713 
MR. G. F. C. SEARLE OR PROBLEMS IN ELECTRIC CONVECTION. 
thought that this amount of work would be equal to the sum of the electric and 
magnetic parts of the energy of the system, i.e., to U + T. But instead, we have 
i9*i - i9*i = u - T. 
The discrepancy arises from the fact that there must be an expenditure of direct 
electric and magnetic energy while the system is being collected, in order to maintain 
in its proper strength the system of displacement and magnetic currents which 
accompany each moving elementary charge. 
This transformation enables us to determine the energy of any system for which 3' 
is known, with only one troublesome integration, viz., the space summation of 
juH 3 /47T. 
If the surface corresponding to the suffix 2 is at an infinite distance from the 
surface corresponding to the suffix 1, it will generally happen that Tq = 0, and then 
we have for the energy 
W = 2T + . ... . (94) 
where M? now refers to the finite surface. 
In conclusion, I have much pleasure in expressing my best thanks to my friend, 
Mr. Oliver Heaviside, F.R.S. Besides giving me some personal instruction in 
Electromagnetic Theory on several occasions, he has constantly encouraged me 
during the progress of this investigation. 
4 Y 
MDCCCXCVI. — A 
