500 Mr. Exley's Remarks on M. Mossotti's Theory of Physics, 



Also from the assumption which Mossotti has introduced 

 into his calculations, viz. that the elasticity of the aether varies 

 as the square of its density, the insufficiency of his principles 

 may be inferred. For the density must be much greater near 

 the molecules than in free space, because the molecules 

 powerfully attract the aether, and retain very dense atmo- 

 spheres : hence also the density of the aether near a large body 

 of molecules must be much greater than in free space ; con- 

 sequently its elasticity in free space must be much less than 

 near the large body, being as the square of the density. But 

 by his first principles the elasticity in free space must be per- 

 fect, since all the atoms are within the sphere of each other's 

 repulsion, and no attraction exists among themselves, so that 

 whatever displacement is made by a force applied, the atoms 

 will restore themselves, when the disturbing force is removed, 

 by a force equal to that by which they were displaced : hence 

 the elasticity is both perfect and imperfect at the same time, 

 which is impossible. 



It seems as if Mossotti had assumed the universality of his 

 aether to please the undulationists; but they have no reason 

 to thank him, because it would completely undo their system, 

 which is obliged to allow the hypothesis, that the elasticity of 

 the aethereal medium is more imperfect in bodies than in free 

 space. 



Mr. Babbage further states that " the other conditions to 

 be satisfied are," 1st. " That the juxtaposition of such atoms 

 must in some circumstances form a solid body." 2nd. " In 

 other circumstances a fluid." 3rd. In other cases a gaseous 

 body—" The solid must possess cohesion, tenacity, malle- 

 ability, elasticity :" the other forms must possess capillarity, 

 and susceptibility of compression, without becoming solid, as 

 also elasticity, p. 166. He adds, 4th. The central atoms 

 must admit of a more intimate approach, so that their atmo- 

 spheres may unite, and form one atmosphere. (i Binary com- 

 pounds might then have atmospheres not quite spherical, thus 

 possessing polarity." 5th. " Combinations of three or more 

 atoms, as the central body of one atmosphere, might give great 

 variety of attractive forces." 6th . " Two or more central atoms 

 uniting, might either not be able to retain the same amount 

 of atmosphere, or they might possibly be able to possess a 

 larger quantity." p. 166. and 167. 



Corresponding with these, it will be found in my treatise, 

 1st. That some bodies will have the solid form; prop. 19. 

 2nd. Others will have the liquid form ; p. 20. 3rd. And others 

 the gaseous form ; p. 21. See also pages 60, 93, 103 and 105. 

 4th. That if two tenacious atoms with their atmospheres be 



