WITH MAGNETISM AND ELECTRICITY. 185 



were observed, while 4:he arc of oscillation was multiplied by the 

 alternate elevation and descent of the bar of bismuth, the fol- 

 lowing results were obtained : — 



Elonga- Arc of 



" tion. oscillation. 



With current, bismuth in the middle ^00-0 



„ bismuth above 407.0 ^'^ 



„ bismuth below 'iiCo ^^^ 



„ bismuth above 4«i.^ ^^'^ 



„ bismuth below *;i^.^ ^^'^ 



,_, bismuth above Aha-f^ ^^*^ 



„ bismuth below ^90'-^ ^^'^ 



„ bismuth above A^'x-a ^^'^ 



„ bismuth below Wo-O "^^'^ 



„ bismuth above ATi'n 51'0 



„ bismuth below e^ia-n ^^'^ 



,, bismuth above "o c 57*5 



" 468*5 



A little bar of iron, suspended instead of the bismuth, when 

 situated above, caused the magnet to move to higher numbers, 

 and when below caused it to move to smaller numbers ; the 

 same was observed when the little bar was reversed. The stand 

 of the instrument must be very heavy ; a serpentine stone was 

 found very suitable : the bismuth must be capable of moving 

 freely, and the copper wire pure. In all observations it was 

 found, that applying four of Grove's elements, when the bismuth 

 was drawn ujp, the impulsion amounted to from 8'9 to 9*4 divi- 

 sions of the scale, the direction being towards smaller numbers, 

 while a fine iron wire under the same conditions caused the 

 magnet to move towards higher numbers ; further, that the bis- 

 muth without a current acted as an iron wire, and caused a motion 

 through 5 to 7*5 divisions of the scale. When the latter action 

 is taken into account, the mean diamagnetic impulsion of the bis- 

 muth by the application of four of Grove's elements is found 

 = 15*4 divisions of the scale. By multiplication, the arc of 

 oscillation could.be increased to 57*5 divisions, and retained at 

 this magnitude, inasmuch as the action of the copper damper 

 which surrounded the magnet held the diamagnetic action in 

 equilibrium." 



The following series of experiments was made with an appa- 

 ratus somewhat different from that just described ; a particular 



