ASP MOUEIIX PHYSIC'S. 10*1 



apart. It has no parts or dimensions; it is a mere 

 geometrical point without extension in space; it has 

 not tho property of impenetrability, for two atoms 

 can, it is supposed, exist at the same point. 



In modern molecular science according to 

 Maxwell, " we begin by assuming that bodies are 

 made up of parts each of which is capable of motion, 

 and that these parts act on each other in a manner 

 consistent with the principle of the conservation of 

 energy. In making these assumptions we arc 

 justified by the facts that bodies may be divided into 

 smaller parts, and that all bodies with which we are 

 acquainted arc conservative systems, which would not 

 be the case unless their parts were also conservative 

 systems. 



" We may also assume that these small parts are in 

 motion. This is the most general assumption we can 

 make, for it includes as a particular case the theory 

 that the small parts arc at rest. The phenomena of 

 the diffusion of gases and liquids through each other 

 show that there maybe a motion of the small parts of 

 a body which is not perceptible to us. 



" We make no assumption with respect to the 

 nature of the small parts whether they are all of 

 one magnitude. We do not even assume them to 

 have extension and figure. Each of them must be 

 measured by its mass, and any two of them must, 

 like visible bodies, have tho power of acting on one 

 another when they come near enough to do so. The 

 properties of tho body or medium are determined by 

 the configuration of its parts." 



These small particles are called molecules, and a 



