Electric Origin of Molecular Attraction. 627 



Laws of Thermochemistry," xl., " Molecular Force and the 

 Surface-Tension o£ Solutions," xl., " The Molecular Consti- 

 tution of Water," 1. ; and series [6] " Ionization, Ionic Velo- 

 cities, and Atomic Sizes," iii. The scope of the present 

 paper is outlined in the following Table of Contents : — 



1. Statement of the theory, consideration of difficulties, 



and a short digression on the Maxwell- Farad ay stresses 

 in the aether and cohesion of the sether. 

 la. The range of molecular force. 



2. Comparison of results with known laws of molecular 



attraction. 



3. Relation to HelmhoKVs theory of chemical valence. 



4. Period of rotation of an electric doublet. 



5. Electric doublets in different classes of chemical sub- 



stances. 



6. Molecular couples and gyrostats. 



1. Statement of the Theory. 



Briefly it is this : — That the electric doublets in molecules 

 exercise mutual directive actions as do magnets, so that the 

 nearer two neighbours approach the more do their electric 

 axes tend to take the same direction, and therefore on this 

 account they exercise a stronger attraction on one another ; 

 and also because attracting forces varying inversely as the 

 fourth power of the distance produce motion which increases 

 their strength, there are two causes which make the attractive 

 forces amongst a number of moving doublets of more dyna- 

 mical importance than the repulsive. To fix ideas we must look 

 more closely into the system of forces between two magnets. 



In Maxwell's l Electricity and Magnetism' (2nd edit.) 

 art. 387, we have Tait's results for the forces of magnets on 



magnets translated from quaternion into ordinary expressions. 

 Let A B and C D be two magnets of moments ra 2 and ?n 2 in 



2T 2 



