640 
PROFESSOR J. A. EWING ON MAGNETISM. 
who, both by his own work and by his analysis of the w T ork of others, has contributed 
enormously to our knowledge of magnetism, and the paper of Chrystal, to which 
allusion has been made, render some parts of this task at once comparatively easy 
and almost unnecessary. But contributions continue to be added at a rate which 
soon makes the best summary incomplete, and, to a greater extent than I am aware, 
some of the results of this paper may be repetitions of work already published. Even 
then, however, I hope they may not be without value, on account of the facts (l) that, 
with the single exception of the experiment of § 121, the magnetisation dealt with 
has been as nearly uniform as it is practicable to have it, and (2) that very nearly all 
the observed values of magnetism and magnetising force have been reduced to 
absolute measure. It may be added that the subject with which this paper deals has, 
in addition to its scientific interest, a special practical importance at the present time, 
on account of its very obvious bearing on many points relating to the industrial 
applications of electricity, and particularly to the design of dynamo-electric machines. 
§ 123. The work described in this paper was done during 1881-1883 in the 
Physical Laboratory of the University of Tokio, Japan, with the help of four Japanese 
students, without whose assistance, both in the taking of observations and in the 
arithmetical labour of reducing them, it would have been impossible for me to have 
covered so much ground. To Mr. R. Fujisawa and Mr. S. Tanaka I am particularly 
indebted for help in the first part of these experiments—the examination of the 
relation of 2> to during the application and cyclic change of <§, by the ballistic and 
magnetometric methods,—and to Mr. A. Tanakadate for help in the second part — 
the investigation of the effects of stress on magnetism. These gentlemen threw 
themselves into the work with a thoroughly intelligent interest and with the utmost 
zeal. In the last part of the paper—on the effects of temperature on magnetism—the 
observations wdiicli are quoted w'ere for the most part taken under my direction by 
Mr. S. Sakai, who prosecuted this difficult portion of the subject with much per¬ 
severance, and to whom I am also indebted for valuable help in another investigation 
— of the effects of stress and magnetisation on the thermo-electric quality of iron—the 
results of which remain to be described. Those results, which are closely related to 
some parts of the foregoing inquiry, will form the subject of another paper. 
