i873-] Magneto-Electric Illumination. 315 



170 grammes of silver per hour ; whilst a smaller Gramme 

 machine moved with a velocity of 300 revolutions 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 favour 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 upwards 

 to the signalling point, a total length of nearly 900 feet, 

 being about three times the distance that an electric 

 current has ever before been conducted for a similar 

 purpose. The signalling apparatus is placed in a lantern 

 5 feet high, 4 feet wide, and having a semi-circular glazed 

 front, which projects from the lantern of the belfry on the 

 north side of the tower, or that overlooking the Victoria 

 Embankment. It consists — first, of a fixed table, in which 

 is inserted a flat brass ring 16 inches diameter and 1 inch 

 broad, which serves as a roller path for the apparatus 

 carrying the lamp and reflector ; next, there is a circular 

 revolving table, having bearings on the roller path, and 

 which is moved around a central pivot projecting from the 

 fixed table, being actuated by a worm wheel and screw. 

 By means of this arrangement the light can be directed 

 horizontally from side to side through an arc of 180 . It 

 could, of course, be made to sweep the whole of the horizon, 

 but the position of the lantern with regard to the clock 

 tower is such as to enable the light to be seen through the 

 range of a semi-circle only. Upon the revolving table, and 

 hinged to it at the front is the elevating table, which has a 

 screw adjustment to the rear by which the light can be 

 raised or depressed, being capable of vertical training 

 through an arc of 25°. On the elevator is placed the lamp 



