ELECTRICITY. 99 



former class of phenomena. How the phenomena are pro- 

 duced to which the term attraction is applied is still a mys- 

 tery. Newton, speaking of it, says, 'What I call attraction 

 may be performed by impulse, or by some other means un- 

 known to me. I use that word here to signify only in gen- 

 eral any force by which bodies tend towards one another, 

 whatsoever be the cause.' If we suppose a fluid to act in at- 

 tractions and repulsions, the imponderable fluid must drag or 

 push the matter with it: thus when we feel a stream of 

 air rushing from an electrified metallic point, each molecule 

 of air contiguous to the point being repelled, another takes 

 its place, which is in its turn repelled : how does a hypo- 

 thetic fluid assist us here ? If we say the electrical fluid re- 

 pels itself, or the same electricity repels itself, we must go 

 farther and assert, that it not only repels itself, but either 

 communicates its repulsive force to the particles of the air, or 

 carries with it the particle of air in its passage. Is it not 

 more easy to assume that the particle of air is in such a state 

 that the ordinary forces which keep it in equilibrium are dis- 

 turbed by the electrical force, or force in a definite direction 

 communicated to it, and that thus each particle in turn re- 

 cedes from the point ? As this latter force is increased, not 

 only does the particle of air which was contiguous to the me- 

 tallic point recede, but the cohesion of the extreme particles 

 of metal may be overcome to such an extent that these are 

 detached, and the brush or spark may consist wholly or in 

 part of minute particles of the metal itself thrown off. Of 

 this there is some evidence, though the point can hardly be 

 considered as proved. A similar effect undoubtedly takes 

 place with voltaic electricity, acting upon a terminal im- 

 mersed in a liquid ; thus if metallic terminals of a powerful 

 voltaic battery be immersed in water, metal, or the oxide of 

 metal, is forcibly detached, producing great heat at the point 

 of disruption. 



If we apply ourselves to the effect of electricity in the 



