240 Mr. Lane on Electric Conduction in Metals. 
excited by the current. This was shown by doubling a wire so 
as to form two conductors joined at one end without solder, in 
which case the fluctuations disappeared at that end. This ther- 
mo-electric action, if constant, would not, however great, — 
the accuracy of the experiment. 
19. It is important to remember that the above law cannot, 
according to the present state of our knowledge, be generally ap- 
plied to the case of momentary currents, such as the Leyden dis- 
charge, or the spark from the prime conductor of an electric ma- 
chine, or induced currents at the making or breaking of a gal- 
vanic circuit. In such cases the induction of electric currents on 
themselves must interfere. If however we assume that at a con- 
stant distance the force of induction in a given length is propor- 
tional to the rate of increase or diminution of the current,* it will 
follow that two conductors of the same section but. different 
lengths, will divide an electric discharge between them in the 
inverse ratio of their lengths, and in this case no error will be 
involved in the application of the law. But when we come to 
vary the section, it would probably be found to fail, the smaller 
section having the advantage. Or if the form only of the sec- 
tion were varied, in which case the advantage would probably be 
in favor of that which departed most from a circle. 
20. The inquiry might arise whether these things should not 
be taken in view, in considering the theory of the discharges 
through telegraphic wires. 'The question in this ease is whether 
e inductive action of the current on itself may not in those 
very long wires so much retard its increase as to prevent its as- 
suming its maximum quantity during the time of a discharge by 
the key. Now if the assumption already made (¢ 19) be true, it 
will follow that in a conductor of given section and conducting 
power, the time in which the current will reach its maximum 
under a constant electro-motive force will be independent, not 
only of the length of the conductor, but of the motive force 
itself. Indeed in mathematical strictness, the current woul 
never reach its maximum under a constant motive force, but 
sutibiduneianie 
umes xxxviii and xli, of the first series of this Journal. See also Faraday’s Re- 
searches, vol. i, p. 2. 
