374 THE CONSERVATION OF FORCE. 



more complicated in their conditions. But still there is no 

 apparent desire to let loose the force of the principle of con 

 servation, even in those cases where the appearance and dis 

 appearance of force may seem most evident and striking. 

 Electricity appears when there is consumption of no other 

 force than that required for friction ; we do not know how, 

 but we search to know, not being willing to admit that the 

 electric force can arise out of nothing. The two electricities 

 are developed in equal proportions ; and having appeared, we 

 may dispose variously of the influence of one upon successive 

 portions of the other, causing many changes in relation, yet 

 never able to make the sum of the force of one kind in the 

 least degree exceed or come short of the sum of the other. 

 In that necessity of equality, we see another direct proof of 

 the conservation of force, in the midst of a thousand changes 

 that require to be developed in their principles before we 

 can consider this part of science as even moderately known 

 to us. 



One assumption with regard to electricity is, that there is 

 an electric fluid rendered evident by excitement in plus and 

 minus proportions. Another assumption is, that there are 

 two fluids of electricity, each particle of each repelling all 

 particles like itself, and attracting all particles of the other 

 kind always, and with a force proportionate to the inverse 

 square of the distance, being so far analogous to the defini 

 tion of gravity. This hypothesis is antagonistic to the law 

 of the conservation of force, and open to all the objections 

 that have been, or may be, made against the ordinary defini 

 tion of gravity. Another assumption is, that each particle of 

 the two electricities has a given amount of power, and can 

 only attract contrary particles with the sum of that amount, 

 acting upon each of two with only half the power it could in 

 like circumstances exert upon one. But various as are the 

 assumptions, the conservation of force (though wanting in the 

 second) is, I think, intended to be included in all. I might 



