288 
PROFESSOR J. H. POYNTTNG ON ELECTRIC CURRENT AND THE 
this is not the case, for in those experiments the tubes reached air breaks near the 
two ends of the wire before they reached a break in the middle. 
We cannot by this general reasoning show that the energy entering any length of 
the wire will be proportional to the resistance of that length—the result obtained by 
Riess. Indeed, this cannot always be the case. For instance, imagine a condenser 
discharged by two wires connected to the two plates of another condenser of greater 
capacity, whose plates are again connected by a fine wire of enormous resistance, 
through which the discharge can only take place slowly. Then the energy dissipated 
in the wires will not to a first ajiproximation depend on their resistances but on the 
ratios of the capacities, that in the wire of high resistance bearing to that in the other 
wires the ratio of the less capacity to the greater. Probably Riess’s results only hold 
when the discharge takes place in such a way that it may be looked upon at any one 
moment as approximately in the steady state. 
We have shown that the magnetic measure of the total current is the same all along 
the wire. Probably also the chemical measure is the same—meaning by the chemical 
measure whatever interchanging or turning round of molecules may occur when 
induction takes place in a conductor. For even if a tube does not enter the wire at 
the same time throughout its length, an end part, say, entering first, the point of 
attachment of the tube to the conductor being transferred from the plate to somewhere 
along the wire, this transference of the point of attachment from molecule to molecule 
implies the same amount of chemical change within the wire as if the tube entered 
all at the same moment. It will not, however, take place equally throughout the 
cross section as it does in the steady state. 
Probably we only have the simultaneous disappearance of all parts of a tube when 
the wire follows a line of electric induction, and has its resistance per unit length 
proportional to the intensity which would exist there if the wire were removed. 
The hypothesis here advanced is in accordance with Maxwell’s doctrine of closed 
currents. For the induction dissipated at one part of the circuit has come there from 
another part where relatively to the circuit it ran in the opposite direction. The total 
result is equivalent to the addition of so many closed induction tubes to the circuit, 
the induction running the same way relatively to the circuit throughout. 
If the two plates of the condenser are not connected by a wire but are discharged 
gradually by the imperfect insulation of the dielectric, then we must suppose that the 
tubes of induction in this case are dissipated in situ, the induction simply decaying at 
a rate depending on its amount and upon the conductivity of the dielectric. We may 
still represent this process by a closed current by regarding the loss of induction 
^Maxwell’s — and the quantity of induction dissipated (Maxwell’s p), as 
df 
two different quantities. We have then P+~y — 0 or we have two equal and opposite 
currents. But this seems artificial. It is more natural to look upon the process 
