226 Apparent Conversion of Electricity into Mechanical Force. 



My object was to show, that when electricity performs any 

 mechanical work which does not return to its source, elec- 

 trical power is lost. The first experiment was made in the 

 following manner : — A Leyden jar of one square foot coated 

 svu'face has its interior connected with a Cuthbertson's electx'o- 

 meter, between which and the outer coating of the jar are a pair 

 of discharging balls fixed at a certain distance (about i an inch 

 apart). Between the Leyden jar and the prime conductor is 

 inserted a small unit-jar of 9 square inches surface, the knobs of 

 which are 0"2 inch apart. 



The balance of the electrometer is now fixed by a stifi^ wire 

 inserted between the attracting knobs, and the Leyden jar 

 charged by discharges from the unit-jar. After a certain num- 

 ber of these (twenty-two in the experiment performed in the 

 theatre of the Institution), the discharge of the large jar takes 

 place across the i-inch interval; this may be viewed as the 

 expression of electrical power received from the unit-jar. The 

 expei'iment is now repeated, the wire between the balls having 

 been removed, and therefore the ' tip' or the raising of the 

 weight is performed by the electrical repulsion and attraction 

 of the two pairs of balls ; at twenty-two discharges of the unit- 

 jar the balance is subverted, and one knob drops upon the 

 other, but no discharge takes place, showing that some electri- 

 city has been lost, or converted into the mechanical power which 

 raises the balance. By another mode of expression the elec- 

 tricity may be supposed to be masked or analogous to latent 

 heat, and would be restored if the ball were brought back, 

 without discharge, by extraneous force. 



The experiment is believed to be new, and to be suggestive of 

 others of a similar character, which may be indefinitely varied. 

 Thus, two balls made to diverge by electricity should not give 

 to an electrometer the same amount of electricity as if they 

 were, whilst electrified, kept forcibly together: an experiment of 

 this sort I have made since my lecture in the following manner. 

 To a thick brass wire, 2 feet long, insulated and terminated by 

 knobs, are suspended by fine platina wires, two pairs of discs of 

 paper coated with tinfoil, and 4 inches in diameter. The 

 apparatus is electrized in a dry atmosphere by sparks from a 

 machine, and the discs of each pair respectively diverge. To one 

 of the pairs a silk thread is attached, by which the discs can be 

 forcibly approximated, and as often as this is done, the diver- 

 gence of the other pair increases. 



Another mode of showing the same eff"ect is the following. 

 On the top of an ordinary gold-leaf electroscope place two brass 

 plates, such as those commonly used for a condenser, connect 

 them by a long fine wire, and electrify them by a rubbed rod of 



