124 DIRECT PROPERTIES OF MOLECULES 351 



Kelvin and Tait, 1 Kirchhoff, 2 and Boltzmann 3 have 

 shown in their mathematical papers, rings and other bodies 

 which are in a moving liquid experience an apparent 

 attraction which is comparable with electrodynamic attrac- 

 tion. 



All this holds good even if the vortices have not the 

 shape of rings or of unlimited threads. The same forces are 

 also originated by masses, and act between masses which 

 move in different ways. We may therefore also form 

 other similar conceptions of the atoms which correspond 

 better to the/views that have been put forward since very 

 old times.vOf this nature is the hypothesis of pulsating 

 atoms, which we may look upon as spheres, or bodies of 

 some similar shape, in such a state of motion that regular 

 oscillations, perhaps in the radial direction, go on at every 

 point within them. Bjerknes has mathematically investi- 

 gated the forces brought into play by such motions, and 

 S.c h i 5jtzjias experimentally examined them. 4 



On both these theories the force exerted by one atom on 

 another would be transmitted by the medium that lies 

 between them without motion and therefore powerless and 

 weightless the luminiferous ether in fact. The close rela- 

 tions which have been recognised of late years between 

 light and electricity suggest the idea of supposing the forces ^> 

 between the atoms which are transmitted by the ether to be 

 of electrical nature, and of taking the motions inside the 

 atoms, to which the atoms owe their force and nature, 

 to be also of electrical character. These suppositions have 

 often been made, especially by W jj&cjieri 5 and Prince 

 Galitzin. G 



ijTach. of these theories, whether referring the force 

 between atoms to hydrodynamical motions or to electrical 



1 Treatise on Natural Philosophy, Oxford 1867, i. p. 264; 2nd ed. 

 Cambridge 1879, i. p. 330. 



2 Crelle-Borchardt's Journal, 1870, Ixxi. pp. 237, 263. 



3 Ibid. 1871, Ixxiii. p. 111. 



4 Gott. Nachr. 1876, Nr. 11 ; 1877, Nr. 13. F. Auerbach, Theoret. Hydro- 

 dynamik, 1881. 



5 Schriften d. phys.-oUon. Ges. zu Konigsberg, 35. Jahrg. 1894 ; Sitzungsber. 

 p. 4 ; 37. Jahrg. 1896, p. 1. 



6 Bull, de VAcad. de St. Petersb. 1895 [5] iii. p. 1. 



