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 lias, tp 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 armature 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. 
