Faraday to Peter Henry Berthon   20 November 1863

Royal Institution | 20 Novr. 1863

Sir

In regard to your letter of the 18th instant¹ accompanying one from Mr. Douglas² relating to the Godrevy light cooking range and also some deposited crust from the upper part of the copper smoke pipe & wind guard, I have to state that the crust is a mixture of sooty matter and a cupreous salt - namely sulphate of copper resulting from the corrosive action of the smoke upon the metal consequent upon the sulphur that is in the fuel. It is the sulphurous gas produced by the fuel which has caused the corrosion and the reason why the action is almost entirely confined to the wind guard & upper part of the tube is that these parts being free from the fire & exposed to the cold air are at so low a temperature as to allow of the condensation of part of the water formed by combustion without which the corrosion of the copper would go on only very slowly. The sea spray has little or nothing to do with the decay - There is no trace of sea salt or sea-water action either in the crust or on the corroded copper & the action itself is according to Mr. Douglas report limited to the interior of the smoke passages³.

I am Sir | Your Obedient humble Servant | M. Faraday

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