I 



ELECTRO-MAGNETISM AS A MECHANICAL POWER. 539 



previously commenced. I hastened the completion of the apparatus so 

 that I was enabled to exhibit it before the Mechanics' Society on the 

 18th of January. The construction of it is as follows (Plate VII.) : 



On a small board A' A', resting on four feet, are placed the two si- 

 milar electro-magnets GG' ; each of them weighs about the |th part of 

 a pound, and is wound round with 80 convolutions of copper wire of 

 0*5 line in diameter, covered with silk : they can be made to recede 

 from or approach each other, and are fixed in their places by wooden 

 screws J J'. The board has in the middle a hole B B, cut in it where 

 the poles lie; in this a frame EE is hung, made out of four laths joined 

 together, forming an oblong, of which the long sides are vertical. Under 

 the upper side, and parallel with it, is the iron cylinder or armature K K'. 

 Fixed in the side laths, and about 1^ inch below it, is placed a stout 

 iron wire F parallel with the cylinder and passing through the sides 

 of the frame, and two pieces of wood C C fixed in the under side of 

 the board A'A' ; this wire serves as an axis, which allows to the frame 

 a pendulum-like motion. That part of the frame which is below the 

 axis is twice as long as the upper part, and weights O O may be placed 

 on its base E" E". The electric current was conveyed to the elec- 

 tro-magnets through a gyrotrope P P, standing on the board A A, 

 which serves as a basis to the whole machine. The wires from the elec- 

 tromotors are connected with the two middle cups of mercury dd', in 

 each of which dips the central portion of a wire bent into the form of 

 an anchor QQ. These two wires are fixed to a wooden bow, by the 

 motion of which the alternate ends of the two bent wires dip either into 

 the cups on the one side or into those on the other ; into the one cup 

 d, dip the wires fromy^ coming from the one plate of the electromotor; 

 and into the other cup d', those from the other plate. The motion of 

 this bow is effected in a very simple way by means of the motion of 

 the frame E E' E", so that when the iron cylinder is attracted by the 

 electro-magnet on the right hand, the bow of the gyrotrope is driven 

 by the lower part of the frame to the left hand, by which motion the 

 left-hand electro-magnet is brought into action. The working of this 

 little self-acting apparatus is so quick and efficient, that another small 

 machine, for instance, a wheel, might very easily be set in motion by 

 it. Before the result was quite successful, there was still another dif- 

 ficulty to be overcome. It is a well-known fact that electro-magnets, 

 when the connexion of the wires with the electromotors is interrupted, 

 do not instantly lose all their magnetism, but are capable of carrj'ing a 

 considerable weight for some time. The bad effects which this remain- 

 ing magnetism would have on the motion of the armature between tlie 

 two electro-magnets would undoubtedly be greatly counteracted by the 

 magnets being ])laced witli the dissimilar poles opposite to each other. 

 In this form of arrangement it is evident that the magnet in action 



