Page:Proceedings of the Royal Society of London Vol 4.djvu/343

 Rh

The Right Honourable Lord Crewe, James Alderson, M.D., and Edward James Seymour, ALD., were balloted for, and duly elected into the Society.

The following papers were read, viz. —

1 . " Experiments on the electric conditions of the Rocks and Metalliferous Veins (Lodes) of Longclose and Rosewall HiU Mines in Cornwall." By William Jory Kenwood, Esq., F.R.S,, &c., Se- cretary of the Royal Geological Society of Cornwall.

The experiments, of which the results are given in this paper, were undertaken with the view of determining whether it was in conse- quence of the imperfections of the galvanometers, or other apparatus, employed, that Mr. R. W. Fox, and other experimenters, had been unable to detect the presence of electricity in the tin veins of Corn- wall. The mode of experimenting was in principle the same as that pursued by Mr. Fox, namely, that of placing plates of metal in con- tact with the points to be examiaed, carrying wires from the one to the other, and interposing a galvanometer in the circuit. The plates employed were of sheet-copper and sheet-zinc, and they were about six inches long, and three inches and a half wide. The wires were of copper, one twentieth of an inch in diameter, and the same that had been used by Mr. Fox.

The tabular results of these experiments show that both the gra- nite and the tin vein at Roseivall Hill mine, and also the greenstone and the copper vein in that of Longclose, present unequivocal traces of electric currents, whether different parts of the same veins or va- rious portions of the same rocks were examined.

It also appears, from these experiments, that the nature and positions of the small metallic plates employed materially affect, not only the intensity, but in some cases also the directions of the currents; and also that there is a considerable difference in the results when the same plates of metal are placed on different ingredients in the veins, even though these may be in immediate contact with each other.