THE ELECTRIC LIGHT. 439 



through all the others, and add its electro-motive force 

 to that of all the others. We increase, it is true, at the 

 same time the resistance of the battery, diminishing 

 thereby the quantity of the current from each cell, but 

 we augment the power of the integrated current to 

 overcome external hindrances. The resistance of the 

 battery itself may, indeed, be rendered so great, that 

 the external resistance shall vanish in comparison. 

 What is here said regarding the voltaic battery is 

 equally true of magneto-electric machines. If we wish 

 our current to leap over five intervals, and produce five 

 lights in succession, we must invoke a sufficient electro- 

 motive force. This is done through multiplying, by the 

 use of thin wires, the convolutions of the rotating arma- 

 ture as, a moment ago, we augmented the cells of our 

 voltaic battery. Each additional convolution, like each 

 additional cell, adds its electro-motive force to that of 

 all the others ; and though it also adds its resistance, 

 thereby diminishing the quantity of current contributed 

 by each convolution, the integrated current becomes 

 endowed with the power of leaping across the successive 

 spaces necessary for the production of a series of lights 

 in its course. The current is, as it were, rendered at 

 once thinner and more piercing by the simultaneous 

 addition of internal resistance and electro-motive power. 

 The machines, on the other hand, which produce only a 

 single light have a small internal resistance associated 

 with a small electro-motive force. In such machines the 

 wire of the rotating armature is comparatively short and 

 thick, copper riband instead of wire being commonly 

 employed. Such machines deliver a large quantity of 

 electricity of low tension in other words, of low leaping 

 power. Hence, though competent when their power is 

 converged upon a single interval, to produce one 

 splendid light, their currents are unable to force a 



