674 FRAGMENTS OF SCIENCE. 



throughout in the most amicable manner, Siemens ma- 

 chines of type No. 2 were chosen for the Lizard.* 



We have machines capable of sustaining a single light, 

 and also machines capable of sustaining several lights. 

 The Gramme machine, for example, which ignites the 

 Jablochkoff candles on the Thames Embankment and at 

 the Holboni Viaduct, delivers four currents, each passing 

 through its own circuit. In each circuit are five lamps 

 through which the current belonging to the circuit passes 

 in succession. The lights correspond to so many resisting 

 spaces, over which, as already explained, the current has 

 to leap; the force which accomplishes the leap being that 

 which produces the light. Whether the current is to be 

 competent to pass through five lamps in succession, or to 

 sustain only a single lamp, depends entirely upon the will 

 and skill of the maker of the machine. He has, to guide 

 him, definite laws laid down by Ohm half a century ago, by 

 which he must abide. 



Ohm has taught us how to arrange the elements of a vol- 

 taic battery so as to augment indefinitely its electro-motive 

 force that force, namely, which urges the current forward 

 and enables it to surmount external obstacles. We have 

 only to link the cells together so that the current generated 

 by each cell shall pass 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 annum re as, a 

 moment ago, we augmented the cells of our voltaic battery. 

 Each additional convolution, like each additional cell, adds 



* As the result of a recent trial by Mr. Schwendler, they have been 

 also chosen for India. 



