436 FRAGMENTS OF SCIENCE. 



coupling of two Grammes, or of two Siemens together, 

 here effected for the first time, was followed by a very 

 great augmentation of the light, rising in the one case 

 from 6663 candles to 11,396, and in the other case from 

 6864 candles to 14,134. Where the arc is single and 

 the external resistance small, great advantages attach to 

 the Siemens light. After this contest, which was con- 

 ducted throughout in the most amicable manner, Sie- 

 mens 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 Em- 

 bankment and at the Holborn Viaduct, delivers four 

 currents, each passing through its own circuit. In each 

 circuit are five lamps through which the current be- 

 longing 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 voltaic battery so as to augment indefinitely its elec- 

 tro-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 



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

 been also chosen for India. 



