On Electromagnetic Effects due to the Motion of the Harth. 323 
2.¢., itg components are 
fy dhe 
X=cv—bw + e(cy — bz) ee ay OTR 
f oo KEP GRD 
Y=aw—cu+ e(az— ea) — ee —e ay 
dH GE 
Z—bu—av + e(bx — ay) —e——= = os 
Now when there is no conduction current at the point w=v=w=0. For it would 
evidently be improper to include e twice over, first as a quantity of electricity, and 
secondly as a current. In the equations as I give them, the eflect of the motion 
of e is included under e V 8p, 7.e., in the components, as e (cy —bz), &c. Hence we 
get that if there be no conduction current at the point but only this convection 
current, the mechanical force is completely represented by 
o—e& 
2.€., its components are 
X—eP 
Y=eQ 
Z=eR 
and that there will consequently be no mechanical force at points where the electro- 
motive intensity vanishes. 
It has just been shown that the electromotive intensity vanishes at a point 
outside a magnet, moving with the same velocity as the magnet, and I hence 
conclude that there would be no force on an electrified body moving with the 
magnet. 
If we consider the electrified body as acting on the magnet, we are led to a 
similar result. In this case the moving electricity has an electromotive intensity 
2 "20 
uf [Pie . dx dy dz dé dn de 
oe @ 
“or as VS J I J yl dy dz 
i @ @ 
Caps) Vo didn dé 
2.e., its components are, 
PH pf f/vn di dy dé 
Q=pn/// vy dé dn dé 
Rap /ff¥z dé dy de 
Hence if ¥ be constant all over any space, the magnetic force vanishes throughout 
that space. Now ¥ must be constant all over the inside of a magnet. Hence we 
see that the electricity induced on the outside of a magnet by externa electricity 
moving with it, exactly neutralises both the electrostatic and electromagnetic 
actions of the external electricity on the inside of the magnet. We thus see that 
the magnetism inside the magnet, and the convection current outside are related 
* It may be worth while remarking that the actions of convection currents which, with Maxwell’s 
-equations, seem to need an additional assumption, come out as obvious results of the equation as here 
given. 
