure for the period between each appointed visitation; & at the time of visitation the process of restoration to full activity must be simple and certain[.]

With regard to the apparatus at the Trinity house, I have no doubt you are fully aware, that, it is utterly unfitted in every respect to meet these conditions; and if restored to its best state could not remain half an hour on a buoy without being deranged. It is in fact only competent to demonstrate the principle but does not go one step in the practice. Now it is the latter which, I expect, the Trinity House requires. I do not mean to say that the proposal could not be carried out in practice; but I am sure it would require a very great deal of thought, trial, & perseverance: that many difficulties, some forseen but more unforseen, would arise; and, that after all, it would most probably disappoint the hopes & expectations of the projecter. At all events I believe it is the perfected application which the authorities of the Trinity house would require; for, as a mere principle, it is useless to them.

I do not enter into the points of your letter to me because I think the subject has to be considered on larger grounds i.e. the grounds of perfected practice; but I may just say that I do not expect you could keep an atmosphere of Carbonic acid about the ignited wire: on the other hand I may inform you though perhaps you are aware of the fact that the same battery will heat from 2 to 3 or 4 times as much wire to the same high temperature, when in the form of a moderately close helix, to what can be heated in a horizontal straight line; and also that more wire is heated in a vertical than in a horizontal position[.]

It is perhaps informal of me to write thus direct to you; but it gives me an opportunity of answering your letter and making you aware of my mind. I shall send a copy of this letter to the Secretary of the Trinity house⁵ as the best way of giving my opinion; so, that instead of writing to me, you may, if you have occasion, write to him at once & that will put any further communication into due form[.]

I am Gentlemen | Your Very Obedient Servant | M. Faraday

Messrs. E. & J. Brown | 33 North Road | Preston | Lancashire