WHAT AIR IS. 157 



gen and nitrogen be the type, and, to popular ob- 

 servation, the example of air, yet air may mean 

 any thing, or all things; because all things, or 

 the elements of which all things are composed, 

 may exist in the state of air. 



The most accurate definition of air is, " matter 

 subdued by heat," so overcome by the tendency to 

 motion which heat imparts, that it has no cohesion, 

 and none of the common properties of matter, except- 

 ing gravitation the property which matter never 

 loses, or can lose, while it exists. No matter 

 what the substance be which is in the state of air : 

 be it hydrogen, which when in a state of air, is 

 the lightest of known substances, and on that ac- 

 count used for filling balloons, which, because of 

 their lightness, rise in the air and carry up men 

 and their instruments of observation; or be it gold 

 or platinum, which, when in the solid state, are the 

 heaviest of known substances, still if it be in the 

 state of air, all its properties, as solid or as liquid 

 matter, are subdued and suspended by heat, when 

 it is in the state of air, excepting gravitation or 

 weight. The direct action of that is also sus- 

 pended, and a heavy metal may, by being reduced 

 to the state of air or vapour, be made to float in 

 the atmosphere, and to pass upward rather than 

 downward. But that is owing to the dispersion 

 of the minute parts of it through much more space 

 than they occupied in the solid or the liquid form. 

 Could all those scattered particles be collected, 

 they would at all times weigh exactly the same ; and 

 if they were made again to occupy just the same 

 space as the solid or the liquid, all the properties of 

 the solid or the liquid would return, and it would 



