HIDiiX 



H 



THE 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] 





4? 



'■ 



MA Y 1909. 





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LX. The Electric Origin of Molecular Attraction. 

 By William Sutherland *. 



IN connexion with this subject there is one chief out- 

 standing difficulty to be discussed in this communication. 

 Its nature will appear in the following few facts from the 

 recent history of the subject. In a series of articles in this 

 Magazine, beginning in August 1886 ([5] xxii. p. 81), I 

 brought forward the evidence in support of the law of the 

 inverse fourth power for molecular attraction, which may be 

 written 3A??i 1 m 2 /r 1 in analogy with the Newtonian law of 

 gravitation. It appeared subsequently that this analogy 

 did not hold good in fact, that the attracting powers of 

 molecules do not depend directly on their masses, and there- 

 fore that 3Aw]/»o should be replaced by Sc^o^ in which a x 

 and a 2 are parameters characteristic of the molecular masses 

 m x and m 2 attracting one another. In connexion with this 

 law of the inverse fourth power I was naturally led to give 

 much consideration to the fact that the attraction between 

 two small magnets similarly directed along a straight line 

 varies inversely as the fourth power of the distance between 

 their centres, that a similar result holds for atomic vortexes, 

 and also for molecules containing separated electrons of 

 opposite sign, for the significance of the electron had been 

 emphasized in Helmholtz's Faraday lecture. But the great 

 difficulty of connecting molecular attraction with these results 

 for polar pairs was this, that polar pairs when oppositely 



* Communicated by the Author. 

 Phil. Mag. S. 6. Vol. 17. No. 101. May 1909. 2 Y 



