154 Rutherford: Modern 



ether. Larmor has supposed that the electron consists 

 of a strain center in the ether, which is transferred 

 through the medium in somewhat the same way as a knot 

 can be slipped along a rope. Such a theory, however, 

 presupposes the existence of the corresponding and com- 

 plementary positive electron. This difficulty in regard 

 to the difference between positive and negative elec- 

 tricity is well illustrated by the attempts that have been 

 made to form a mechanical or rather electronic model 

 of the chemical atom. In a remarkable paper called 

 "Aepinus atomized," published by Lord Kelvin in 1903, 

 but whose title I think we might in justice change to 

 " Franklin and Aepinus Kelvinized," Lord Kelvin 

 adopted the fundamental conception of the one fluid 

 theory of Franklin, as modified by Aepinus, and applied 

 it to the atom of matter. The atom was supposed to con- 

 sist of a number of mobile negatively charged particles 

 or electrons, held in equilibrium by a system of mutual 

 forces, similar to that devised by Aepinus in mathemat- 

 ically developing Franklin's theory. Since an atom is 

 electrically neutral, and must consist of an equal quan- 

 tity of positive and negative electricity, such a view was 

 equivalent to supposing that the atom consists of a num- 

 ber of mobile negative electrons embedded in a sphere 

 of positive electrification. This conception of atomic 

 structure devised by Lord Kelvin has been still further 

 developed by J. J. Thomson. The latter has mathemat- 



