246 
PROFESSOR, TYNDALL’S FURTHER RESEARCHES 
a shock to the magnets, which, on the disappearance of the currents, would return to 
their original position. But the deflection is permanent, and is therefore due to an 
enduring cause. In his paper on “Supposed Diamagnetic Polarity,” Mr. Faraday 
riglitly observes, — “If the polarity exists, it must be in the particles, and for the time 
permanent, and therefore distinguishable from the momentai-y polarity of the mass 
due to induced temporary currents, and it must also be distinguishable from ordi- 
nary magnetic polarity by its contrary direction.” These are the precise character- 
istics of the force made manifest by the experiments now under consideration. 
Further, the strength of induced currents depends on the conducting power of 
the mass in which they are formed. Expressing the conducting power of bismuth 
by the number T8, that of copper would be expressed by 73‘6% the conductivity of 
the latter being therefore forty times that of the former. Hence the demand made 
by the opponents of diamagnetic polarity, to have the experiments repeated with 
cylinders of copper; for if the effect be due to induced currents, they will show 
themselves in copper in a greatly increased degree. The following is the result of a 
series of experiments made with two copper cylinders, of the same dimensions as the 
bismuth ones already described. 
V. 
Cylinders of Copper. 
Position 1. 754 
Position 2. 754 
Position 3. 755 
Now if the effects obtained with bismuth were due to induced currents, we should 
have the same effects forty times multiplied in the c-ise of copper, in place of which 
we have scarcely any sensible effect at all. 
Bismuth is the only substance which has hitherto produced an action in experi- 
ments of this nature; another illustration, however, is furnished by the metal anti- 
mony, which possesses a greater conductive power, but a less diamagnetic power than 
bismuth. The following results were obtained with this substance: — 
VI. 
Cylinders of Antimony, 
length 3 inches. 
diameter 0*7. 
Current direct t- 
Current reversed J 
Position 1. 
693 
244 
Position 2. 
688 
252 
Position 3. 
683 
261 
* Philosophical Magazine, Series 4, vol. vii. p. 37. 
t As in III. and IV. 1 As in I. and II. 
