conductor A, similarly situated, was presented to the ball on the negative side of the machine. The whole apparatus was supported upon glass pillars and had no electrical communication with the ground by means of a chain or otherwise. Upon turning the glass cylinder of the machine, a constant succession of sparks took place between the ball of the prime conductor of the machine and the ball of the insulated conductor B, as also a constant succession of sparks took place between the ball at the negative side of the machine and the ball of the insulated conductor A, and by continuing to work the machine a rapid succession of sparks for any length of time was maintained. 39. But in this last experiment, it is said that the metallic points which project from the conductors A and B withdraw electricity from the atmosphere which is imparted to the machine, and this is indicated by a constant succession of sparks that takes place between the balls of the conductors A and B, and those of the machine itself. That this view is also erroneous. I removed from their place the conductors with the metallic points, and into the upper part of each of the conductors of the machine I inserted the extremity of a brass wire, the other extremity of which terminated in a brass ball; the wires with the balls were made to bend towards each other as is represented in Fig. 6. I found by this addition to the electrical machine, that upon turning the glass cylinder a constant succession of sparks took place between the balls. As the common electrical machine has all its projections rounded off, it does not, when insulated, give off with facility electricity to the atmosphere, or to the surrounding bodies, or withdraw electricity from them. This constant succession of sparks between the balls, must therefore be derived from the machine itself. In order to prove that the electricity thus made manifest was not derived from the atmosphere, I replaced the conductors with the metallic points in their former position, connecting, however, the balls at their extremities with the balls of the conductors of the machine. Upon again turning the glass cylinder, the electric sparks between the balls (Fig. 6) did not now take place. It was therefore obvious that the metallic points of the insulated conductors, instead of supplying additional electricity to the machine by withdrawing it from the atmosphere, withdrew electricity from the machine, and gave it off to the atmosphere; and in a dark room this was indicated by the appearance of minute sparks of electricity at the metallic points of the conductors. 40. If heat is a binary compound, of which the elements are the two electricities, is it by the decom position of heat that electricity by induction is evolved? When a body is charged with one of the two electricities, electrical induction takes place in the body to which it is presented-is the heat of the induced body decomposed, one of the constituents of which is attracted, and the other repelled, by the adjacent body charged with one of the two electricities? I may state one or two examples of electrical induction as, I conceive, they occur in nature. When a cloud charged with one of the two electricities passes over the spire of a church, the spire by electrical induction is charged with the opposite electricity; and when the attraction of the two electricities, that of the cloud and that of the spire, is such as shall overcome the low conducting power of the atmosphere, the electricity of the cloud descends and unites with the electricity of the spire, and thus, in common parlance, the spire is said to be struck with lightning. Again, when a cloud charged with one of the two electricities passes over the surface of the ocean, it induces the opposite electricity in the water beneath; and because of the attraction of the two electricities, that of the cloud and that of the water beneath, the D |