Robert Were Fox to Faraday   13 September 1838

Falmouth 13 / 9mo 1838

Dear Friend,

At our last meeting of the Cornwall Polytechnic Society held more than eleven months ago, I exhibited specimens of clay which had become laminated by long continued voltaic action, & others in which veins of oxide of copper &c had been formed by the same agency¹; the veins & insulated portions of the oxide having been deposited in the middle of the clay, which had been pre‑viously moistened w[it]h a solution of sulphate of copper². Since then I have obtained veins of oxide of iron, carbonate of Zinc &c, extremely well defined, and I sent a specimen of the latter to Newcastle³.

In my first experiments the voltaic action was continued for several months, but from subsequent ones which a friend⁴ of mine & I have made, it seems that similar results may be had in a week or two, or less time, by means of Daniells sustaining battery⁵, consisting of four or more pair of plates or rather cylinders.

The clay may be placed between horizontal or perpendicular plates of metal, (copper & zinc, for instance.) In the former case, horizontal veins are formed, & in the latter vertical ones. In fact, the veins, as well as the laminae, are always perpendicular to the voltaic currents, & generally very decided cracks or fissures, produced apparently by the same agency, have made their appearance in the clay even when quite hot.

These facts have a decided bearing on very important geological phenomena & it would appear from them that the directions of the laminae of the schistose & other rocks, ought to indicate those of the electricity.

I have to return thee many thanks for two of thy valued & highly interesting papers recd some time ago⁶.

I remain thine very truly | R.W. Fox

Address: Michael Faraday Esq | &c &c &c | Royal Institution | Albemarle St | London