24 ELEMENTS OF STATIC ELECTRICITY. 



it is evident that only a very small part of the mus- 

 cular energy expended would be required to move 

 the pith balls, the balanced rod, or the gold leaves, the 

 remainder must be accounted for. 



This is easily done when we consider, first, that 

 the electric energy was equally divided between the 

 rubber and the substance rubbed; secondly, that only 

 a small part of the electric energy was used ; that the 

 electricity generated was sufficient for the performance 

 of the same work many times in succession, cither 

 with the rubber or substance rubbed; and that a 

 number of pith balls, placed on all sides of the 

 electrified body, might have been subjected to its 

 influence. Thirdly, we must consider the amount of 

 electricity lost from contact with the surrounding air; 

 and, lastly, that the amount of heat energy gener- 

 ated by the friction was probably equal to the electric 

 energy. 



If the expended energy had been produced by a 

 descending weight, which should cause a glass or 

 ebonite cylinder to revolve in contact with a rubber, 

 and the sum total of the heat and electricity had 

 been recovered in the form of work which could be es- 

 timated, it would be found so nearly equal to the 

 number of foot-pounds expended by the descending 

 weight, that whatever difference existed could easily 

 be accounted for by the friction of the machinery and 

 other causes. 



Experiments of this kind have been actually per- 

 formed, and the results verify the above conclusion. 

 Similar experiments have also been made with other 

 forms of energy, and like results obtained ; so that 

 the principles of the conservation of energy are now 



