CHAP. VIL] MAGNETO-ELECTRIC MACHINES. 



661 



magnet could be explained on the hypothesis of electrical currents in 

 a fixed direction circulating around the magnet. A problem which 

 proved to be one of surpassing difficulty, and long baffled many of the 

 most distinguished physicists of Europe to obtain electrical currents 

 by means of a steel magnet was in 1831* completely solved in the 

 exhaustive memoir by Faraday, in which he announced 'the discovery 

 of the induction of electrical currents. 



Soon after the announcement of these important results, Pixii 

 constructed in Paris the first magneto-electric machine. The currents 

 were obtained by the rotation of a powerful horse-shoe magnet in front 



FIG. 431. - raciuotti's mac 



of an armature composed of two short bars of soft iron with a connect- 

 ing crossbar, the latter being surrounded by a long coil of copper wire 

 covered with silk. The armature had, in short, nearly the form of a 

 horse-shoe electro-magnet. With this machine electrical sparks were 

 obtained, and water was freely decomposed. In the rotation of the 

 magnet the faces of the armature or electro-magnet became successively 

 north and south poles with intermediate conditions of neutrality, and 

 the direction of the current changed at every semi-revolution of the 

 magnet. An important modification of Pixii's machine was soon after 

 made by Saxton, who caused the armature to revolve instead of the 

 permanent magnet. 



