PHYSICS OF NINETEENTH CENT. ELECTRICITY 563 



FIG. 275. ANDRE-MARIE AMPERE. 



ANDRE-MARIE AMPERE (1775 1836) had no sooner heard of 

 CErsted's discovery than he proceeded by ingeniously contrived ex- 

 periments to extend and supplement it. If the fixed wire conveying 

 a current attracts or repels a magnetic pole, a movable wire conveying 

 a current may be expected to exhibit movements when a magnetic 

 pole was brought near it. Ampere not only discovered that such was 

 the case, but that similar forces were in action between currents. The 

 mode in which he was able to render mobile the conductor conveying 

 a current will be understood from Fig. 276, where c and D are two 

 horizontal metallic supports through which the current circulates in 

 the direction shown by the arrows. Each support terminates in a 

 small iron cup, one cup being vertically below the other. The ends 

 of the mobile conductor terminate in points or pivots, one of which 

 turns in the upper cup, and the other in the lower cup. In each cup 

 a globule of mercury is placed to insure perfect metallic contact The 

 mobile conductor A A has in the figure a circular form, but it may be rect- 

 angular or of other forms. Now, Ampere found that when another 



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