AND STRAIN ON THE ACTION OF PHYSICAL FORCES. 
139 
established. The effect of magnetization on the resistance was tested when loads of 
0, 6, 10, and 12 kilogs. were on the wire. The M.C. was produced by five 
Grove cells. 
Tangent of the 
deflection of the needle 
of the tangent galvanometer. 
Load in kilogs. on 
the wire when under 
magnetization, the scale 
pan weighing 2 kilogs. 
not included. 
Alteration of resistance 
produced by magnetization 
in divisions of the 
galvanometer-scale; one 
division representing 
an alteration of '0005 per cent. 
0 
27 
•247 
6 
19 
10 
25 
12 
25 
Both these experiments show that the increase of resistance which was produced by 
the longitudinal magnetization is lessened by temporary stress up to a certain limit of 
the latter, and several other experiments of a similar kind proved that after the 
diminution of alteration of resistance caused by magnetization had reached a maximum, 
further temporary stress began to reverse the first effect, sometimes only just before 
the “ breaking-load ” of the wire had been reached. In no case, however, was dimi¬ 
nution of resistance caused by longitudinal magnetization for the highest stress which 
could be put upon the wire without breaking it, 4 ' and this, too, when strengths of 
current of very different degrees were tried. 
Experiment LXI. 
An annealed nickel wire, '105 centim. in diameter, was arranged in the same manner 
as the non wire in the last experiment; but the clamps a and c (fig. 19) were placed 
nearer together, and just inside the coil A, so that the whole of the nickel experimented 
on would be under the influence of the magnetizing force. In this case the coolers, S S, 
were dispensed with, and, instead, the wire to be tested was provided with a solenoid 
of fine silk-covered copper wire, wound in two layers on a glass tube of the same 
length as that of the nickel wire under examination, and of a diameter such that the 
latter could be easily slipped inside it. This solenoid served, when required, to give 
the relative amounts of magnetism imparted to the steel by the different magnetizing 
forces. The alterations of resistance produced by the magnetism were first determined, 
then the galvanometer having been disconnected from the “ bridge” and joined up with 
the solenoid, the induced currents caused by the magnetization were measured by the 
* This was rather unexpected; since Joule has shown (Phil. Mag., 1847, vol. xxx., pp. 76, 225) that 
whilst iron free from stress is increased in length by longitudinal magnetization, yet when loaded beyond 
a certain limit its length is diminished by the same cause. 
T 2 
