92 ELECTRIC LIGHTING. 



scale of Wilde's machine, already spoken of, and of Lontin's 

 machine, which is based on the same principle. 



It consists of a large iron disc, provided on both sides with 

 crowns of straight electro-magnets, and turning between the 

 poles of two large electro-magnets with flat branches, having 

 the contrary poles opposite each othen The somewhat 

 flattened coils are connected together for tension on each 

 side of the revolving disc, and the connecting wires are in 

 communication with a collector placed on the axle of rota- 

 tion, as in the Gramme system, so as to avoid a reversing 



commutator. This ar- 

 rangement, in which 

 there is absolutely no 

 novelty, is shown in Fig. 

 28. 



It will be perceived 

 that by this arrangement 

 the machine is double, 

 and that each of its 

 parts might act indepen- 

 FIG. 28. dently; but practically 



the electrical communi- 

 cations are so contrived that the currents evolved are united 

 either for quantity or for tension through the whole circuit. 

 The inventor believes that heating effects are avoided by the 

 large uncovered surface presented by the revolving disc; 

 but the Committee pointed out that this advantage is pur- 

 chased at the expense of the great resistance which the air 

 offers to the motion of the machine ; and further, it may be 

 seen by the experiments performed before the Committee 

 that the machine was heated sufficiently to melt sealing-wax. 



Brush's machine. Brush's machine, represented in 

 Fig. 29, is one of those experimented with by the Committee 

 of the Franklin Institute, and it was, in fact, the one to which 

 the palm of superiority was awarded. Jn its principle this 



