Vital Physics. 43 



drawn, is nothing. It will be said that cold is a term 

 applied only to temperature, and, as heat or repulsive force 

 is withdrawn, so cold becomes manifest, or is there. Quite 

 so, but the attractive force is stronger as the repellent 

 force diminishes. This is a perversion, it is said ; attraction 

 belongs to all particles, and is their state of natural inertia, 

 but, when heat is given, motion begins, and the natural 

 inertia is overcome by the force of repulsion, or caloric. 

 Put it anyhow, the more attraction acts upon particles in 

 the mass, the more are they in a state of inertia and nothing- 

 ness. Next, in astronomy, the more the repulsion shows 

 itself, either by its distance or velocity, the more it proves 

 inertia ; and the more the attractive force acts, as when 

 three bodies are in one line, as sun, moon, and earth, so 

 much the more evidence is there that a real force is in 

 action, and not inertia in the slightest, for the inertia plays 

 its cards all the other way,* and has a tendency to fall out- 

 wards from the line of the orbit, and that in a most 

 determined manner, without the aid of any force saving the 

 inexhaustible impetus in the line of its tangent, which was 

 first given to it by a gentle tap " Now go about your busi- 

 ness." No one who has carefully examined the nature 

 of the planetary motions can for one moment doubt the 

 sufficiency of the explanation of motion by attraction pro- 

 ceeding from the sun as a centre, and that it thoroughly 

 explains the orbital motion of the planets and satellites, if 

 the preliminary proposition be granted, that the tangental 

 force, once started, is incapable of being brought to com- 

 position and resolution by continuous deflections from the 

 straight line, by the action of the attractive force. 

 That a planet, running in an orbit, obeys the order of increase 



* It must be borne in mind, in speaking of cold and heat in relation 

 to physics, that there is no reference to these conditions as applied to 

 sensation. 



