Newton, Leibnitz, and Boscovich to the Atomic Theory. .57 



they may still hold on their radiant course, the centres or nuclei from 

 which they emanate must tend to retreat from eacli other ; for the law 

 of assimilation implies a continuity of force between the advancing front 

 of an undula and the centre whence it issued, and therefore a state 

 of tension in the atomosphere in that direction in which the undula is 

 proceeding analogous to rigidity. 



Of Heat. 

 IV. But such a mode of action in the atoms or molecules consti- 

 tuting a sensible mass, must be productive of a sensible phenomenon. 

 The mass must expand or increase in volume, and that to an extent 

 and under modifications determined by the atomic or molecular struc- 

 ture of the mass expanding. Here, then, we have a phenomenon, 

 which, so far as appears, answers to lieat. Its further considera- 

 tion must, however, be deferred till we become acquainted with specific 

 molecular structures. It may be merely added here, that accord- 

 ing to this view there is good ground and reason on both sides to 

 affirm now that heat is only motion, and now that it is due to a special 

 agent, caloric ; for when any attempts have been made to define caloric, 

 it has generally been described in much tlie same terms as the 

 atmosphere or atomosphere around the nuclei here. It may, indeed, be 

 said, that this insulative atomosphere, which, according to the views here 

 advanced, constitutes all the volume of every atom and molecule, ought 

 rather to be named electricity than caloric, as will presently appear. 

 But this were a dispute about names merely. The atomosphere is, 

 according to what is here advanced, the common ground both by calorific 

 and electric action, and both of these are purely modes of motion not 

 only convertible into each other, but into such motion as is palpable 

 to the senses, and commonly goes by the name. 



Or Polarity. 



V. From the Law of Assimilation, however (operating as inertia, 

 and demanding symmetry, as will appear hereafter), it follows that these 

 systems of undula; emanating from the centres 

 and nuclei of atoms and molecules, must ever 

 tend to form themselves into sustained cur- 

 rents in the atomospheres of these atoms and 

 molecules — currents in which the successive 

 undulae shall chase each other continuously 

 in the line which is at once the most recti- 

 linear and that of least resistance. And thus, 

 as another function of the heat, which must 



Vol. IV.— No. 1. i 



