712 
SIR WILLIAM THOMSON ON THE 
of these two effects (that is to say, a smaller effect) on the reversal of the current than 
when it was un-pulled. 
197. The investigation is being continued with special arrangements to discover the 
explanation of the seeming anomalies described above, and with the further object of 
determining in absolute measure the amounts of all the ascertained effects, at different 
temperatures up to 100° Cent. It is needless to give in the mean time any minute 
details of the experiments already made on the soft-iron wires by which the results now 
described were obtained. 
ABSTRACT OF THE PRECEDING PAPER. 
Weber’s method, by aid of electromagnetic induction and a “ballistic galvanometer” 
to measure it, which has been practised with so much success by Thalen, Roland, and 
others, has been used in the investigation of which the results are at present communi- 
cated ; but partial trials have been made by the direct magnetometric method (deflec- 
tions of a needle), and this method is kept in view for testing slow changes of magneti- 
zation which the electromagnetic method fails to detect. 
The metals experimented on have been steel pianoforte-wire, of the kind used for 
deep-sea soundings by the American Navy and British cable-ships ; and soft-iron wires 
of about the same gauge, but of several different qualities. 
I. Steel 
The steel wire weighs about 14^ lbs. per nautical mile, and bears 230 lbs. Weights 
of from 28 lbs. to 112 lbs. were hung on it and taken off, and results described shortly 
as follows were found : — • 
(1) The magnetization is diminished by hanging on weights, and increased by taking 
the weights off, when the magnetizing current is kept flowing. 
(2) The residual magnetism remaining after the current is stopped is also diminished 
by hanging on the weights, and increased by taking them off. 
(3) The absolute amount of the difference of magnetization produced by putting on or 
taking off weights is greater with the mere residual magnetism when the current is 
stopped than with the whole magnetism when the magnetizing current is kept flowing. 
(4) The changes of magnetization produced by making the magnetizing current always 
i:i one direction and stopping it are greater with the weights on than off. 
(5) After the magnetizing current has been made in either direction and stopped, 
the effect of making it in the reverse direction is less with the weights on than off. 
(6) The difference announced in (5) is a much greater’ difference than that in the 
opposite direction between the effects of stopping the current with weights on and 
weights off, announced in (4). 
(7) When the current is suddenly reversed, the magnetic effect is less with the 
weights on than with the weights off. 
