272 ELECTRICS. 



Electricity may be called into activity by mechanical 

 power, by chemical action, by heat, and by magnetic 

 influence. We are totally ignorant why it is roused 

 from its neutral state by such means, or of the manner 

 of its existence in bodies, whether it be a-material agent, 

 vibrations of ether, or merely a property of matter. 

 Various circumstances render it more than probable 

 that, like light and heat, it is a modification or vibration 

 of that subtile etlftreaT medium which in a highly elas- 

 tic state pervades all space, and which is capable of 

 moving with various degrees of facility through the pores 

 even of the densest substances. As experience shows 

 that bodies in one electric state attract, and in another 

 repel each other, the hypothesis of two fluids has been 

 adopted by many philosophers ; but probably the mutual 

 attraction and repulsion of bodies arise from the redun- 

 dancy and defect of their electricities, though all the 

 electrical phenomena can be explained on either hy- 

 pothesis. Bodies having a redundancy of the electric 

 fluid are said to be positively electric, and those in defect 

 negatively. As each kind of electricity has its peculiar 

 properties, the science may be divided into four branch- 

 es, of which the following notice is intended to convey 

 some idea. 



Substances in a neutral state neither attract nor 

 repel. There is a numerous class called electrics, 

 in which the electric equilibrium is destroyed by fric- 

 tion ; then the positive and negative electricities are 

 called into action or separated ; the positive is im- 

 pelled in one direction, and the negative in another ; 

 or more jflfcrectly, the electricity is impelled in one di- 

 rection, at^ie expense of the other where there is a de- 

 ficiency of it. .Electricities of the same kind repel, 

 whereas those of different kinds attract each other. 

 The attractive power is exactly equal to the repulsive 

 power at equal distances, and when not opposed, they 

 coalesce .with great rapidity and violence; producing 

 the electric flash, explosion, and shock : then equili- 

 brium is restored, and the electricity remains latent till 

 again called forth by a new exciting cause. One kind 

 of electricity cannot be evolved without the evolution of 

 an equal quantity of the opposite kind. Thus when u 



