Faraday to Peter Henry Berthon   21 July 1858

Eastbourne | 21. July 1858

My dear Sir

The light which I saw in company with the Deputy Master¹ at the house of the Honble Major Fitzmaurice² had in every respect both as to its high power and the apparatus employed the character of the ordinary oxyhydrogen lime light as used at the Polytechnic & other similar establishments and as I have myself frequently employed it in the Royal Institution. The lime light was proposed many years ago by Lieut. Drummond³ for lighthouse purposes⁴ & I have no doubt was then very fully considered.

The person who superintended the light at Major Fitzmaurice[’s] house, professed to know most about it, & was supposed to be the responsible person, said there were three causes of its superiority over the known lime light[.] One of these was in something added to the oxygen & hydrogen gases this was kept secret - Another was in the nature of the medium which as far as I could then judge was lime but this also was kept secret. The oxygen & hydrogen gases were preserved in a compressed state in strong iron cylinders and the third cause of superiority was assumed to exist in the friction of the gases at the valves as they issued from the cylinders; this friction being supposed to produce an electric or some other favourable state.

<⁵> Speaking for myself I should as a practical philosophic adviser first require to know all the circumstances and liabilities of the light in order to judge of their permissibility & probable utility. I should therefore require to know the two secret points; & I should desire this the more earnestly because I place no confidence in the third supposed cause of advantage.

<⁶> Besides these secrets I should then require to know in what form or arrangement the light is to be applied practically - whether as a central light or in the manner of lamps, i.e. each medium being in its own reflector also whether when in reflectors as a central light a fixed light, or a revolving light for each of these would require different consideration as to arrangement, expence, power of the light, & its proper service. In any case the assumed advantage of the mode of application should be stated - If that advantage be in superior illumination; then I should desire to know the cost of the light and the proof that the estimation was correct and should also require experiments by which the light could be measured in relation to an Argand or Fresnel lamp; & the cost of the preparation and consumption of the gases be ascertained[.]

<⁷> Next would come trials respecting the time during which such a light might be left - whether, as under present arrangements, the time might extend to an hour or more without fear - or whether the attention must be constant:- for very much of the safety & certainty of a light depends upon its comparative steadiness when arranged & left to itself.

<⁸> Then must be considered the preparation of the two gases Oxygen & hydrogen & the peculiar substance to be added to them;- the quantity of the gases required for a winters night; the storing of the gases;- and as compression is supposed to be necessary, the engine pump apparatus required for that compression. Also the peculiar knowledge & care both chemical & engineering required in the persons taking charge of these points.

<⁹> As the gases are very explosive when mixed, and as the Trinity house have in the prevention of plans proposed to them had an explosion in a lighthouse, so the possibility of such an event under any circumstances must be most carefully considered & for that reason the details regarding the preparation & use of the oxygen & hydrogen must be fully stated.

<(6)> Such is the general order in which I should have to consider the subject & I think it the only manner in which it can be usefully developed. It is not until that has been done that I think trial in a light house would be of service. When tried in a light house it should be in some form available in practise. I do not know that a single fixed narrow concentrated ray is ever required. If tried as a revolving light it will of course give a very intense flash; but its divergence, & therefore its time, will be small compared to the Argand lamps in reflectors perhaps only one third.

If it be tried as a fixed light merely for the purpose of a visible effect, then in order to make it instructive for lighthouse purposes, it ought to be compared with the usual oxyhydrogen lime light, or Drummond light; and if possible with the Magnetic Electric light: these also being each in its own reflector.

Perhaps I have gone more into this matter than you required of me but I do not see any other way in which a useful practical result may be obtained & disappointment avoided¹⁰.

I am | My dear Sir | Very Truly Yours | M. Faraday

P.H. Berthon Esqr | &c &c &c