Page:Memoirs of the Geological Survey of Great Britain, Volume 1.djvu/461

448 446 INFLUSKCE OF MAGNKTISM ON CBYSTALLIZATION

themselyeB according to some influence which is evidently opposed to the magnetic power. A very extensive series of experiments will be necessary to the elimination of the law of these forces.

35. In every experiment I have been struck with the difference in the quantity of precipitate which collected, or crystals which formed around the two poles of the magnet ; a larger quantity, in all cases, accu- mulating about the north, than about the south pole. This was so veiy different from our preconceived notions of the condition of a magnet, in which we have been led to regard the powers in a state of equilibrium, that it demanded a careful investigation.

36. The superior power of one pole of a magnet has been, I find, on several occasions, mentioned by the elder magneticians, and Bitter published a statement of experiments, corroborated by (Ersted,* in 1828. After stating that its action on frogs was similar to that of a galvanic pair, CErsted says : — '^ Bitter pla^ un fil de fer aimante, dans un plat de fiuence, il y versa de I'acide nitrique tres faible : le p81e meridional fut beaucoup plus fortement attaque par Tacide que le p61e septen- trional, et se trouva aussi entoure d'un depot d'oxide beaucoup plus tot." Other experiments are described in the same paper, but they do not appear to have had that attention paid to them which they deserve, related as they are to a correct knowledge of the magnetic power, and pointing, probably to some law of action which is not indicated by any theory received at present by the scientific world.

37. With a riew of determining the question, I instituted a series of experiments. I intend extending them as &r as possible, with every modification of circumstances which may suggest themselves to me, but at present I am only enabled to announce the following fruits. The method employed by me will be understood frt)m the following figure (Fig. 10).

Iron wires are cemented into glass tubes ; these tubes are filled wiA the substance in solution to be examined, and being inverted in a vessel of the same solution, the projecting ends of the wire are suspended from the poles of a. permanent horse-shoe magnet, by which, of course, these wires, under the influence of induction, become magnets : a north pole being in the solution on one side, and a south pole on the other.

38. When a solution of sulphate of copper was employed, it was found invariably that the largest quantity of copper was deposited about the wire from the north pole : the difference in quantity between that and the metal about the south pole, depending upon the amount of chemical action which is established during the process of substitution.

39. If sulphuric acid was added to the solution of sulphate of copper,

« Annalea d^ Chimie et de Phyiique, toI. xxxtUL p. 197.

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