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X. Experimental Researches in Magnetism. 
By Professor J. A. Ewing, B.Sc., F.R.S.E., University College, Dundee. 
Communicated by Sir William Thomson, F.R.S. 
Received December 5, 1884,—Read January 8, 1885. 
[Plates 57-68.] 
§ 1. The experiments to be described in this paper deal with a number of parts of one 
general subject—the magnetisation of iron and steel. They relate to— 
(1.) The magnetic susceptibility of iron and steel; the form of the curve of magne¬ 
tisation and magnetising force; and the changes of magnetism caused by 
gradual reversal and other cyclic changes of magnetising force. 
(2.) The influence of vibration on magnetic susceptibility and retentiveness. 
(3.) The influence of permanent strain on magnetic susceptibility and retentiveness. 
(4.) The energy expended in producing cyclic changes of magnetisation. 
(5.) The ratio of residual to induced magnetism. 
(6.) The changes of induced and residual magnetism caused by changes of stress. 
(7.) The effects of constant stress on magnetic susceptibility and retentiveness. 
(8.) The changes of magnetism caused by changes of temperature. 
(9.) The effects of temperature on magnetic susceptibility. 
In connexion with the above, experiments of a closely related character have been 
made on the following additional subjects, but an account of them will be reserved for 
another paper:— 
(10.) The changes of thermoelectric quality caused by changes of stress. 
(11.) The changes of thermoelectric quality caused by magnetisation.* 
* The following previous publications may be referred to as preliminary notices of some of the 
results:— 
(1.) “ Effects of Stress on the Thermoelectric Quality of Metals ” (Abstract), Proc. Roy. Soc., No. 214, 
1881, p. 399. 
(2.) “ On Effects of Retentiveness in the Magnetisation of Iron and Steel,” Proc. Roy. Soc., No. 220, 
1882, p. 39. 
(3.) “On the Magnetic Susceptibility and Retentiveness of Iron and Steel,” Brit. Ass. Rep., 1883, and 
Phil. Mag., Nov., 1883. And an intimately related investigation is described in a paper “ On the Produc¬ 
tion of Transient Electric Currents in Iron and Steel Conductors by Twisting them when Magnetised, or 
by Magnetising them when Twisted,” Proc. Rov. Soc., No. 228, 1883, p. 117. 
