﻿Magnetism and Static Electricity. 299 



of the interference. In other words, if magnetism be dependent 

 on the diamagnetic polarity of the medium surrounding it, any 

 alteration of, or interference with that polarity should likewise be 

 shown in a corresponding alteration of the magnetic force itself. 



A fine darning-needle magnetized to saturation, suspended 

 equatorially by a filament of silk or a fine hair so that it was free 

 to swing horizontally, was the test-needle used in the following 

 experiments. The suspended needle being come to rest, when 

 either the north or south pole was approached by an electrified 

 glass tube, it was attracted by it, and could be made to follow 

 the tube round and round; or if the tube were laid down at 

 such a convenient distance as prevented actual contact, but in 

 the same direction as the magnetic meridian, the needle then set 

 itself perpendicular to the electrified tube, gradually returning 

 to its normal position as the tube's electricity became dissipated 

 through the air or otherwise. 



A stick of sealing-wax or other negative dielectric gave the 

 like result ; or by approaching both cautiously at the same time, 

 the needle was maintained without alteration of position. 



The needle was then itself electrified by contact ; and whether 

 positive or negative electricity were employed, its behaviour was 

 apparently identical with that of a piece of copper wire suspended 

 by a torsion-thread under similar circumstances, being repelled 

 by like, and attracted by unlike or neutral electrics — returning, 

 however, to the magnetic meridian as the electricity became 

 dispersed. 



A horseshoe-magnet with a lifting-power of about three pounds, 

 and which had not been remagnetized for some years, so that its 

 magnetic force might be reckoned as constant, was placed on a 

 level with the suspended test-needle, and at just such a distance 

 that actual contact could not take place betwixt the opposing 

 poles. Of course the needle immediately took up its position 

 with its north pole opposite the south, and the south opposite 

 the north pole of the magnet, the sharp suddenness of its vibra- 

 tions in coming to rest testifying to the inductive power mutu- 

 ally exerted. A body electrically excited being then presented 

 to it, attraction was immediately manifested ; the needle could 

 be drawn bodily away from the magnetic field ; or if the sepa- 

 rate ends were acted on, the north or south pole could be drawn 

 completely round till it was opposite the pole of the magnet of 

 the same name ; or if the needle was itself positively electrified, 

 then repulsion was manifested for positively, and attraction for 

 negatively electrified bodies ; and the opposite behaviour if elec- 

 trified negatively. 



Similar results were likewise obtained when very small quan- 

 tities of static electricity were employed; a piece of sealing-wax 



