of the Electrical Terms Intensity and Tension. 509 



of the external coating, and lessen its influence upon the inner 

 coating through the glass; eventually, therefore, as the accumu- 

 lation increases, the force between the coatings through the 

 glass is entirely superseded by the force between the coatings 

 through the external circuit. We see nothing in these simple 

 operations which would lead us to conclude that the increasing 

 divergence of the electroscope E is indicative of increasing elas- 

 ticity, tension, or other change of quality in the unknown agency. 



10. If, in accumulating a given quantity over three or more 

 equal electrical jars instead of one (as quoted by Riess), we find 

 the divergence of the electroscope greatly reduced, that is evi- 

 dently because there is less accumulation in any one point of the 

 charged surfaces, as we have already explained (5), and the elec- 

 troscope is consequently not affected to the same extent as it 

 would be if the accumulation were confined to one of the jars 

 only. 



We really cannot infer from these phenomena any change in 

 the quality of the electrical agency. It is true that the force of 

 the discharge will be something less when the accumulation is 

 on three jars instead of one jar; but that may be shown to arise 

 from the increased resistance to discharge, in consequence of the 

 greater, number of charging rods and wires the accumulation has 

 to traverse, and other circumstances attendant on the detached 

 surfaces. If the accumulation be confined to a large jar and a 

 small jar taken separately (in which the charging rod is the 

 same), the force of the accumulation would be pretty much 

 alike in each : for example, fifty measures accumulated on a jar 

 exposing 6 square feet of coating, produces nearly the same 

 heating effect upon a fine wire as fifty measures accumulated 

 and discharged from a jar of 3 feet or only half its surface, 

 although the relative electrometer intensities are nearly as 4 : 1 

 (supposing the thickness of the glass to be the same) ; the elec- 

 trometer indication is four times as great on the small jar. 



The force of the discharge, therefore, in this case bears no sort 

 of proportion whatever to the relative intensities, considered as 

 indicating any difference in the constitution of the accumulated 

 electricity. The force of the discharge is certainly something less 

 from the large jar, the amount of contact between the coatings 

 and the glass being much greater in the case of the large jar. 

 The accumulated electricity does not in fact escape so freely from 

 the charged side of the large jar as it does from the charged side 

 of the smaller jar; and hence a somewhat greater resistance to 

 discharge. A moment's reflection on the nature and construc- 

 tion of the electrical jar, and the relation subsisting between its 

 coatings, will be sufficient to further elucidate this important 

 fact. It is clear that the positive and negative coatings are 



