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PROFESSOR J. H. POYNTIHG OR ELECTRIC CURRENT AND THE 
The energy being dissipated in the wire, the cell will continually send out fresh 
energy, the induction tubes, which proceed from the acid to the zinc, diverging out¬ 
wards in the same way as described in the discharge of a condenser. They bend 
round, and finally go into the circuit, the energy they carry being used for the 
necessary molecular changes, and finally appearing as heat in the circuit—except at 
the copper-acid contact where there is a crowding in of level surfaces, and therefore a 
convergence of more energy, which is recpfired to set the hydrogen free. 
At the same time magnetic ring-shaped tubes will be continually sent out from the 
zinc-acid contact, expanding for a time and then contracting again on various parts of 
the circuit and also giving up their energy. 
There is, therefore, a convergence of tubes of electric induction on the circuit, running 
in the same direction throughout, viz., from copper to zinc outside the cell, and from 
zinc to copper inside, except between the zinc and acid, where there is a divergence 
of tubes in which the induction runs in the opposite way. But a divergence of 
negative tubes causes magnetic intensity in the same direction as, and may therefore 
be considered as equivalent to, a convergence of positive tubes. The current may 
therefore be said to go round the circuit in the same way throughout. 
The tendency to a steady state in which the current or the number of induction 
tubes broken up per second is the same at all parts of the circuit, admits of simple 
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explanation. We know, as the result of experiment given by Ohm’s law, that C=- 
where R is the resistance per unit length and E the electric intensity. Until we 
can explain the molecular working of the current, i.e., the mode in which the 
induction tubes are broken up, we must accept Ohm’s law as a simple fact. Let us 
suppose that we have not yet arrived at the steady state, so that in some part of the 
circuit the electric intensity is less than in the steady state, while in another part it 
is equal to it or greater. Let the steady value of the intensity be E, the actual value 
in the former part E', and in the latter E". By Ohm’s law the number of tubes 
absorbed by the wire per second is given by C' = E'/R, and C" = E"/E, i n the two 
parts respectively, so that O' < C" since E' < E'' or less tubes are being destroyed in 
the first than in the second part. But all the tubes are sent out from the source of 
the energy, and are only destroyed in the circuit, being otherwise continuous and 
with their two ends in the circuit. Hence, if more tubes are destroyed at one part 
than another, the parts of the tubes not yet destroyed will gather in the medium 
surrounding the part where fewer are destroyed, increasing the induction there, and 
so raising the intensity in the wire and therefore the number of tubes destroyed. 
The field can evidently only be steady when the number of tubes destroyed in all 
parts of the circuit is the same. 
But it does not follow that in the steady state each tube enters the wire along its 
whole length at the same moment. This would imply that the axis of the wire is a 
line of electric induction perpendicular everywhere to the level surfaces. If we draw 
