60 Trans. Acad. Sci. of St. Louis. 



large bar magnet placed on the opposite side of the 

 needle. The needle was rendered sensitive to changes 

 in the turning moment of the wire magnet, by partially 

 compensating the effect of the earth's field by means of 

 bar magnets on either side of the needle. The time of 

 a complete vibration in the earth's field within the build- 

 ing was the same, when all magnets were removed as 

 when the opposing deflection magnets were in place, 

 namely, 8.94 seconds. The compensating magnets in- 

 creased the vibration period to 20 seconds. 



It was found when either terminal of the influence 

 machine in an adjoining room was connected with the 

 insulated wire magnet, the other terminal being 

 grounded, that the deflecting effect of this magnet was 

 increased. The angle of deviation could not be deter- 

 mined with any precision, on account of fluctuations in 

 the needle, but it amounted to about 15 minutes of arc. 

 In some of the earlier experiments the reverse result 

 was obtained. It was then concluded that the attraction 

 between magnets, like that between masses of matter, 

 depends upon their electrical potential. This question 

 is, however, still an open one. It was found when the 

 air around the magnet is rendered as quiet as possible, 

 and when no disruptive effects are permitted along the 

 conductor, that the magnet becomes apparently stronger. 

 It was also found that disturbances of the air around the 

 magnet appeared to diminish its deflection effect. It was 

 found when the charged magnet was covered with tin- 

 foil, that the change in the defection due to electrifica- 

 tion was apparently unchanged. It was found when the 

 air around the magnet was disturbed by the movement 

 of an assistant, or by means of a palm-leaf fan, that its 

 deflecting effect due to electrification was diminished. 

 When the fan was operated during alternate semi-vibra- 

 tions of the needle, the oscillations of the needle could 

 be gradually increased in amplitude to five or six degrees 

 of arc. 



