358 Mr. Whelpley on the Idea of an Atom. 



velop each other,) and the force which developed p and w, was also 

 the force which put them in motion. 



Now, an atom left to itself, and related to itself only, and to 

 the parts of space, can have but one such axis of vibration. For, 

 if two such be developed, at any angle with each other, the mu- 

 tual repulsions p p\ n n' of the two, and their mutual attractions 

 p n\p' n, will cause them to coalesce in a common axis : In gen- 

 eral, if two axes be developed in a single atom, and at the same 

 instant, they will combine to form a third, according to laws of 

 the composition of forces. 



It follows, that an atom moving by itself, by reason of a com- 

 municated vibration, can move only in a straight line ; and this 

 is the line of inertial motion. 



Gravity. 



Gravity causes all bodies to vibrate in the line of attraction. 

 For, if one body be attracted by another, all parts of it are caused 

 to move at the same instant ; but the parts nearest to the attract- 

 ing body are more intensely affected than the more distant parts; 

 and the consequence will be, a slight separation among the parti- 

 cles of the attracted mass ; and the elastic return of the particles 

 will give rise to a vibratile motion of the whole mass. But sin- 

 gle atoms will be affected in the same manner with masses ; for 

 the nucleus of an atom has dimensions, and the nearer are more 

 intensely affected than the more distant parts. Gravity, there- 

 fore, may communicate the itiertial motion to an atom, causing 

 it to move in a straight line toward the cause of attraction ; and 

 though the cause of the first motion be removed, the vibration, 

 and consequently the rectilineal motion must continue. 



When two atoms of the kind described are present to each 

 other in space, they will excite or polarize each other. 



Let C and C be the nuclei of two gaseous atoms, 



C C 

 p ^ n p' . n' 



floating free in space, which they fill by their extension. If there 

 were only one such atonri, C would not be resolved into p n. If 

 there were two such, and their C's unresolved, they would have 

 no motion ; the attractions of the dissimilar forces, pn' p'n, would 

 balance the repulsions of the similar kinds, pp' nn'. But if the 

 resolutions of C and C have taken place in single axes, as repre- 



