1824.] . the Combination of Potassium and Oxygen. 207 



Boscovich has presented it under a different form, and which, 

 if it were correct, would readily explain the phenomenon under 

 consideration. He supposes the particles of matter to attract 

 each other, and the force of attraction at all greater distances to 

 be smaller than at nearer distances, and to repel each other, by 

 reason of the elastic force of caloric, the repulsive force dimi- 

 nishing more than that of attraction, when the distances are 

 increased ; he supposes that upon the surface of a particle of 

 matter, the repulsive force is greater than the other ; hence at a 

 certain distance, there will be an equilibrium, and this will be 

 the distance of the particles from each other. Having made this 

 supposition, he thus accounts for the force of cohesion : the par- 

 ticles, being at that distance from each other at which the oppo- 

 site forces are equal to each other, are at rest. If a force be 

 applied which tends to separate the particles from each other, 

 if their distance be by it increased by the smallest quantity, an 

 attracting force resists it, which force is called cohesion, because, 

 since the force of repulsion varies inversely as some higher 

 power of the distance than attraction does, beyond the distance 

 at which there is an equilibrium, the force of attraction is greater 

 than the other. Were this hypothesis accurate, the phenome- 

 non might be explained ; but there are many serious objections 

 to it. When particles are balanced by the equilibrium of two 

 opposite forces, they will constitute a liquid, but never can form 

 a solid ; because they have perfect freedom of motion round each 

 other, will yield to every impulse, arrange themselves so as to 

 have a horizontal surface, by the action of gravitation, and press 

 upon the vessel containing them equally in all directions ; all 

 which are properties of liquid substances, but have no resem- 

 blance whatever to those of solids. Besides, a long rod of 

 metal ought to be visibly stretched by a very small force, and 

 the cohesive force ought to increase continually, until the very 

 instant of its being overcome. Again, suppose the distance 

 between two adjacent particles to have any assumed ratio to the 

 diameter of either of them, in any given solid ; form two equal 

 Jar^e solids of the same substance, and suppose the force of 



attraction to vary as =— (D being the distance from the centre) ; 



place these at such a distance that they shall be similarly situated 

 to the particles of the solid; then if d be the distance between 

 two particles, since in both cases the diameters are proportional 

 to the distances, the force of attraction between two particles : 



force between the spheres :: - : — , so that unless the attraet- 



r d« D"' 



ive force vary inversely as a higher power of the distance than 

 the fifth, the attraction between the spheres must be very great; 

 for although no force is visible at the distance d, since the 

 forces are equal and opposite at that distance, the forces must 



