Electricity. 343 



had a third body mounted on a stand and supported by an upright rod 

 of very elastic steel, which was easily swayed by the slightest force. 

 This he placed under the water and moved about from one part of the 

 vessel to another, noting the manner in which it was affected by the cur- 

 rents of the water set up by the vibrations of the drum heads. When a 

 single drum vibrated, the effect at a little distance was lines of force 

 radiating from the axis, like the spokes of a wheel, and imitating the 

 magnetic lines seen end-on as shown in fig. 132. When the two drums 

 were placed a little ways apart, in the same line or axis, and vibrated in 

 opposite phases the} 7 acted just like a complete magnet, and the lines 

 formed in the water currents took the form of the magnetic lines of force 

 shown in fig. 131. Other experiments showed the same lines which in 

 magnetism are lines of repulsion and which follow the bringing of two 

 poles of the same name near each other. This occurred when the two 

 drums were operated in the same phase, both bulging out at the same 

 instant. But the drums instead of repelling, attract each other when 

 they vibrate in the same phase. Fig. 147 shows the lines of magnetic 

 force when the north poles of two magnets are brought near each other. 



FIG. 147. Showing lines of Repulsion of 

 Similar Poles of Magnets. 



FIG. 148. Showing lines of Attraction of 

 Unlike Poles of magnets. 



The same happens if both are south 

 poles. The lines of force both rush- 

 ing out together meet and deflect each 

 other. As they tend to straighten 

 from this compulsory bending, the 

 effect is repulsion. The lines of force 

 between the north pole of one magnet 

 and the south pole of another, as as- 

 certained by the position taken by 

 iron filings sifted between them when 

 they are brought near each other, are 



%l'^^^ ; ^/^^ shown in fig. 148. These lines are 

 FiGs^i^ANit 148 ^ closely imitated by the water currents 



when the drums are vibrated in opposite phases. In other experiments 

 Prof. Bjerkness showed in the water the same sort of motions as exhibited 

 by electricity in the formation of whirls of force such as shown in figs. 

 133 and 134. The behavior of two electrical currents when near each 

 other was also imitated ; and in short about all the known lines of force 

 emanating from magnetic or electrical agency, can be imitated by water 

 currents when set in motion by vibrating or pulsating bodies. The at- 

 traction of the drums for each other takes place when they vibrate in 

 the same phase, and they repel when they vibrate in opposite phases, 

 that is, when one is caving in when the other is bulging out. 



