THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] 



SEP TEMBER 1907. 



XXVIII. On the Motions of Ether produced by Collisions of 

 Atoms or Molecides containing or not containing Elecirions. 

 By Lord Kelvin*. 



§ 1. T>Y atom is meant an indivisible element o£ ponderable 

 .JD (gravitational) matter, or of electricity ; by mole- 

 cule, an assemblage of two or more ponderable atoms, held 

 together by mutual attractions balanced by mutual repulsions. 



§ 2. In the atomic theory o£ electricity, electrion means an 

 atom of resinous electricity, commonly hitherto called nega- 

 tive electricity. It is at present commonly assumed, and I 

 believe in all probability rightly assumed, that all electrions 

 are equal and similar. 



§ 3. An ancient hypothesis, which has had large considera- 

 tion among philosophers in all times, assumes that there is 

 only one kind of atom, and that groups of equal and similar 

 atoms constitute the chemical elements, with all their 

 marvellous variety of quality. But, though no doubt some 

 important and interesting differences of quality, such as the 

 difference between ordinary, and red, phosphorus, are due to 

 differences of grouping in assemblages of one kind of atom, 

 it seems extremely improbable that differences of grouping 

 of atoms all equal and similar suffice to explain all the different 

 chemical and other properties of the great number of sub- 

 stances now commonly called chemical elements. It seems 



* Communicated "by the Author, having been read before Section A 

 of the British Association, August 1, 1907. 



Phil. Mag. S. 6. Vol. 14. No. 81. Sept. 1907. Z 



