-1859] 



WRITINGS OF JOSEPH HENRY. 



315 



In the first place, if the setherial medium in its ordinary- 

 state of diflfusion fills all space, then it must be evident that 

 when a body is charged with more than its natural share, 

 a portion must be drawn from space around, and hence 

 what one body gains other bodies in the vicinity must lose, 

 or in other words there must always be as much negative 

 excitement as positive. To exhibit this, as well as to illus- 

 trate some of the effects of the disturbance of the electrical 

 equilibrium, provide two strips of glass an inch in width and 

 twelve inches long, and on the end of one of these fasten with 

 beeswax or sealing-wax a piece of woollen cloth about an inch 



and a half long; if the glass 

 slips are warmed and rubbed 

 together, as shown in Figure 

 1, and afterwards separated, 

 they will exhibit signs of elec- 

 tricity. If the strip of glass of 

 which the end is naked be 

 brought near a pith-ball C, sus- 

 pended by a single fibre of non- 

 conducting silk, so that the 

 electricity which may be com- 

 municated to the ball cannot 

 escape, the ball will be attracted, 

 and immediately afterwards re- 

 pelled. If now the end of the 

 other glass having the woollen 

 cloth on it be brought near to 

 the same ball, attraction will 

 take place at a considerable dis- 

 tance. The one slip of glass will constantly attract, while 

 the other will as constantly repel the ball. If however the 

 two glasses be placed in contact as they were when first 

 rubbed, and thus presented to the ball, neither attraction 

 nor repulsion will be exhibited. 



These results are in strict accordance with the theory we 

 have adopted. By rubbing the glass and woollen cloth 

 against each other the electrical equilibrium is disturbed — 



Fig. 1. 



