LADD AND LONTIN. 275 



pass to work the larger and lower electro-magnet, which is composed of two 

 large sheets of iron connected by a plate (on which stands the exciter). Its 

 poles are two masses of iron separated by a layer of copper, and in this 

 armature revolves the larger longitudinal bobbin. This lower machine is 

 called the generator. Both bobbins are simultaneously revolved, and an 

 intense current of electricity is thereby generated. Almost simultaneously 

 with this one Mr. Ladd invented his machine, which is distinguished from all 

 hitherto described by being composed of two parallel bar electro-magnets, 

 between the extremities of which are placed two Siemens armatures, one 

 smaller than the other ; both being revolved, the smaller excites the electro- 

 magnets, and the larger generates the electricity required. The wire is 

 wound round the magnets so that the N. and S. poles face each other at 

 each end. The chief advantage of the Ladd machine is the conversion of 

 dynamic force into electricity, there always being just sufficient magnetism 



Fig. 275. The Wallace Machine. 



in an iron bar (by induction from terrestrial magnetism and other causes) to 

 produce a very feeble current in the Siemens bobbin, and the bobbin taking 

 it up and returning it to the electro-magnet, and the electro-magnet at once 

 giving it back to the bobbin, the current gradually increases till the maximum 

 is reached. And when we take into consideration this modicum of utilisable 

 terrestrial magnetism, we may truly say in the words of M. Hippolyte 

 Fontaine, " The mind is lost in contemplation of the succession of discoveries 

 completing one another, and showing that with apparatus of small dimensions 

 an infinite source of electricity could be produced if matter could withstand 

 infinite velocities." The Lontin machine, which supplied the current for the 

 electric light which used to make night bright outside the Gaiety, is also 

 composed of two parts, one dividing, the other generating the electricity 

 produced. The principle of the dividing machine is somewhat similar to 

 the alliance, excepting that a number of electro-magnets arranged radially 

 round a core, revolve close to a corresponding number of bobbins fixed 

 inside an iron cylinder, outside which is the collecting and dividing apparatus. 



