400 EXPERIMENTAL INVESTIGATIONS. 



The number of discharges in a given time will depend upon 

 the intensity of the battery, and its relation to the amount 

 of coated surface ; the eye cannot estimate this, but a rough 

 measurement of the rapidity of succession may be made in 

 the following way : Move across the line of discharge with a 

 steady hand a strip of writing-paper : it will be punctured with 

 a row of holes, which will be the more closely approximated 

 in proportion as the succession of discharges is more rapid. 

 By a disc of paper attached to an axis moving with a given 

 rate of revolution this measurement may be made very accu- 

 rate and useful. 



Those who possess the coil apparatus will find it very con- 

 venient to have a plate of glass, coated on each side with tin- 

 foil, placed in the base of the machine, and having strips 

 leading from each coating to binding-screws, with which the 

 terminals of the secondary coil can be connected at will. 



EXPERIMENTS ON THE APPARENT CONVERSION OF 

 ELECTRICITY INTO MECHANICAL FORCE. 



Phil. Mag., January 1856. 



IN a communication made to the members of the Royal 

 Institution, on Friday, January 25, entitled ' Inferences from 

 the Negation of Perpetual Motion,' I showed an experiment 

 which, with one or two others now added, may be thought 

 worth recording in the * Philosophical Magazine.' They are 

 hardly, I think, likely to be deduced from our received elec- 

 trical theories, though possibly not inconsistent with some of 

 them. 



My object was to show that when electricity performs any 

 mechanical work which does not return to its source, electrical 

 power is lost, The first experiment was made in the following 

 manner : A Leyden jar of one square foot coated surface has 

 its interior connected with a Cuthbertson's electrometer, be- 

 tween which and the outer coating of the jar are a pair of dis- 

 charging balls fixed at a certain distance (about -J an inch 

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



