238 Proceedings of the Royal Society of Edinburgh. [Sess. 
This last question is of some interest in the theory of atomic structure ; 
a number of writers have laid stress on the importance of mutual electro- 
magnetic mass, and in particular Harkins and E. D. Wilson * have used 
this phenomenon to explain the departure of atomic weights from whole 
numbers. It appears, however, that such an explanation could alone be 
valid if mutual mass were ponderable. 
12. The theory of Faraday tubes might possibly be employed with 
advantage in other investigations connected with atom theory. Sir J, J. 
Thomson f has made several suggestions of this nature ; his conception of 
the electron as possibly simply the end of a single Faraday tube would of 
course have very important consequences if adhered to in any theory of 
atomic structure. 
Again, if we suppose that electrons and positive nuclei have the property 
of excluding the tubes of other electrons and nuclei, the attractions between 
particles of opposite sign would become a repulsion at very small distances. 
Or we may suppose that some or all of the tubes of an electron in an atom 
simply end at a nucleus, instead of spreading equally outwards in all 
directions ; and different states of an atom, with different periods of 
vibration, might arise according to the number of tubes so connected. 
Suggestions have also been made as to the application of the theory in 
connection with a possible discrete structure in radiation. J 
Conclusion. 
13. It has been shown that the general equation of the Maxwell-Lorentz- 
Heaviside theory of electro-magnetism can be derived as macroscopic con- 
sequences of a simple dynamical theory of Faraday tubes. 
This theory also gives explicit and non-contradictory expression to the 
ideas of electro-magnetic stress, momentum, and flux of energy/, and an 
electro-mechanical picture of radiation explaining the law of uniform pro- 
pagation in spite of the motion of the source. 
A number of suggestions are made as to applications to tlie theory of 
gravitation and other problems. 
Hawks Battaliox, 
Royal Naval Division. 
* Phil. Mag., Nov. 1915, p. 723. 
t Phil. Mag. (6), xxvi, p. 792. 
I Jeans, “ Report on Quantum Theories,” Proc. Lo7id. Phys. Soc., 1915. 
