The magnetic nature of flames and gases has been also studied. When the flame of a candle is brought between the poles of a magnet, it is repelled by them, and thrown out horizontally into an equatorial position. To ascertain the magnetism of gases, Faraday inflated soap-bubbles with them, and their pars- or diamagnetism was exhibited by their being attracted or repelled by the poles. Ile ascertained the same by causing the gases to flow out from glass tubes in the presence of the poles, when the peculiar magnetism of the gas was shown by its choosing an axial or equatorial menus of egress.
The following list gives the kind of magnetism displayed by the more common sub stances: Paramagnetic.—Iron, nickel, cobalt, manganese, chromium, titanium, palladium, paper, sealing-wax, peroxide of lead, plumbago, red-lead, sulphate of zinc, shellac, vermilion, charcoal, proto and per salts of iron, salts of manganese, oxygen, air.
Diamagnetie.—Bismuth, antimony, zinc, tin, cadmium, sodium, mercury, lead, silver, copper, gold, arsenic, uranium, tungsten, rock-crystal, mineral acids, alum, glass, litharge, niter, phosphorus, sulphur, resin, water, alcohol, ether, sugar, starch, wood, bread, leather, eaoutchouc, hydrogen, carbonic acid, coal-gas, nitrogen.
The nature of the medium in which the body under examination moves, exerts a powerful influence on the nature and amount of the magnetism it exhibits; thus, if a glass tube be filled with a solution of the proto-sulphate of iron, and suspended between the poles, it will place itself axially. It will do the same if made to move in water, or
a solution more dilute of the peoto-sulphate of iron. It will be indifferent in a solution of the same strength; but it will place itself equatorially in a stronger solution. Thus, the same substance may appear paramagnetic, indifferent, or diamagnetic, according to the nature of the medium in which it moves. As a general rule, a body shows itself paramagnetic towards one less paramagnetic than itself, indifferent towards one equally magnetic, and diamagnetic towards one more paramagnetic than itself. The same takes place, mutatis mutandis, with diamagnetic substances. This has given rise to the theory, that there is no such thing as diamagnetism per se, and that bodies are diamagnetic only in media of greater paramagnetic power than their own. This view of the ease is, how ever, rendered highly improbable from the fact, that diamagnetism is exhibited as decidedly in a vacuum as in any medium, and a vacuum cannot be supposed to possess magnetic properties of any kind.