120 THE SCIENTIFIC PAPERS OF 



into electrical force ; and the result obtained by this experiment is 

 remarkable, not only because it demonstrates this hitherto unre- 

 cognized fact, but also because it provides a simple means of 

 producing very powerful electrical effects. 



The apparatus employed in this experiment is an electro-mag- 

 netic machine consisting of one or more horseshoes of soft iron 

 surrounded with insulated wire in the usual manner, of a rotating 

 keeper of soft iron surrounded also with an insulated wire, and of 

 a commutator connecting the respective coils in the manner of a 

 magneto-electrical machine. If a galvanic battery were connected 

 with this arrangement, rotation of the keeper in a given direction 

 would ensue. If the battery were excluded from the circuit and 

 rotation imparted to the keeper in the opposite direction to that 

 resulting from the galvanic current, there would be no electrical 

 effect produced, supposing the electro-magnets were absolutely free 

 of magnetism ; but by inserting a battery of a single cell in the 

 circuit, a certain magnetic condition would be set up, causing 

 similar electro-magnetic poles to be forcibly approached to each 

 other, and dissimilar poles to be forcibly severed, alternately, the 

 rotation being contrary in direction to that which would be pro- 

 duced by the exciting current. 



Each forcible approach of similar poles must augment the mag- 

 netic tension and increase consequently the power of the circulat- 

 ing current ; the resistance of the keeper to the rotation must also 

 increase at every step until it reaches a maximum, imposed by the 

 available force and the conductivity of the wires employed. 



The co-operation of the battery is only necessary for a moment 

 of time after the rotation has commenced, in order to introduce 

 the magnetic action, which will thereupon continue to accumulate 

 without its aid. 



With the rotation the current ceases ; and if, upon restarting 

 the machine, the battery is connected with the circuit for a 

 moment of time with its poles reversed, then the direction of the 

 continuous current produced by the machine will also be the re- 

 verse of what it was before. 



Instead of employing a battery to commence the accumulative 

 action of the machine, it suffices to touch the soft iron bars em- 

 ployed with a permanent magnet, or to dip the former into a 

 position parallel to the magnetic axis of the earth, in order to 



