Page:Memoirs of the Geological Survey of Great Britain, Volume 1.djvu/467

454 454 INFLUENCE OF VOLTAIC ELECTRICTTY

with that observed in the clay (46). On the zinc side the laminatioiis extended to this Kne of fracture, and the consolidation on the other side was also stopped by it Running from end to end of the brick, about an inch within it, on the zinc side, a line of carbonate of copper was traced, above and below which some lines of lamination were also marked out, as though this line of a metallic salt had become the centre of a new set of influences. At each end of the mass a great number of well- marked curved lines were observed, passuig from the plates on either side to the fracture. This indication of a movement of the particles of the solid mass in determinate lines helps to explain the cause of the dislocation. The general tendency of the current being along these lines, lamination occiuring on one side of the mass, at right angles to them, and consolidation on the other, in the line of the current, we can easily perceive that the line of dislocation must occur at a tangent to these curves, at that point where the two influences neutralize each other, which will be found to be, in a square mass, from near one of its upper angles to one of its lower angles, the exertion of electrical fbroe being evidently across the imperfect conductor, but in lines of greater or less ciu-vature, according to the reustance its particles otkr to the passage of the voltaic power.

52. In the experiment just described, there was formed, during the long-continued action, a sheet of oxide of copper between the copper plate and the sandstone. This, on the ade nearest tfie copper, was entirely the black oxide, beneath which appeared some carbonate of the metal. On the inside it was covered with lamiruB of oxide of zinc, alternated with the black oxide of copper, across which, in a very decided manner, curved lines of the same order as those observed on the brick were seen, indicating most plainly the same general directioD along the entire length of the brick as was observable at the ends.

53. Finely-powdered coal was placed between the plates, sulphate of iron being employed fer the purposes of electrical excitation. Hie experiment has been some months in action, and we learn firwi it Ihe curious and important fieu^t, that peroxidation of the iron is prevented by the presence of carbon. Evidences of lamination present themselves, but it is thought desirable to allow the continuance of the voltaic action for some time longer.

54. Although the experiments named are important in themselves, as expressive of individual facts, it is of course necessary that they shoidd be repeated under various modifications before we can attempt to draw any extended generalizations ftom them. Upon considering, however, the results arrived at in the experiments on magnetic curves, it will now, I think, be evident that the particles of matter constituting the clay, sandstone, &c., arrange themselves according to the law of diai*

Digitized by

Google