SKCT. xiv.] MOSSOTTl's THEORY. 117 



When the material molecules of a body are inappreciably 

 near to one another, they mutually repel each other with a 

 force which diminishes rapidly as the infinitely small dis- 

 tance between the material molecules augments, and at last 

 vanishes. When the molecules are still farther apart, the 

 force becomes attractive. At that particular point where 

 the change takes place, the forces of repulsion and attraction 

 balance each other, so that the molecules of a body are 

 neither disposed to approach nor recede, but remain in 

 equilibrio. If we try to press them nearer, the repulsive 

 force resists the attempt ; and, if we endeavour to break the 

 body so as to tear the particles asunder, the attractive force 

 predominates and keeps them together. This is what con- 

 stitutes the cohesive force, or force of aggregation, by which 

 the molecules of all substances are united. The limits of 

 the distance at which the negative action becomes positive 

 vary according to the temperature and nature of the mole- 

 cules, and determine whether the body which they form be 

 solid, liquid, or aeriform. 



Beyond this neutral point the attractive force increases 

 as the distance between the molecules augments till it at- 

 tains a maximum; when the particles are more apart, it 

 diminishes ; and, as soon as they are separated by finite or 

 sensible distances, it varies directly as their mass and in- 

 versely as the squares of the distance, which is precisely 

 the law of universal gravitation. 



Thus, on the hypothesis that the mutual repulsion between 

 the electric atoms is a little more powerful than the mutual 

 repulsion between the particles of matter, the ether and the 

 matter attract each other with unequal intensities, which 

 leaves an excess of attractive force constituting gravitation. 

 As the gravitating force is in operation wherever there is 

 matter, the ethereal electric fluid must encompass all the 

 bodies in the universe ; and, as it is utterly incomprehensible 

 that the celestial bodies should exert a reciprocal attraction % 

 through a void, this important investigation of Professor 



