MAGNETO-ELECTRIC ILLUMINATION. 591 



reporter, Count du Moncel, a prize of 3,000 francs has been awarded 

 for it to M. Gramme ; while the manager of the " Alliance Company," 

 M. Joseph Van Malderen, who superintended its manufacture, has had 

 awarded to him a gold medal. In his report, Count du Moncel says 

 that a machine 1.25 metre in height, 0.8 metre long, and the same in 

 width, driven by a 4-horse engine, gave a light equal to 900 carcel- 

 lamps. It also heated to redness two juxtaposed copper wires 12 

 metres long and 0.7 m.m. diameter, and fused an iron wire 2.5 metres 

 lon and 1.3 m.m. thick. 



The constancy of direction of the electric current generated by 

 this machine is, however, not of so great an importance for the elec- 

 tric light as for other purposes for which it may be used. Indeed, the 

 electric light is by many electricians thought to be superior when pro- 

 duced by a magneto-electric machine of the old form without any 

 commutator. The alternate reversal of the currents of electricity pro- 

 duces no flickering or irregularity in the arc of light, as they occur far 

 too quickly to be appreciated by the eye, while the rapid reversal of 

 the direction causes the carbons to wear away with great regularity, 

 thus enabling the point of light to be kept more easily in the focus. 



For the electro-deposition of metals copper, silver, etc. constancy 

 of direction of current is indispensable, and here the experiments show 

 a marked superiority of the Gramme machine over other magneto- 

 electric machines. 



In the galvanoplastic works of M. Christofle, of Paris, where ex- 

 periments have been going on for more than a year, it is found that 

 the best machine hitherto known, when moved with a velocity of 2,400 

 revolutions per minute, only deposits 170 grammes of silver per hour; 

 while a smaller Gramme machine moved with a velocity of 300 revo- 

 lutions per minute deposits 200 grammes of silver per hour ; the tem- 

 perature of the annular armature not exceeding 50 C, with a velocity 

 of 275 revolutions, no elevation of temperature is experienced. It will 

 be easily comprehended how strongly this result, obtained with a speed 

 of rotation eight times less than hitherto required, speaks in favor of 

 M. Gramme's invention. Usually at M. Christofle's the circuits are 

 arranged to deposit 600 grammes of silver per hour, and the manager 

 of the factory finds that the deposition with this machine takes place 

 with a regularity and constancy which leaves nothing to be desired, 

 and which cannot be obtained by using any other source of electricity. 



Recently, the electric light generated by a Gramme machine has 

 been exhibited on the Victoria Tower of the Houses of Parliament. 

 The machine is placed in the vaults of the House of Commons, near to 

 the boilers, and is worked by a small engine, which was already there, 

 and was convenient for the purpose. From the machine two copper 

 wires, half an inch diameter, are led along the vaults to the base of 

 the clock-tower, and thence upward to the signalling-point, a total 

 length of nearly 900 feet, being about three times the distance that an 



