[160] This was remarkably the case at Huel Sparnon, near Redruth, where the cobalt was discovered between two portions of a dislocated lode; and the same was observed by Mr. Percival Johnson in a small mine worked for nickel, near St. Austell.
[161] On the process used for obtaining artificial veins in clay: by T. B. Jordan; Sixth Annual Report of the Royal Cornwall Polytechnic Society. See also my memoir, already referred to, in the Memoirs of the Geological Survey and Museum of Practical Geology, vol. i.
[162] See Becquerel, Traité Experimental de l’Electricité, &c. Electrical Experiments on the formation of Artificial Crystals: by Andrew Crosse, Esq.; British Association Reports, vol. v., 1836. The lamination of clay and other substances is described in my memoir referred to, Note p. 226.
[163] Report on the Geology of Cornwall, Devon, and West Somerset, by Sir Henry T. De la Beche: Theoretical observations on the formation and filling of Mineral Veins and Common Faults, p. 349.
[164] The following analyses of waters from deep mines were made by me in 1840, and, with many others, published in the Reports of the Royal Cornwall Polytechnic Society.
| Consolidated Mines, Gwennap, Cornwall. | In 1,000 grains of water. |
|---|---|
| Muriate of soda | 1·5 |
| Sulphate of lime | ·5 |
| Sulphate of iron | ·15 |
| Sulphate of copper | 1·25 |
| Silica | ·15 |
| Alumina | ·3 |
| —— | |
| Total | 3·7 |
| United Mines, Gwennap. | |
| Muriate of soda | 1·10 |
| Muriate of lime | ·15 |
| Sulphate of soda | ·50 |
| Sulphate of lime | 1·5 |
| Sulphate of iron | ·75 |
| Alumina | ·5 |
| Silica | ·15 |
| —— | |
| Total | 4·65 |
| Great St. George. | |
| Muriate of soda | 1·35 |
| Sulphate of lime | ·74 |
| Carbonate of iron | ·70 |
| Alumina | ·50 |
| Carbonate of lime | ·10 |
| —— | |
| Total | 3·4 |
[165] The discovery of the electrotype has been disputed, as all valuable discoveries are. Without, however, at all disparaging the merits of what had been done by Mr. Jordan, I am satisfied, after the most careful search, that the first person who really employed electro-chemical action for the precipitation of metals in an ornamental form, was Mr. Spencer, of Liverpool.
[166] See Spencer, Instructions for the Multiplication of works of Art in Metal by Voltaic Electricity. Novelties in Experimental Science: Griffin, Glasgow, Elements of Electro-Metallurgy: by Alfred Smee, Esq.
[167] The magneto-electrical machine is employed in Birmingham for this purpose; but I am informed by Messrs. Elkington that they do not find it economical, or rather that the electro-precipitation is carried on too slowly.
[168] This has been done by Mr. Robert Were Fox, at a mine near Falmouth. By connecting two copper wires with two lodes, and bringing them, at the surface, into a cell containing a solution of sulphate of copper, this gentleman obtained an electrotype copy of an engraved copper-plate.