64 ELECTRICITY. 



by the lines must, from the hypothesis, 

 be regarded as equal in point of in- 

 tensity : but the number of repulsive 

 forces is as -five, while that of the at- 

 tractive forces is only as four: the 

 former therefore will prevail. 



(237.) Precisely the same result will 

 obtain in the case of two negatively 

 electrified bodies, in which, as repre- 

 sented in fig. 47, the quantity of matter 



Fig. 47. 



is twice as much as the fluid can satu- 

 rate. In the former case it was the 

 repulsion between the two portions of 

 fluid which were in excess that de- 

 stroyed the equilibrium ; while in this 

 case the same effect is produced by the 

 mutual repulsion of the unsaturated 

 portions of matter. 



(238.) Lastly, we may collect from 

 an examination of fig. 48, where a body 



Fig. 48. 



.positively electrified is supposed to be 

 placed near one that is negatively elec- 

 trified, that the ultimate effect will be 

 determined by the attraction between 

 the fluid in excess in the former, and 

 the unsaturated matter in the latter : 



all the other attractions and repulsions 

 exactly compensating each other. 



(239.) It is a great, though a com- 

 mon error to imagine, that the condition 

 assumed by ^Epinus, namely, that the 

 particles of matter, when devoid of 

 electricity, repel one another, is in op- 

 position to the law of universal gravi- 

 tation established by the researches of 

 Newton ; for this law applies, in every 

 instance to which inquiry has extended, 

 to matter in its ordinary state, that is, 

 combined with a certain proportion of 

 electric fluid. By supposing, indeed, 

 that the mutual repulsive action be- 

 tween the particles of matter is, by a 

 very small quantity, less than that 

 between the particles of the electric 

 fluid, a small balance would be left in 

 favour of the attraction of neutral 

 bodies for one another, which might 

 constitute the very force which operates 

 under the name of gravitation: and 

 thus both classes of phenomena may 

 be included in the same law. 



(240.) An objection has been urged 

 by Biot against the hypothesis of a 

 single, fluid, on the ground that it im- 

 plies an equal degree of attraction be- 

 tween the fluid and every species of 

 matter, whereas in the case of other 

 agents, such as heat and magnetism, 

 the degree of their attraction is very 

 different towards different kinds of 

 matter. This objection does not apply 

 to the hypothesis of the two fluids, for 

 they are assumed as acting independ- 

 ently of any specific attractions for the 

 bodies which contain them : hence their 

 distribution in those bodies follows the 

 same law, whatever be the specific 

 nature of the materials of which the 

 latter are composed. 



(241 .) We arrive, then, at the conclu- 

 sion that there is no fact in electricity 

 which cannot be explained on either of 

 the two hypotheses : but to which side 

 the balance of probabilities may incline, 

 when the respective merits and demerits 

 of each are taken into account, remains, 

 perhaps, to be decided more by the 

 taste than the judgment of the inquirer. 



ERRATA IN PART 



Page. Col. Line. 



6, 1, 



7, 1, 

 9, 1, 



ib. 



3, from bottom, omit the line "Ice 



above 13 Fahrenheit." 

 10. omit*" of six inches, that is." 

 36, for " resinous," read " vitreous." 



1. 37, for " vitreous," read " resinous. 



Page. Col. Line. 



20, 1, I, for " silken," read " silk." 

 2'2, 1, 10, for " spheroid^," read " spheroid." 

 ib. 2, 10, from bottom, fur "smaller," read 

 " greater." 



