668 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK v. 



weight of silver deposited per hour to 2,100 grammes, or above 4. 1 , 

 Ibs. In Figs. 437 and 438 we have the forms of the Gramme machine 

 now in use for the production of the electric light. They are im- 

 provements on the machine which was tried on the Clock Tower of 

 Westminster Palace. It produces a normal light of 500 Carcel 

 burners ; but, by augmenting the velocity, it is asserted that the 

 amount of light may be doubled. It does not become heated, nor 

 does it produce any spark where the brushes are applied. 



In Fig. 438 we have the latest improvements devised by M. Gramme 

 for producing the electric light. In this machine there are only two 

 bar electro-magnets arid a single movable ring placed between the 

 electro-magnets. Its weight is 183 kilogrammes, and the entire 

 weight of copper used in its construction, both for the ring and for 

 the electro-magnets, amounts to forty-seven kilogrammes. Its normal 

 power is about 200 Carcel burners, but this can be greatly augmented 

 by increasing the velocity. 



By uniting two or more machines together, electrical currents of 

 high tension may be obtained, But a more useful arrangement is to 

 divide into two each ring, so that the two halves may be joined either 

 for quantity or tension, and varied effects thus obtained from the same 

 machine. This is effected in the following manner. Suppose the 

 machine to contain sixty bobbins or helices round the ring, If the 

 entrance of the thirty alternate bobbins is placed on one side of the 

 ring and of the thirty other bobbins on the other side, there will be 

 in reality two ring-arm atures in one, interlaced as it were into each 

 other; and by collecting the currents by means of two. systems of 

 rubbers, one to the right and the other to the left of the ring, we may 

 obtain from each one half of the electricity produced by the rotation 

 of the ring. By applying this principle to machines for producing the 

 electric light, the same machine may give two distinct lights instead 

 of one. In its industrial applications, this is a point of capital im- 

 portance. The use of the electric light is at present greatly interfered 

 with by its excessive brightness, and the deep shadows which by 

 contrast are produced at the same time. These defects will be to 

 a large extent remedied by the use of two lights, so that the shadow 

 from one may be illuminated by the other. It is proposed to use four 

 .electric lights, each of the strength of fifty Carcel burners, for lighting 

 foundries and large workshops. 



