426 SCIENCE PROGRESS 



With these fundamental assumptions for electron theory it 

 is interesting to find how great a range of physical actions are 

 illustrated by simple combinations of electrons and atoms in 

 his article "Aepinus Atomised," Baltimore Lectures, Appendix 

 E, 1901, and later papers. Electrification by contact between 

 different substances and electrification by friction appear as 

 actions in which a smaller atom robs a larger of its electron. 

 The difference of potential energy of a system of two dissimilar 

 atoms in their initial and final configurations represents the 

 energy radiated in the impulses occurring in the process of 

 separation and in the oscillations preceding the final settlement 

 in the new equilibrium position. It is thus a constant for each 

 encounter of atoms. The positions of equilibrium and con- 

 ditions of stability of equilibrium for various numbers of 

 electrons within an atom are discussed for systems involving 

 as many as twenty-one electrons. The possibility of more than 

 one position of equilibrium for a given number of electrons, 

 and the definite amount of potential energy radiated in a change 

 to the more stable configuration, are points of interest in relation 

 to the requirements of recent theory. Similar questions of 

 stability appear earlier in Lord Kelvin's work in connection 

 with crystalline configurations and with respect to the equi- 

 librium of groups of columnar vortices revolving round their 

 common centre of gravity illustrated by Mayer's well-known 

 experiment with floating magnets of 1878. These questions 

 have been dealt with mathematically by Prof. J. J. Thomson 

 in his "Motion of Vortex Rings" of 1883, and in more recent 

 papers (in the Phil. Mag., 1904 and later), where valuable illus- 

 trations of possible mechanics of radiation and radioactivity 

 are given, involving suggestions as to emission of energy 

 occurring in the passage of a system from one stable con- 

 figuration of motion to another involving less kinetic energy. 

 Quite recently, too, the structure of an atom has been given 

 in which emission of energy takes place in discrete quanta in 

 accordance with Planck's theory of radiation. The investi- 

 gations of the same author on the corpuscular theory of matter 

 prove that the capacity of the electron theory to account for atomic 

 weights is probably much greater than Lord Kelvin supposed. 

 Taking only the positions of equilibrium of electrons in one 

 plane, and assuming that atomic weight is proportional to the 

 number of corpuscles in the atom, it is possible to obtain a 



