116 MOLECULAR FORCES. [SECT. xiv. 



electric fluid ; and that, while the electric atoms repel one 

 another, they are attracted by the material molecules of the 

 body. These forces of attraction and repulsion were after- 

 wards proved by Coulomb to vary inversely as the squares of 

 the distance. * The hypothesis of Franklin was reduced to a 

 mathematical theory by ^Epinus, and the most refined ana- 

 lysis has been employed by the Baron Poisson in explanation 

 of electric phenomena. Still these philosophers were unable 

 to reconcile the attraction of the molecules of matter in- 

 versely as the squares of the distance, as proved by Newton, 

 with their mutual repulsion according to the same law. 

 But Professor Mossotti has recently shown, by a very able 

 analysis, that there are strong grounds for believing that 

 not only the molecular forces which unite the particles of 

 material bodies depend on the electric fluid, but that even 

 gravitation itself, which binds world to world and sun to sun, 

 can no longer be regarded as an ultimate principle, but the 

 residual portion of a far more powerful force generated by 

 that energetic agent which pervades creation. 



It is true that this connection between the molecular 

 forces and gravitation depends upon a hypothesis; but in 

 the greater number of physical investigations some hy- 

 pothesis is requisite in the first instance, to aid the imper- 

 fection of our senses. Yet, when the phenomena of nature 

 accord with the assumption, we are justified in believing it 

 to be a general law. 



As the particles of material bodies are not in actual con- 

 tact, Professor Mossotti supposes that each is encompassed 

 by an atmosphere of the ethereal fluid ; that the atoms of the 

 fluid repel one another ; that the molecules of matter repel 

 one another, but with less intensity; and that there is a 

 mutual attraction between the particles of matter and the 

 atoms of the fluid. Forces which we know to exist, and 

 which he assumes to vary inversely as squares of the distance. 

 The following important results have been obtained by the 

 Professor from the adjustment of these three forces : 



