140 CHEMICAL AFFINITY. 



ing the variation. But every such variation in distance must 

 occasion a corresponding variation in the intensity of the attracting 

 force. It may be, then, that barytes attracts sulphuric acid with 

 greater intimity than potash, because the particles of barytes, 

 whon they act upon the acid, are at a smaller distance from it than 

 the particles of the potash are. 



But it may be asked, Why, if barytes, potash, and sulphuric acid, 

 are all mixed together in water, th- particles of potash do not ap- 

 proach as near the acid as those of the barytes, since they are both 

 at liberty to act ? To this it may be answered, that in all proba. 

 bility they do approach each of them to the same apparent dis- 

 tance, (if the expression be allowed), but that, notwithstanding, 

 their real distance may continue different. The particles of bo. 

 dies, how minute soever we suppose them to be, cannot be desti- 

 tute of magnitude. They must have a certain length, breadth, 

 and thickness, and therefore must always possess some particular 

 figure or other. These particles, indeed, are a great deal too mi. 

 nute for us to detect their shape ; but still it is certain that they 

 must have some shape. Now it is very conceivable that the par. 

 tides of every particular body may have a shape peculiar to them, 

 selves, and differing from the shape of the particles of every other 

 body. Thus the particles of sulphuric acid may have one shape, 

 those of barytes another, and those of potash a third. 



But if the particles of bodies have length, breadth, and thick, 

 ness, we cannot avoid conceiving them as composed of an inde- 

 terminate number of still more minute part'cles or atoms. Now 

 the affinity of two integrant particles for each other must be the 

 sum of the attractions of all the atoms in each of these particles 

 for all the atoms in the other : but the sum of these attractions 

 must depend upon the number of attracting atoms, and upon the 

 distance of these atoms from each other respectively ; and this dis. 

 tance must depend upon the figure of the particles. Ftr it is ob. 

 rious, that if two particles, one of which is a tetrahedron and the 

 other a cube, and whi'-h contain the same number of atoms, be 

 placed at the same relative distance from a third particle, the sum 

 of the distances of all the atoms of the first particle from all the 

 atoms of the third particle, will be less than the sum of the dis- 

 tances of all the atoms of the second particle from those of the 

 third. Consequently, in this case, though the apparent distance 

 of the particles be the same, their real distance is different ; and 



