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LVII. Remarks on M. Mossotti's Theory of Molecular 

 Action*, 



COME years since a paper by M. Mossotti, on the forces 

 ^ which regulate the internal constitution of bodies, at- 

 tracted a good deal of attention among scientific men. A 

 translation of it appeared in the third part of the ' Scientific 

 Memoirs.' The author's object was to develope the views of 

 Franklin and iEpinus with respect to electricity. It is well 

 known, that in the form which the latter of these philosophers 

 gave to the single fluid hypothesis, a mutual repulsion is sup- 

 posed to exist among the material molecules of which bodies 

 are composed, as well as among the particles of the electrical 

 aether; while these particles are supposed to be attracted by 

 the material molecules. Assuming that all the forces required 

 by the hypothesis vary directly as the mass and inversely as 

 the square of the distance, is it possible to establish stable 

 equilibrium among the molecules of which bodies are com- 

 posed ? This is the question which M. Mossotti proposed to 

 determine. 



A priori, stable equilibrium certainly appears to be possi- 

 ble ; for, as the author remarks, if the molecules of matter sur- 

 rounded by their atmospheres attract each other when at a 

 distance, and exercise a repulsive force when brought nearer 

 together, there must be some intermediate position of stable 

 equilibrium. But although M. Mossotti's general view may 

 be correct, I believe it will be found that his analysis is erro- 

 neous. As the subject of molecular attraction possesses at the 

 present day a good deal of interest, I trust that I may be per- 

 mitted to develope at some little length my objections to M. 

 Mossotti's investigation. For this purpose it will be neces- 

 sary to follow his analysis as far as the reduction of the pro- 

 blem to equations. 



Lety be the coefficient of the repulsion between any two 

 atoms of the aether ; g the coefficient of the attraction between 

 an atom of the aether and a material molecule ; and y the co- 

 efficient of the repulsion between two material molecules. 



Again, let q be the density of the aether at a point x y z, 

 and s the elastic force or pressure at the same point, referred 

 to the superficial unit. Let it be the density at a point £ >j £ 

 of a molecule supposed to be of certain though very small di- 

 mensions. 



All the forces of the system may be represented by the 

 partial differential coefficients of the following definite inte- 

 grals : — 



* Communicated by the Author- 



