Conductors conveying Steady or Transient Currents, 237 



minations), it will be better to use round wires rather than 

 strips, because linear dimensions then come in only under a 

 logarithm, and moreover are such as can be measured with 

 considerable accuracy without difficulty. Some of Mr. Boys' 

 quartz-fibre and aluminium-tube devices ought to permit the 

 zero of force to be sharply got, and thus a good measure of 

 a v " to be made. 



We should have to observe very exactly the neutralization 

 of all force between the suspended and fixed conductors while 

 a steady current was passing through them, with an interposed 

 wire of known resistance, and then use the relation (3) or (3') 

 in the form 



or 



u »>_ Si R __ resistance of wire expressed as a velocity , . 



8 P 

 If the acting conductors are set very near each other, a 

 being still the distance between their centres, the denominator 

 alters itself a little, becoming 



a*-2^ + ay(a*-y) 

 1 l0 S If ' 



with an easy additional complication if it is convenient to make 

 the sectional radii unequal*. 



By filling the vessel containing the acting conductors with 

 other insulating media, it is possible that the "w" for them 

 could be directly measured. 



Action of Moving Charges and Pulses. 



So far I have not taken into account the sinuosity of dis- 

 tribution of Leyden-jar discharges in space, nor the possibility 

 of pulses passing the two portions of the circuit between 

 which the force is being observed at different times or in 

 different phases. It would seem as if a small assemblage of 

 short-waved pulses sent round a long circuit might be pre- 

 vented from exerting any mechanical action on each other if 

 the adjacent parts of the circuit in which their action was to 

 be observed were purposely separated by an intervening length 

 of wire of many wave-lengths unsym metrically introduced 

 into the circuit. But before committing myself I should 

 like to make a few experiments. Nevertheless I am tempted 

 to go on a little further. 



If instead of considering pulses rushing along stationary 

 wires, we consider charged wires moving along endways with 



* See Foster and Lodge, Phil. Mag. June 1875, p. 456. 

 Phil. Mag. S. 5. Vol. 30. No. 181. Sept. 1890. S 



