812 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



netism, chemical attraction, cohesion, or polar crystalline force, 

 adhesion, elasticity, etc., are identical in their nature and origin 

 with the force exhibited in the motions of masses of matter, being 

 the manifestations of universal force acting separately upon atoms 

 or molecules, instead of collectively upon their aggregations. 



JUtractions and I'ejjuhwns have no real existence as inherent 

 properties of matter. Atoms or masses of matter have no power 

 to act upon each other across vacant spaces. Their apparent 

 attractions and repulsions are the dj^namical effects of primarily 

 external force, which has become associated by mutual intercep- 

 tions producing resultant gravitations. The terms attraction and 

 repulsion are, therefore, to be understood to signify effects i\nd 

 not causes. 



Heat, the principal repulsive force of nature, is the momentum 

 or centrifugal force of atoms in their paths or orbits about each 

 other. The measure of its quantity in a given body, as a positive 

 force is the'aggregate momentum of the atoms of that body, modi- 

 fied by their angular velocity. 



The temperature of a body is the mean or average momentum of 

 its atoms, and it has a uniform temperature when the mean momen- 

 tum of all the atoms is equal. If, however, in practical problems 

 the sensible energy or power of performing tvoi^/c is to be con- 

 sidered, its proper measure will be, as in the case of masses, the 

 total vis viva or living force, similarly modified. 



Since, from its essential nature, force can never be directly 

 recognized by the senses, we perceive its existence only by its 

 effects when associated with matter. Of these, gravitation points 

 more directly and obviously than any other to the independent 

 existence of its cause. Most other phenomena seem capable of 

 explanation by supposing a transfcrrence of the force, which is 

 already associated with one body, to another, by contact. 



Contact, indeed, is the only way, apparent to the senses, by 

 which such a transfer of force takes place. If, therefore, our con- 

 ceptions are to be limited by one direct sensation, fx plenum would 

 seem indispensable for explaining the transmission of forces across 

 the celestial and inter-atomic spaces. A careful investigation of 

 this sul)ject, however, with a strict adherence to the simple defini- 

 tions of force and matter, already given, will j^robably lead most 

 minds to the conclusion that no transfer of force ever takes place 

 by the actual contact of bodies, or their component atoms ; and 

 indeed, that no actual transfer takes place at all, the apparent trans- 



