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 , resting on four feet, are placed the two similar electro-magnets ; each of them weighs about the 18th 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 . The board has in the middle a hole , cut in it where the poles lie; in this a frame 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 . Fixed in the side laths, and about 112 inch below it, is placed a stout iron wire parallel with the cylinder and passing through the sides of the frame, and two pieces of wood fixed in the under side of the board ; 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 may be placed on its base . The electric current was conveyed to the electro-magnets through a gyrotrope , standing on the board , which serves as a basis to the whole machine. The wires from the electromotors are connected with the two middle cups of mercury , in each of which dips the central portion of a wire bent into the form of an anchor . 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 , dip the wires from , coming from the one plate of the electromotor; and into the other cup , 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 , 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 difficulty 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 carrying a considerable weight for some time. The bad effects which this remaining magnetism would have on the motion of the armature between the two electro-magnets would undoubtedly be greatly counteracted by the magnets being placed with the dissimilar poles opposite to each other. In this form of arrangement it is evident that the magnet in action
