applied to Electric Currents. 291 
We have thus determined three quantities, F, G, H, from which 
we can find P, Q, and R by considering these latter quantities 
as the rates at which the former ones vary. In the paper already 
referred to, I have given reasons for considering the quantities 
F, G, H as the resolved parts of that which Faraday has conjec- 
tured to exist, and has called the electrotonic state. In that 
paper I have stated the mathematical relations between this elec- 
trotonic state and the lines of magnetic force as expressed in 
equations (55), and also between the electrotonic state and elec- 
tromotive force as expressed in equations (58). We must now 
endeavour to interpret them from a mechanical point of view 
in connexion with our hypothesis. 
We shall in the first place exaraine the process by which the 
lines of force are produced by an electric current. 
Let AB, Pl. V. fig. 2, represent a current of electricity in the 
direction from A to B. Let the large spaces above and below 
AB represent the vortices, and let the small circles separating 
the vortices represent the layers of particles placed between them, 
which in our hypothesis represent electricity. 
Now let an electric current from left to right commence in 
AB. The row of vortices gh above AB will be set in motion 
in the opposite direction to that of a watch. (We shall call this 
direction +, and that of a watch —.) We shall suppose the 
row of vortices k/ stillat rest, then the layer of particles between 
these rows will be acted on by the row g/ on their lower sides, 
and will be at rest above. If they are free to move, they will 
rotate in the negative direction, and will at the same time move 
from right to left, or in the opposite direction from the current, 
and so form an imduced electric current. 
If this current is checked by the electrical resistance of the 
medium, the rotating particles will act upon the row of vortices 
Kl, and make them revolve in the positive direction till they 
arrive at such a velocity that the motion of the particles is reduced 
to that of rotation, and the induced current disappears. If, now, 
the primary current A B be stopped, the vortices in the row gh 
will be checked, while those of the row k / still continue in rapid 
motion. The momentum of the vortices beyond the layer of 
particles p g will tend to move them from left to right, that is, 
in the direction of the primary current; but if this motion is 
resisted by the medium, the motion of the vortices beyond pq 
will be gradually destroyed. 
It appears therefore that the phenomena of induced currents 
are part of the process of communicating the rotatory velocity of 
the vortices from one part of the field to another. 
[To be continued. ] 
U2 
