THE GERM OF THE ELECTRIC MOTOR. 49 



" Sometimes, too," he says, "it happens that the nature 

 of iron is repelled from this stone, being in the habit of 

 flying from and following it in turns." 



The allusion is now, not to the current which flows 

 through the rings, but to the influence of the stone upon 

 the iron, merely placed in its neighborhood or, as we 

 now say, in its "field offeree" and not in contact with it. 

 He is describing the turning of the ring, so as first to pre- 

 sent one pole to the lodestone and then the other, for a 

 ring usually has its poles located diametrically opposite 

 each other. If the ring were supported so that its poles 

 could be thus alternately presented to one and the same 

 pole of the lodestone, then, whenever the ring pole was of 

 the same name as that of the lodestone [as north pole to 

 north pole, or south pole to south pole], the ring would be 

 repelled, and would swing away from the lodestone ; but 

 if the ring pole were of different name from that of the 

 lodestone [as north pole to south pole, or south pole to 

 north pole], then the ring would be drawn to the lode- 

 stone, and if the latter were moved, the ring would follow 

 it. Hence, by turning the ring to and fro, as on an axis, 

 it could thus be made to swing or vibrate backwards or 

 forwards in front of the lodestone, or, as Lucretius ex- 

 plains, the ring will fly from or follow the stone "in 

 turns." Here is the first foreshadowing of the motion of 

 an armature for such is the ring before the pole of a 

 magnet, by change in relative polarity of magnet and 

 armature ; in the light of present knowledge we might 

 even regard this as the advent into the world of the con- 

 version of the energy of electricity into mechanical motion, 

 and the germ of the electric motor. 



Lucretius says, further, that he has seen the Samothra- 

 cian rings "jump up" when the magnet stone had been 

 "placed under." It is unquestionably true that in a sus- 

 pended chain of rings, as he describes, the pole at the bot- 

 tom of the lowest ring would be of the same name as that 

 of the pole of the supporting lodestone say, north. If 



