Bodies are i spelled from the Poles of a Magnet. 263 



Normal Diamagnetic Bar. — The above experiments exhibit to 

 us the deportment of the normal paramagnetic body under a great 

 variety of conditions, and our next step is to compare with it the 

 deportment of the normal diamagnetic body under the same cir- 

 cumstances. 



For the sake of increasing the force, the helix was removed 

 from its lateral position and placed between the two poles, as in 

 fig. 6, p. 257. The normal diamagnetic bar was suspended 

 within the helix and submitted to the self-same mode of exami- 

 nation as that applied in the case of the paramagnetic body. 



The polarity first excited was that shown in fig. 9, Plate III., 

 and the position of rest, when the magnet alone acted, was at 

 right angles to the line joining the poles ; on sending a current 

 through the helix in the direction of the arrow, the deflection 

 was towards the dotted line. 



Preserving the magnetic polarity as in the last experiment, 

 the direction of the current through the helix was reversed, and 

 the deflection was that shown in fig. 10. 



Reversing the polarity of the magnet, and sending the cur- 

 rent through the helix in the direction of the last experiment, 

 the deflection was that shown in fig. 11. 



Preserving the last magnetic poles, and sending the current 

 through the helix in the opposite direction, the deflection was 

 that shown in fig. 12. 



In the following four experiments the helix was excited first. 



Operated upon by the helix alone, the suspended bar set its 

 length parallel to the convolutions, and perpendicular to the axis 

 of the coil : the direction of the current was first that shown in 

 fig. 13 : when the magnet was excited, the bar was deflected 

 towards the dotted position. 



Interrupting both currents, and reversing the current in the 

 helix ; when the magnet was excited, as in the last experiment, 

 the deflection was that shown in fig. 14. 



Preserving the helix current as in the last experiment ; when 

 the polarity of the magnet was reversed, the deflection was that 

 shown in fig. 15. 



Interrupting both, and reversing the current in the helix ; 

 when the magnet was excited as in the last experiment, the de- 

 flection was that shown in fig. 1 6. 



In a paper on the Polarity of Bismuth* published in the 

 Philosophical Magazine, ser. 4. vol. ii., and in Poggendorff"'s 

 Annalen, vol. Ixxxvii., an experiment is recorded in which the 



* From the notices of this paper which have aj)peared in the continental 

 journals, I am obliged to infer that it is in some respects obscurely written. 

 The conclusion I intended to express is that bismuth possesses a polarity 

 ojjposed to that of iron. — J. T. 



