Discussion of the results as to law of force 123 



of the globe was not sufficient to make the balls separate, unless they were 

 previously electrified. 



It is plain that the quantity of redundant fluid communicated to the 

 globe in this experiment was less than ^th part of that communicated to the 

 hemispheres in the former experiment, for if the hemispheres themselves had 

 been electrified they would have received only ^th of the redundant fluid 

 they did before, and the globe, as being less, received still less electricity. 



231] It appears, therefore, that if a globe 12-1 inches in diameter is 

 inclosed within a hollow globe 13-3 inches in diameter, and communicates 

 with it by some conducting substance, and the whole is positively elec- 

 trified, the quantity of redundant fluid lodged in the inner globe is certainly 

 less than g'^th of that lodged in the outer globe, and that there is no reason 

 to think from any circumstance of the experiment that the inner globe is 

 at all overcharged. 



232] Hence it follows that the electric attraction and repulsion must 

 be inversely as the square of the distance, and that when a globe is posi- 

 tively electrified, the redundant fluid in it is lodged intirely on its surface. 



For by Prop. V [Art. 20], if it is according to this law, the whole 

 redundant fluid ought to be lodged on the outer surface of the hemispheres, 

 and the inner globe ought not to be at all over or undercharged, whereas, 

 if it is inversely as some higher power of the distance than the square, 

 the inner globe ought to be in some degree overcharged. 



233] For let ADB (Fig. 13) be the hemispheres and adb the inner globe, 

 and Aa the wire by which a com- 

 munication is made between them. 

 By Lemma IV [Art. 18], if the elec- 

 tric attraction and repulsion is in- 

 versely as some higher power of the 

 distance than the square, the re- 

 dundant fluid in ABD repels a 

 particle of fluid placed anywhere in 

 the wire A a towards the center, and 

 consequently, unless the inner globe 

 was sufficiently overcharged to pre- 

 vent it, some fluid would flow from 

 the hemispheres to the globe. 



But if the electric attraction and 

 repulsion is inversely as some lower power of the distance than the square, 

 the redundant fluid in ABD impels the particle in the contrary direction, 

 that is, from the center, and therefore the inner globe must be undercharged. 



234] In order to form some estimate how much the law of the electric 

 attraction and repulsion may differ from that of the inverse duplicate 



Fig. 13- 



