206 



ELECTRIC LIGHT 



be maintained in activity for hours and probably the batttery was charged anew 

 every^eyening. There can be no doubt but the cost of light or of any other force from 

 electricity, with our present means of producing it, must be greatly in excess of any 

 of our ordinary means of producing illumination. For a consideration of this subject, 

 see ELECTRO-MOTIVE ENOINKS. Mr. Grove proposed a light which should be obtained 

 from incandescent platinum, but the objection to this was, that after a short period, 

 the platinum broke up into small particles, the electric current entirely disintegrating 

 the metal. Mr. Way exhibited a very continuous electric light, produced from a con- 

 stant flow of mercury rendered incandescent by the passage of the electric current. 

 The light obtained by the action of a magneto-electric engine, especially in the form 

 employed by Mr. Holmes, is not by any means so expensive as the electric light ob- 

 tained from the voltaic battery. After the first cost of the machine, the only cost of 

 importance is the mechanical power produced by a small steam-engine. The following 

 is perhaps the most important advance which has been made in the direction of the 

 useful application of electrical power. 



Wilde's Magneto-Electric Machine. The principle of this apparatus, which 

 has been invented by Mr. Wilde of Manchester, for the purpose of obtaining the 

 electric light more promptly and of higher density than had hitherto been done, 

 consists in directing a current of electricity from an electro-magnetic machine armed 

 with permanent magnets, so as to excite a still more powerful electro-magnet. This 

 electro-magnet is again used by Mr. Wilde as the basis of a still larger electro-magnetic 

 machine, in which induction currents are generated by its agency. The electric current 

 is obtained by the well-known means of causing the rotation of an armature close to 

 the poles of a permanent magnet, this electric current being made to pass round an elec- 

 tro-magnet, which causes it to produce a far greater amount of magnetism than was 

 possessed by the first magnet. If, again, the amount of magnetism thus obtained is 

 passed round a still larger electro-magnet, we should produce a vastly greater develop- 

 ment of electric force ; therefore, by the application of sufficient power to rotate the 

 several armatures, there seems to be no limit to this multiplication offeree, excepting 

 the excessive heat developed by the rotation of the armatures and the intensity of the 

 light produced. The construction of this machine will be more readily understood by 

 the annexed diagram (fig. 791 ), representing an end view. 

 At a are sixteen permanent horse-shoe magnets, which 

 are bolted on to a hollow magnetic cylinder, b c b, 

 composed of brass and iron, and so arranged that the 

 iron portions of it, b b, are screwed on to the respective 

 poles of the magnets at d, separated from each other by 

 the brass pieces c, and forming one entire north pole 

 and one entire south pole to the sixteen magnets. The 

 armature n, which is made to revolve in close proximity 

 to the interior of this cylinder, in suitable bearings at 

 the extremities, consists of a cylinder of cast iron on 

 which is wound, in direction of its length, about fifty feet 

 of insulated copper wire one-eighth of an inch in dia- 

 meter, and is bound round with brass rings, in order 

 that the centrifugal force caused by the rapid rotation 

 may prevent the wires from flying out of position ; the 

 inner extremity of this wire is fixed in good metallic 

 contact with the armature, the other end being con- 

 nected with the insulated half of a commutator which 

 is placed on one end of the armature. The armature 

 is made to revolve at the rate of 2,500 revolutions per 

 minute, by a driving band working on a pulley attached 

 to the other end of the armature. During each re- 

 volution of this armature two waves of electricity, mov- 

 ing in opposite directions, are induced in the insulated 

 copper-wire surrounding the armature ; the rapid suc- 

 cession of the alternating waves thus generated at the 

 rate of 5.000 per minuto, are converted by moans of the commutator into an inter- 

 mittent current moving in one direction only, which is conducted along the wires. 



The electro-magnetic machine by which the light is produced is of precisely tho 

 same construction as the magneto-electric machine above described, except that instead 

 of the permanent magnets a, an electro-magnet i is substituted ; this electro-magnet is 

 formed of two rectangular plates of rolled iron, 36 in. in length, 26 in. in width, and 

 1 in. in thickness ; they are bolted parallel to each other, to the magnetic cylinder 

 j\ which is similar in construction but of larger dimensions to that described above. 

 'These plates are connected together at their upper extremities by a cross piece formed 

 of two thicknesses of the same iron ; around the sides of this electro-magnet is coilod 



