On the Multiple Proportions of the Atomic Weights of Elementary Substances in relation to the Unit of On a Magnetometer for showing the Influence of Tem- JAN 24 1895 LIBRARY. The Locisty H. H. Hayter. Statistical Register of the Colony of Victoria, 1892. The Radcliffe Trustees. Radcliffe Catalogue of 6424 Stars for the Epoch 1890. The Clarendon Press. The Sacred Books of the East. Vols. XXXV., XXXVI., XLIX. Edited by F. Max Müller. HENRY WILDE, F.R.S., President, in the Chair. The thanks of the members were voted to the donors of the books upon the table. Reference was made to the loss by death, since the last meeting, of four honorary members of the SocietyProfessors HELMHOLTZ, MARIGNAC, KUNDT, and ROSCHER. There was a brief discussion on the alleged discovery by Lord RAYLEIGH and Professor RAMSAY of a hitherto unknown gas in the atmosphere; and on the experiments of M. MAXIM with his flying machine. Mr. HENRY WILDE, F.R.S., read a paper on "A Magnetometer for showing the influence of temperature on the magnetization of iron and other magnetic substances," which was illustrated by successful experiments. On a Magnetometer for showing the Influence of Temperature on the Magnetisation of Iron and other Magnetic Substances. By Henry Wilde, F.R.S. (Received October 2nd, 1894). It is not a little remarkable that, in this age of active experimental research, there should be any doubt as to the influence of temperature on the magnetic power of iron and other magnetic substances; yet, from the 17th century to the present time, the most discordant opinions have prevailed on this subject. Barlow, in the year 1822, found that the magnetic power of bars of iron which he experimented upon, as measured by the deflections of a compass needle, increased with the temperature up to a dull red heat, at which it was the strongest; but, at a bright red heat, all magnetic action of the iron suddenly disappeared.* Scoresby, Christie, and others, have also noted a similar increase in the magnetic power of iron with increase of temperature, when measured by the same means. Faraday, on the other hand, described experiments to show that the magnetic power of iron diminished with increase of temperature. He also found that iron at a bright red heat was not entirely insensible to the action of large magnetising forces. More recently, Rowland† and Hopkinson, by the employment of electro-dynamic methods and the needle indications of Barlow, have also found an increase in the magnetic power of iron with increase of temperature. . Phil. Trans., 1822, p. 117. + Phil. Mag., 1874, Vol. LXVIII., p. 321. Phil. Trans., A, 1889, Vol. CLXXX., p. 443 These experimenters were, however, the first to recognise that the apparent increase of the magnetic power of iron, up to the dull red heat, only held good for small magnetising forces, and, further, they found with Faraday, that the power diminished for large magnetising forces with ascending temperatures. Rowland extended his observations to the magnetisation of nickel and cobalt, and found that the magnetic behaviour of these metals with increase of temperature was the same as he had observed in iron. Experiments have also recently been made by Rücker on the effects of temperature on the natural magnet (magnetite), and he has found that the magnetic power of this mineral apparently increases with ascending temperature. A later pronouncement on this subject was made by the President of the Royal Society (Sir G. G. Stokes) in the year 1890, in the course of his anniversary address, in which he stated that, it was generally believed that the susceptibility or magnetisation of iron decreased with the temperature, but, on the contrary, it had been recently. found that the susceptibility was enormously increased with ascending temperatures.* This generalisation was afterwards limited, through my representations, to the action of small magnetising forces.† In my paper on "The Unsymmetrical Distribution of Terrestrial Magnetism," it was shown that by heating small surfaces of the thin sheet iron covering the ocean areas of the mapped globe, strong polarity was induced at the junction of the heated parts, just as when the magnetic continuity of the iron was interrupted by cutting through the same parts of the iron in an equatorial direction. Although this experiment appeared to me to demonstrate, conclusively, that the magnetic power of iron was reduced at * Nature, Dec. 11th, 1890. |