considered as the Results of Vibratory Motion. 343 



the phenomena of heat by the theory of vibratory motions), 

 although losing heat by degrees, preserves, however, more 

 than the parts to which it is communicating heat. Hence an 

 objection arises against the theory of the transmission of heat 

 by vibratory motion*. 



In a note inserted in 1832 in the 49th volume of the Biblio- 

 theque Universelle of Geneva, page 225, I endeavoured to 

 answer this objection by showing from which sort of motion 

 arise the phaenomena of which I have spoken. I intend now 

 again to make public my ideas upon the subject, and adding 

 to them some more extended developments. 



The principle I have announced rests on the distinction I 

 established long since between particles, molecules, and atoms. 

 I call a particle an infinitely small part of a body of the same 

 nature with it, so that a particle of a solid body is solid, a 

 particle of a liquid body liquid, and of a gas aeriform. 



Particles are composed of molecules held at a distance 

 from each other; first, by what at that distance remains of the 

 attractive and repulsive forces proper to the atoms ; 2ndly, by 

 the repulsion established between them by the vibratory mo- 

 tion of the interposed aether ; 3rdly, by attraction in the di- 

 rect ratio of the masses, and in the inverse ratio of the square 

 of the distances. The term molecules I give to an assemblage 

 of atoms held at a distance from each other by the attractive 

 and repulsive forces proper to every atom, forces which I ad- 

 mit to be so superior to the preceding that those may be con- 

 sidered relatively as almost insensible. What I call atoms, 

 are the material points from which these attractive and re- 

 pulsive forces emanate. 



From this definition of molecules and atoms it follows that 

 the molecule is essentially solid, whether the body to which it 

 belongs be solid, liquid, or gaseous ; that the molecules have 

 necessarily the form of a polyhedron, of which the atoms, 

 or a certain number of them at least, occupy the summits. 

 These polyhedral forms are those called by crystal lographers 

 primitive forms. 



I admit that in the transition of bodies from the liquid to the 

 gaseous state, and reciprocally, the molecules in passing from 

 one of these states of equilibrium between forces which deter- 

 mine their distance, to another state of equilibrium between 

 the same forces, merely recede from or approach one another ; 

 but I think that in passing from the liquid to the solid state, two 



* However, as a body exposed to the rays of the sun is heated at first 

 on that part on which the rays fall, and that heat is gradually trans- 

 mitted to the remainder, it is impossible to admit that the light and heat 

 of the solar rays consist in vibrations, without admitting also that the heat 

 transmitted in the interior of a body is equally produced by vibratory 

 motions. 



