Faraday to Peter Henry Berthon   14 January 1864

Royal Institution | 14 January 1864.

Sir

Mr. Dicksons specification¹ relates to Improvements in Voltaic apparatus & the production of voltaic Electricity. His claims in it are for the application of heat generally & for the arrangement of the parts of the apparatus described. No mention is made in it of the production of the Electric light or of any lamp or regulator to be used for that purpose. In his letter² Mr. Dickson say[s] that the cost of the Voltaic apparatus with its necessary steam boiler would be from £50 to £100 and that the daily cost for materials necessary to give a very brilliant light would be about 10 to 20 shillings[.]

Heated cheap materials form the base on which the construction of the Voltaic apparatus is founded. The Positive poles are to be Iron, Zinc, Tin, lead, copper carbon &c. The Negative poles are to be Carbon Platinum copper &c. The positive electrolytes or fluids are to be solutions of the alkaline & earthy sulphurets; - of the alkalies or alkaline earths:- and the Negative liquids are to be oil of vitriol or other acids, strong, or more or less diluted, and also pure or saturated by the introduction of various gases. These are to be adjusted in cells of different kinds some metallic, some of porous earthen ware and are then to be heated by a furnace, or a gas jet, or in water or steam jackets.

The use of these materials & means might lead to a great variety of voltaic batteries; yet no one has been selected or described as that tried, proved, chosen, & recommended, and upon which therefore I might fix my attention. But it seems to me that any such battery would require a complicated case above the ordinary voltaic batteries[.] A temperature of 360°F or even higher has to be used & maintained at times with strong oil of vitriol; & at other times, other & lower temperatures down to & below boiling water. Hot strong oil of vitriol has to be maintained in contact with tender porous earthen ware cells, the charging & discharging of these cells has to be attended to, and though no particular battery has as yet been selected either by judgment or experiment, I am persuaded that the case needful for any one constructed by the specification, would be greater than for an ordinary battery, or for such an one as that proposed by Dr. Watson³ & already tried by the Trinity House.

It seems to me that Mr. Dickson should first work his Patent & evolve a battery for ordinary electric uses; and that when such a battery has been employed for a sufficient length of time and has justified itself in workshops, in comparison with the batteries of Grove, Daniell, Watson, & other persons; that then the time will come when it may be considered in reference to lighting purposes & the service of a lighthouse. In regard to the latter use, I have only to say that it will have to meet the observations & objections that were made long ago to Dr. Watsons battery (Report 15 Aug 1854⁴) when under investigation by the Trinity House⁵[.]

I am Sir | Your Very faithful Servant | M. Faraday

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