22 
PROFESSOR TYNDALL ON THE DIAMAGNETIC FORCE, ETC. 
whose experiments first showed that the repulsion of diamagnetic bodies follows the 
same law as the attraction of magnetic ones. 
Bar of sulphur. 
length 25 millims. 
weight 840 milligrms. 
Squares of the Quotients of the repulsions 
magnetic intensities. by the magnetic intensities, 
36-58 0-902 
27-60 0-929 
26-84 0-906 
16-33 0-920 
The constancy of the quotient in the second column proves that the ratio of the 
repulsions to the squares of the magnetic intensities is a ratio of equality. 
I will also cite a series of experiments by Mr. Joule*, which he adduces in con- 
firmation of the results obtained by M. E. Becquerel and myself! 
Bar of bismuth. 
Strength of magnet. Repulsions. 
1 V 
2 2 ^ 
4 4^ 
Let us contrast these with the results obtained by the same gentleman, by permit 
ting the magnet to act upon a hard magnetic needle. 
Magnetic needle. 
length T5 inch. 
Strength of magnet. Attraction. 
1 1 
2 2 
4 4 
Here we find experiment in strict accordance with the theoretical deduction stated 
at the commencement of the present chapter. The intensity of the magnetism of the 
steel needle is constant, for the steel resists magnetization by influence ; the con- 
sequence is that the attraction is simply proportional to the strength of the magnet. 
A consideration of the evidence thus adduced from independent sources, and ob- 
tained by different methods, must, I imagine, render the conclusion certain that 
diamagnetic bodies, like magnetic ones, exhibit their phenomena in virtue of a state 
* Phil. Mag. 4th Series, vol. iii. p. 32. 
