160 PROPERTIES OF AIR. 



substance) is in a state of air, it is literally, and in 

 the truest sense of the word, a material a material 

 which the plastic hand of nature can mould and 

 fashion into any new production for which it is 

 adapted, with far more ease and certainty than the 

 potter can out of the same clay mould " one vessel 

 for honour, and another for dishonour," or the 

 builder can apply the same bricks as part either of a 

 palace or a pigsty. 



This, when we think seriously of it, is really the 

 most wonderful part of the whole wide field of 

 nature ; and it is the one in which the foundations 

 of all our knowledge of nature's working are laid. 

 The solvent power of heat, which loosens the firm 

 cohesion of the diamond with as much ease and 

 certainty as it melts ice into water, or the sunbeams 

 into all those tints of colour that enliven the face of 

 nature, overcomes all, but destroys or injures nothing. 

 It holds all matter captive ; but the captivity is only 

 that the purposes of matter may thereby be fulfilled ; 

 for the moment that the proper ingredients of any 

 compound come together in due proportion, and 

 under the requisite circumstances, the heat which 

 held their properties suspended lets them slip, and 

 they instantly act, and the compound is formed, with 

 the same ease and the same certainty as if it had 

 existed from the beginning. 



Not only that, but the heat is as powerful in es- 

 caping away, and allowing the qualities of materials, 

 which it had held in the state of air, to act, in the 

 formation of new substances, as it is in the suspen- 

 sion of those properties, in bringing about the 

 destruction of that which is old, that which has 

 already served the purpose of its being, and is occu- 

 pying materials to no use. 



Oxygen and hydrogen, the component parts of 

 water, can both be obtained in the state of pure and 

 colourless air, the first a little heavier, at the same 

 temperature, than the common air of the atmosphere, 



