PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 813 



fer being due to a continually equal and opposite, though varying 

 disturbance of the rays of universal force, producing the effect 

 called action and reaction. 



A comet will approach the sun from infinite space, pass around 

 it, and then recede from it in the opposite direction, without any 

 transfer of force taking place. Nor is there any logical or mecha- 

 nical absurdity, if we accept the definition already given, in con- 

 ceiving that two atoms may gravitate directly to each other, and 

 even pass through the same portions, or through each other, with- 

 out the occurrence of a transfer of force. 



It is true that this could not take place if the atoms w^ere as 

 described by Newton, "solid, massy, impenetrable, movable par- 

 ticles, so hard as never to wear or break ; " but this view is not 

 only discordant with inductive reasoning, based upon modern dis- 

 coveries in physical science, but leads to logical absurdities, and 

 apparently meets with little favor among the more eminent modern 

 physicists. 



hnpenetrahility will, therefore, be considered not as a property 

 of individual atoms, but as a manifestation of the force associated 

 with aggregated atoms, by ■which the approach of one aggregation 

 or body to another, involving the intermingling of their respective 

 atoms, or their occupancy of a smaller space, is powerfully resisted, 

 and beyond certain limits rendered i^ractically impossible. 



Chemistry and optics teach us that the atoms of any homogenous 

 substance are uniform in the amount of their inertia throughout 

 the visible universe. By the laws of mechanics, two isolated 

 atoms, acted upon by gravitation, will move about each other in 

 one of the forms of conic sections. 



If the atoms are entirely free from lateral motion they will move 

 in a rigid line, passing through both, in which case the secant 

 plane becomes tangent to the cone. 



The nature of the motion in this path M'ill depend upon the 

 amount of associated force. If this be less than the maximum of 

 gravitating force which they are able to accumulate in each other, 

 in other words, less than that they would acquire l)y falling 

 together from infinite space, then a constant vibration will result, 

 the atoms approaching with accelerated velocity, passing through 

 each other, and then receding with retarded velocity to a distance 

 which is a measure of the living force of the atoms. 



If the force at contact is exactly equal to this maximum or 

 potential of gravity, if we may so call it, the atoms will, after con- 



