PROFESSOR KELLAND, ON MOLECULAR EQUILIBRIUM. 45 



hence B = Ae~ al {\ + al) + ^— -£, 



3 



and we obtain also, as in (14), 



%/r cB 4,irPB 



,, ,. " , a 2 i)if a 2 / 3 ? 



4,rP r 3 )' 



4>^AMPe- al (l+al) = M*_^ 4>7rMl 3 Pq 

 a 2 « 8 « 3 3 a 2 ' 



which expressions will simplify that for the force of two material par- 

 ticles on each other, by striking out several identical terms. 



7b find the mutual action of two particles of matter together with 

 the caloric surrounding them, on the hypothesis that matter is repulsive 

 towards caloric. 



25. Since the caloric surrounding the particle A, whose action on 

 B we are about to estimate, is diminished by ^4's repulsion, the ex- 

 ternal mass will no longer produce an effect equal in all directions, 

 whose actual value is therefore zero ; but will exert a force on B 

 equivalent to the attraction of a mass similar, and similarly situated to 

 the mass displaced. 



The set of forces, then, which act on B through the means of A, are 



(i). The repulsion of A on B. 



(2). The attraction of a mass of caloric equal to that displaced by 

 the volume of A. 



(3). The attraction of a mass of caloric equal to that displaced by 

 the repulsion of A, and 



(4). The pressure on the surface of B resolved in one direction 

 along the line joining the centres of A, B. 



26. If a be the distance between the centres of A and B, the 



M 2 

 expression for their repulsion is — 5- , which is the first force. 



