Page:Memoirs of the Geological Survey of Great Britain, Volume 1.djvu/463

450 450

INFLUENCE OF VOLTAIC ELECTRICITY

stant, have such an important bearing on the subject of this paper, that I have thought it advisable to describe these experiments. The laws of magnetic action, as they are distinguished, if different, from thoee of voltaic electricity, it is most important to learn. This great force, as developed in nature, and exhibited in all the phenomena of terrestrial magnetism, must influence the conditions of structure, and the arrange- ments of the masses of the rocks constituting the crust of the earth.

42. It occurred to me that the position of the wires might have much to do with the observed differences. Experiments were therefore made in which the magnets were inverted, and also in which they were placed in the magnetic meridian in the direction of the dip. The results were, however, under all these circumstances the same, the largest quantity of metal appearing at the north ; the greatest measure of hydrogen gas being found in all cases at the south pole.

B. — INFLUENCE OP VOLTAIC ELECTRICITY.

43. The earliest experiments with which I am acquainted, showing the tendency of electrical currents to produce a determinate arrange- ment in the particles of matter, were by Mr. R. Were Fox and Mr. Thomas Jordan.* Of these the following experiments must be con- sidered merely a repetition, but they have been extended from clays which were the only materials on which they operated, to sandstones, plaster of Paris, and other substances. The manner in which these ex- periments were tried, will be understood from tiie foUowmg description of the arrangements employed. An oblong box was divided in the centre

Fig. 11.

by a wall of clay (c) three or four inches in thickness, or by any other body on which it was thought desirable to try the experiments. A zinc and copper plate (a b) connected by a band of copper was then passed down into the box on either side of the clay, and the voltaic pair brought

p. 169. The Tiew entertained by Mr. Fox will be gathered from the following :— '< Indeed, the general laipinated structure of the clay appears to indicate that a series of Toltaic poles were produced throughout the clay, the symmetrical arrangement of which had a cor- responding effect on the structure of the clay. *
 * Reports of the Royal Cornwall Polytechnic Society, No. 5, 1837, p. 68; No. 6, 183S,

Digitized by

Google