CONSTANT CHARACTER OF THE CURRENT. 159 



much more likely to attain the real truth, and from that proceed with safety to what 

 is at present unknown ? 



1629. I say these things not, I liope, to advance a particular view, but to draw the 

 strict attention of those who are able to investigate and judge of the matter, to what 

 must be a turning point in the theory of electricity ; to a separation of two roads, ©ne 

 only of which can be right : and I hope I may be allowed to go a little further into 

 the facts which have driven me to the view I have just given. 



1630. When a wire in the voltaic circuit is heated, the temperature frequently 

 rises first, or most at one end. If this effect were due to any relation of positive or 

 negative as respects the current, it would be exceedingly important. I therefore ex- 

 amined several such cases; but when, keeping the contacts of the wire and its position 

 to neighbouring things unchanged, I altered the direction of the current, I found 

 that the effect remained unaltered, showing that it depended, not upon the direction 

 of the current, but on other circumstances. So there is here no evidence of a dif- 

 ference between one part of the circuit and another. 



1631. The same point, i. e. uniformity in every part, may be illustrated by what 

 may be considered as the inexhaustible nature of the current when producing par- 

 ticular effects ; for these effects depend upon transfer only, and do not consume the 

 power. Thus a current which will heat one inch of platina wire will heat a hundred 

 inches (853. note). If a current be sustained in a constant state, it will decompose 

 the fluid in one voltameter only, or in twenty others if they be placed in the circuit, 

 in each to an amount equal to that in the single one. 



1632. Again, in cases of disruptive discharge, as in the spark, there is frequently 

 a dark part (1422.), which, by Professor Johnson, has been called the neutral point*; 

 and this has given rise to the use of expressions implying that there are two electri- 

 cities existing separately, which, passing to that spot, there combine and neutralize 

 each other-f-. But if such expressions are understood as correctly indicating that 

 positive electricity alone is moving between the positive ball and that spot, and ne- 

 gative electricity only between the negative ball and that spot, then what strange 

 conditions these parts must be in ; conditions, which to my mind are every way un- 

 like that which really occurs ! In such a case, one part of a current would consist of 

 positive electricity only, and that moving in one direction ; another part would con- 

 sist of negative electricity only, and that moving in the other direction ; and a third 

 part would consist of an accumulation of the two electricities, not moving in either 

 direction, but mixing up together, and being in a relation to each other utterly unlike 

 any relation which could be supposed to exist in the two former portions of the dis- 

 charge. This does not seem to me to be natural. In a current, whatever form the 

 discharge may take, or whatever part of the circuit or current is referred to, as much 

 positive force as is there exerted in one direction, so much negative force is there 

 exerted in the other. If it were not so we should have bodies electrified not merely 



* Silliman's Journal, 1834, xxv. p. 57. f Thomson on Heat and Electricity, p. 471. 



