AND STRAIN ON THE ACTION OF PHYSICAL FORCES. 
147 
Experiment LXV. 
A piece of the same iron as had been used in Experiment LXII. was tested with 
one Grove’s cell and no external resistance save that of the magnetizing coil for the 
M.C., and three Grove’s cells with adjustable external resistance for the B.C. 
B.C. in terms of the divisions 
of the scale of the tangent 
galvanometer. 
Increase per unit of resistance. 
M.C. = 109 divisions of the 
scale of the 
tangent galvanometer. 
130 
■000300 
940 
■000316 
1521 
■000353 
In this experiment, which was conducted in the same manner as Experiment LXII., 
there is evidently a greater alteration produced by magnetism when the B.C. has a 
high value than when it has a low one, and the differences between the different 
values in the second column are certainly larger than could be attributed to errors of 
observation. Now in Experiment LXVIII. it will be shown that with unannealed 
steel, and in Experiment LXI. it has been shown with annealed nickel, that there is 
little or no difference in the amount of alteration of resistance effected by magnetism 
when the B.C. is made to vary in amount; and the reason is apparent, for with the 
nickel and the steel there was no* appreciable difference between the induced currents 
caused by the magnetization of these metals when the B.C. was flowing and when it 
was not, whereas, if we turn to the second, third, and seventh columns of Table XXVIII., 
we see that there is a very appreciable difference in the case of the annealed iron wire, 
between the induced currents with and without the B.C. 
All these experiments are in direct contradiction to those of Auerbach, but yet it 
was thought fit to try others with annealed pianoforte-steel wire. 
Experiment LXVI. 
A piece of annealed pianoforte-steel wire, 10 centims. long and. ’085 centim. in 
diameter, was tested with various battery-power from one to four Grove’s cells for the 
B.C., and battery-power varying from one Grove’s cell with a resistance of 10 ohms 
in the external circuit besides the resistance of the coil A, to seven Grove’s cells with 
no external resistance save that of A for the M.C. 
In no case was a diminution of resistance produced by magnetization. With one 
Grove’s cell for the B.C., and seven Grove’s cells for the M.C., an increase of 
resistance of *0585 per cent, was observed : lower values of the M.C. gave smaller 
and smaller results as the M.C. diminished. The alteration of resistance produced 
by unit magnetizing force was estimated in the usual manner to be 1500 X 10 -8 per 
unit. 
That is, no difference of sucli an amount as to make it seem worth while at the time to record it. 
U 3 
