X.—ON THE POSSIBILITY OF ORIGINATING WAVE DISTURBANCES 
IN THE ETHER BY MEANS OF ELECTRIC FORCES. 
BY 
GEO. FRAS. FITZGERALD, m.a., F.1.c.D. 
[Read November 17th, 1879. ] 
Ix Professor J. Clerk Maxwell's most admirable treatise on Electricity and 
Magnetism the following expression occurs—(§785) :—“ Let us suppose that when 
t [time] is zero the quantities A and A are zero except within a certain space 8,” 
and he proceeds to show that this will give rise to an electrical disturbance propa- 
gated in free space with the velocity of light. Some doubt as to the possibility of 
producing a distribution of currents which would originate such disturbances was 
aroused in my mind by the following consideration: for the validity of the 
deduction it is necessary that the whole space considered be non-conducting. Now, 
Gauss showed long ago that such a quantity as the potential of any system of 
attracting bodies cannot have a zero value throughout one part of space and 
another value in any other communicating part. The components of A, the vector 
potential of the electric current, are of the same form as the potentials of attracting 
bodies, and could not consequently fulfil the condition Professor Maxwell assumes. 
Though this does not include the case of currents distributed throughout space, 
such as the changes of electric displacement which Professor Maxwell supposes to 
be currents, yet, I believe, that the reasoning may be extended to this case also. 
Further, it has to be shown that no other possible assumed distribution would give 
rise to disturbances propagated in time throughout space. 
If we investigate how such disturbances could be originated by combinations of 
currents and charges on fixed or moveable conductors and non-conductors it is in 
the first place to be observed that we may legitimately assume the conductors to be 
perfect conductors, for the heating of a conductor by an electric current, as far as 
it is a production of wayes in the ether, is according to Professor Maxwell's hypo- 
thesis, one of the very things whose origin we want to find out, and as far as it is 
only an increased motion of matter is not related to the question in hand. 
Now, if any system of conductors, moveable or fixed, could give rise to the pro- 
duction of disturbances propagated throughout space, in time the energy of the 
system would become gradually expended in the same manner as heat is when a 
hot body cools. Another effect of such a system would be, that at each point of 
space there would generally be a double action, one the direct inductive action 
