SCT XIV. MOSSOTTPS THEORY. 99 



tear the particles asunder, the attractive force predom- 

 inates and keeps them together. This is what consti- 

 tutes 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 be- 

 comes positive vary according to the temperature and 

 nature of the molecules, and determine whether the 

 body which they form be solid, liquid, or aeriform. 



Beyond this neutral point, the attractive force in 

 creases as the distance between the molecules augments, 

 till it attains 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 inversely 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 mat- 

 ter, the ether and: the matter attract each other with 

 unequal intensities, which leave 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 uni- 

 verse ; and as it is utterly incomprehensible that the 

 celestial bodies should exert a reciprocal attraction 

 through a void, this important investigation of Professor 

 Mossotti furnishes additional presumption in favor of a 

 universal ether, already all but proved by the motion of 

 comets and the theory of light. 



In ae'riform fluids the particles of matter are more 

 remote from each other than in liquids and solids ; but 

 the pressure may be so great as to reduce an ae'riform 

 fluid to a liquid, and a liquid to a solid. Dr. Faraday 

 has reduced some of the gases to a liquid state by very 

 great compression; but although atmospheric air is 

 capable of a diminution of volume to which we do not 

 know the limit, it has hitherto always retained its 

 gaseous properties, and resumes its primitive volume 

 the instant the pressure is removed. 



If the particles approach sufficiently near to produce 

 equilibrium between the attractive and repulsive forces, 

 but not near enough to admit of any influence from 



