INTENSITY OF MAGNETIC AND DIAMAGNETIC FORCES. 749 



IV. The watch-glass I'aised 5"5 millims. : — 



Number of cells 8 Attraction 

 1 



V. The watch-glass raised 8*5 millims. : — 



Number of cells 8 Attraction 



1 



By merely comparing a couple of the data from the pre- 

 ceding observations, it is seen how, with the same suspension 

 of the \vatch-glass containing the piece of bismuth, the entire 

 mass, at a distance of 3*5 above the poles, is diamagnetically 

 repelled and magnetically alb-acted with nearly equal force, ac- 

 cording as the current is excited by tight or four cells ; fur- 

 ther, that the magnetic attraction increases considerably when 

 the electro-magnets are weakened by using only a single cell 

 instead of four cells. It is also distinctly evident how a greater 

 distance from the poles, corresponding to a diminution of the 

 power of the electro-magnets, produces the same effect. When 

 magnetic attraction exists with a given strength of current, 

 we do not obtain the greatest effect nearest to the poles ; on 

 the contrary, this greatest effect takes place at a considerable 

 distance from them ; it decreases even to evanescence by approxi- 

 mation to the poles of the electro-magnet if the latter is suffi- 

 ciently powerful, and then, by continuing the approximation, 

 diamagnetic repulsion is apparent, which constantly increases till 

 the glass is in contact with the poles. On employing eight 

 cells, the point of indifference is situated at a distance of about 

 4 millims. from the poles, and with four cells from 1 millim. to 

 2 millims. nearer to the poles. The maximum magnetic effect 

 appears in both cases, at least with eight cells, not to be attained 

 with a distance of 8 millims. 



53. In perfoi'ming the preceding experiments, we constantly 

 observe, that, even in the case of the most decided diamagnetic 

 effect, at the moment of closing, no repulsion, but rather a very 

 evident attraction, occurs, and that this is converted into repul- 

 sion only after the lapse of some time. The explanation of this 

 phaenomenon must be sought for in the fact, that when the cir- 

 cuit is closed the power of the magnet attains its entire strength 

 only after a certain time, and not instantly. The observation in 

 question is consequently a fresh confirmation of our law. 



54. All the phaenomena described, with all their modifications, 



VOL. V. PART XXI. 3 E 



