i873-] Magneto-Electric Illumination. 311 



and there is no circulation. The result may be likened 

 to what would be produced by taking two batteries, each 

 of 20 cells, and connecting them in opposition by joining 

 similar poles. 



The problem now is to pick up these dormant currents 

 and utilise their force. Its solution is apparent from the 

 comparison we have just made. To collect the electric 

 current from two batteries which are connected together in 

 opposition, it is only necessary to fasten conducting wires 

 to the two points of contact of similar poles, when the whole 

 force of the batteries will flow along these wires. They 

 were hitherto opposed, they now flow together, quantity- 

 wise. M. Gramme, in the second portion of his invention, 

 has adopted this artifice in an ingenious manner. 



The various sections of the continuous electro-magnet are 

 connected with radial pieces of copper shown at R in Figs. 

 3, 4, and 7, insulated one from the other, but coming very 

 close. The termination of one coil of wire and the com- 

 mencement of the adjacent coil are soldered to the same 

 radial connector, of which therefore there are as many as 

 there are coils. These radial connectors, on approaching 

 the centre, are bent at right angles, as shown at R, Figs. 4 

 and 7, and pass through to the other side, where their ends 

 form an inner concentric circle, being still insulated one 

 from the other. 



Two friction pieces F (Figs 4, 5, and 6) consisting of 

 discs of copper, are pressed by means of springs shown 

 at y (Figs. 5 and 6) against the circle formed by the 

 extremities of the conducting radii r, at two points which 

 are accurately in the equatorial line; that is to say, at the 

 place where the equal and opposed currents generated in 

 the upper and lower halves of the ring neutralise each 

 other. Consequently the currents are collected and flow 

 together along conducting wires, which are fastened to the 

 friction pieces F. 



The perfect continuity of the current so obtained, is 

 secured by causing the friction pieces F to touch simul- 

 taneously several of the radial conductors R ; consequently 

 the metallic circuit is never broken. 



The effects produced by these machines vary with the 

 rapidity of rotation. Experience shows that the electro- 

 motive force is sensibly in proportion to the velocity ; but it 

 is probable that this force tends towards a limit, correspond- 

 ing to a particular velocity, beyond which the electromotive 

 force would remain constant, or even diminish. Moreover, 

 the electromotive force is greater in proportion to the 



