Edward and James Brown to Faraday   30 November 1847

Preston Nov 30 / 47

Dear Sir

We have for some time been in London, demonstrating to the Corporation of Trinity House a method for illuminating Buoys, and as they have concluded to place the subject into your hands, to report upon it, we now address you, in order to explain to you, the nature of our method, thinking, that it may facilitate your enquiry.

The principle upon which the light is made, is by passing through some fine Platina wire, a current of electricity, generated by a constant or sustaining Battery of 5 cells each 13 inches deep, by 6 inches square, of wood. The copper & zinc cylinders are separated by porous diaphra[g]ms of brown paper.

We had intended to have the diaphra[g]ms made of porous hose, but the maker so frequently disappointed us, that we were compelled to substitute paper in their stead, & consequently were obliged to make them in the cylindrical form.

Into each cylinder of copper, there is a saturated solution of sulphate of copper, & about a pound suspended in crystals in each cylinder, so as to keep up the action for a few weeks; & outside of the copper in contact with the zinc is a solution of common salt.

The Platinum wire is enclosed in an air tight cylinder filled with carbonic acid gas, as its brilliancy is thereby much increased.

As by being exposed to the cold (sometimes very intense on a Buoy) the glass cylinder as in the present arrangement would be liable to fracture, we found that by enclosing it in a double glass the liability to fracture is removed. In the the [sic] apparatus at present in Trinity House the double Glass is not used, neither have we covered the copper diaphra[g]ms as it would be necessary upon a Buoy with membrane or any suitable substance.

Trusting you will give the subject as little publicity as you can & will be ready to answer any questions connected with the subject,

We remain Dear Sir | Your humble servants | E & J. Brown

P.S. Our address. | E. & J. Brown | 33 North Road | Preston | Lancashire

To M. Faraday Esq D.C.L

Address: For | M. Faraday Esq D.C.L. &c | Royal Institution | Albemarle Street | London