3C6 Mr. J. Croll on Ampere's Experiment on the Repulsion 



parts, and repel the horizontal part D D. If Prof, van Breda 

 were to cut his conductor asunder at the points where they in- 

 tersect the currents in the mercury, and by some contrivance or 

 other still allow the current to pass, he would find that the hori- 

 zontal part would be instantly repelled, and the perpendicular 

 parts instantly attracted ; but when the whole is in one rigid 

 piece, as in his apparatus, no motion can possibly take place. 



Granting that the conductor is moved by the repulsion of the 

 current on itself, still it certainly must be admitted that Am- 

 pere's experiment cannot prove the fact; for if we admit, in 

 regard to his experiment, that the same motion under exactly 

 the same conditions ought to take place from the influence of 

 angular currents, then, when the motion does take place, we have 

 no warrant to conclude that it is not due to angular currents, 

 but to some other cause. The inference is the same whether 

 the conductor be composed of solid copper or of fluid mercury ; 

 for the motion does not depend upon the nature of the conductor, 

 but simply upon its position in relation to the impelling current. 



If we reverse the direction of the points of the conductor, as 

 Prof, van Breda has ingeniously done, the conditions of the ex- 

 periment are entirely changed ; for then Amperian repulsion 

 and angular currents act in direct opposition to each other, 

 and we are then at liberty to decide, .from the direction of the 

 motion which actually takes place, to which force the motion 

 ought to be attributed. 



I do not see how it follows, as Prof, van Breda and others 

 seem to suppose, that, because two currents at all possible angles 

 affect each other, they must do the same when they are both 

 on the same straight line; because if they act only in right lines 

 from their sides, no effect can possibly take place when they are 

 both on the same straight line. In this case a curved line would 

 be required to produce the effect. 



The experiment of Prof, van Breda with the reversed con- 

 ductor, and some others detailed by him, certainly prove that the 

 molecules of a conductor, while the current is passing, do repel 

 each other ; but still this fact does not appear to settle the real 

 question at issue ; for it does not follow that, because the mole- 

 cules of the conductor along which the current passes recede 

 from each other, the contiguous parts of the current itself 

 repel each other. Our conceptions of the nature of the electric 

 current, as well as the facts from which these conceptions are 

 derived, are in direct opposition to this conclusion. 



Whether we view electricity as a substance or merely a dyna- 

 mical affection of the ordinary molecules of matter — in fact what- 

 ever our views of its nature are, it will be admitted that the elec- 

 tric current is an effort of forces to regain a state of equilibrium. 



