316 Magneto-Electric Illumination. [July, 



table, upon which again is a sliding platform, on which the 

 lamps themselves stand. There are two lamps, which are 

 in use alternately, the carbon points lasting but four hours, 

 while the House frequently sits for ten. 



The copper conductors terminate at the fixed part of the 

 machine, and the method of carrying the current from them 

 to the lamps is very ingenious, the moving parts of the 

 apparatus forming in themselves conductors. The negative 

 conductor is placed in metallic contact with one hinge of 

 the elevator table through the centre pin on which the table 

 revolves, and the positive conductor with the other hinge by 

 means of the brass roller path. The currents from those 

 points are conducted to the lamp table, and thence through 

 the traversing platform to the lamps, metallic contact being 

 obtained throughout the whole circuit by means of flat 

 springs moving over flat surfaces. The changing of the 

 lamps is effected, without any appreciable break of con- 

 tinuity in the light, by means of the traversing platform on 

 which they stand, and which has a sliding motion from side 

 to side. When the carbon points in one lamp are nearly 

 consumed, the traverser is quickly shifted from right to left, 

 or vice versa, as may be necessary. The break of contact is 

 but momentary, and only exists during the time required to 

 move the traverser rapidly through a space of six inches. 

 The light will not become extinct during that period, as 

 there is not sufficient time to allow the incandescence of 

 the carbon to entirely subside. The springs under the lamp 

 thrown out of use are by this action removed from the 

 metal plate in the lamp table, and the springs under the 

 fresh lamp are brought into contact, and the light is at once 

 produced anew. 



The intensifying apparatus at present in use is a holo- 

 phole lent by Messrs. Chance, and through which the rays 

 are sent in parallel lines. It is 21 inches in diameter, and 

 is composed of lenses, surrounded by annular prisms, the 

 centre part refracting the rays and the outer rings reflecting 

 them. Should the electric light be adopted, a special lens 

 will be constructed, by means of which the rays will be 

 diffused through an arc of 180°, instead of being sent in one 

 direction only. The cost of this electric light is at present 

 estimated at iod. per hour. 



It may be of interest if we consider some matters of scien- 

 tific interest in connection with this machine. In the first 

 place, it possesses an enormous advantage over the voltaic 

 battery in the absolute constancy of the current so long as the 

 velocity of rotation is uniform. In an experiment carried 



