1879.] on the Electric Light. 9 



fell short of tins definite amount, the missing heat being reproduced 

 to the last fraction in the glowing platinum wire and the other parts 

 of the machine. Here, then, the electric current intervenes between 

 my muscles and the generated heat, exactly as it did a moment ago 

 between the voltaic battery and its generated heat. The electric 

 current is to all intents and purposes a vehicle which transports the 

 heat both of muscle and battery to any distance from the hearth 

 where the fuel is consumed. Not only is the current a messenger, 

 but it is also an intensifier of magical power. The temperature of 

 my arm is, in round numbers, 100^ Fahr., and it is by the intensifi- 

 cation of this heat that one of the most refractory of metals, which 

 requires a heat of 3600^ Fahr. to fuse it, has been reduced to the 

 molten condition. 



Zinc, as I have said, is a fuel far too expensive to permit 

 of the electric light produced by its combustion being used for 

 the common purposes of life, and you will readily perceive in 

 reference to our last experiment that the human muscles, or even 

 the muscles of a horse, would be also very expensive. Here, 

 however, we can employ the force of burning coal to turn our 

 machine, and it is this emj)loyment of our cheapest fuel, rendered 

 possible by Faraday's discovery, which opens out to us the prospect of 

 being able to apply the electric light to public use. 



In 1866 a great stej) in the intensification of induced currents, 

 and the consequent augmentation of the magneto-electric light, was 

 taken by Mr. Henry Wilde. It fell to my lot to report uj)on them to 

 the Royal Society, but before doing so I took the trouble of going 

 to Manchester to witness Mr. Wilde's experiments. He operated in 

 this way, starting from a small machine like that worked in your 

 presence a moment ago, he employed its current to excite an electro- 

 magnet of a peculiar shape, between w^hose poles rotated a Siemens' 

 armature ; ^ from this armature currents were obtained vastly stronger 

 than those generated by the small magneto-electric machine. These 

 currents might have been immediately employed to produce the electric 

 light ; but instead of this they were conducted round a second electro- 

 magnet of vast size, between whose poles rotated a Siemens' armature 

 of corresponding dimensions. Three armatures therefore were 

 involved in this series of operations ; first, the armature of the 

 small magneto-electric machine ; secondly, the armature of the first 

 electro-magnet, which was of considerable size ; and thirdly, the 

 armature of the second electro-magnet, which was of vast dimensions. 

 With the currents drawn from this third armature Mr. Wilde ob- 

 tained effects, both as regards heat and light, enormously transcending 

 those previously known. | 



* Page and Moigno had previously shown that the magneto-electric current 

 could produce powerful electro-magnets. 



t Mr. Wilde's paper, comnmnicatod by Faraday, was received l)y the Royal 

 Society, IMarcli 2()th, and rea<l April 2Gtli, 18G6. It is piihlislicd in the ' Philoso- 

 phical Transactions' for 1SG7, p. 89. My opinion regarding Wilde's machine 



