W. A. Norton on Molecular Physics. 71 
C here represents the constant intensity of the impulsive force 
of the magnet, for one curve. The value of C decreases as the 
distance of the curve from m, fig. 9, increases. The equation (b) 
shows that for the larger curves, except near the magnet, afe+ 
bfd, must vary in nearly the same ratio with the ordinate y, 
from one point to another of the curve. To the left of the line 
ak the arc afc becomes negative in equation (b). Equations (a) 
and (c) fail for y=0. 
e investigation here made proceeds upon the supposition 
that the breadth of the magnet is indefinitely small. If wesup- 
pose it to be indefinitely great, the action of each individual 
transverse current upon any point, 7, fig. 10, would be inversely 
proportional to the distance of the current from this point, and 
it will be readily seen that the amount of force propagated to /, 
within any angle, as mfr’, will be the same whatever may be 
the value of fn. . 
The equation for the value of the effective impulsive force will 
be approximately of the form 
i? 
wk (- +3) ; 
k being a constant coefficient dependent upon the strength of 
the magnet,—/ and 1’ the parts of the length, a}, of the magnet, 
genet. 
Let us now replace Faraday’s lines of force by the curves of 
er what should 
ms, mt, &c., (fig. 9). : ; 
t is obvious that if the movement be outward, the impulsive 
force taking effect upon the wire will decrease ; and that if it be 
inward, the force will increase. Hence, agreeably to the funda- 
mental principle before alluded to, (p. 67,) in the first case there 
should be an induced current having the same direction as the 
currents of the upper face of the magnet; and in the secon 
case a current pursuing the opposite direction. Again, the 
amount of change of force which results from the displacement 
of the wire, and therefore the quantity of electricity whi 
this charge sets in motion, should depend solely upon the 
number of curves traversed. We may add that in whatever 
part of the magnetic field, and in whatever direction the wire be — 
* The individual molecular currents lying in a transverse section of the magnet, 
are here supposed to be replaced by two linear currents transverse to the magne 
one in the upper and the other in the lower surface. ee ik 
