OF AIR. 159 



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 sun- 

 beams into all those tints of colour that enliven the 

 face of nature, overcomes all, but destroys or in- 

 jures 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 to- 

 gether in due proportion, and under the requisite 

 circumstances, the heat, which held their proper- 

 ties 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 

 escaping away, and allowing the qualities of ma- 

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

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

 suspension 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 

 occupying 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, and the second a great deal lighter. 

 Each, in its separate state, may have a great va- 

 riety of temperatures, and have its volume aug- 

 mented by heat or the removal of pressure, or 

 diminished by pressure or by cold ; and though 

 that has not yet been satisfactorily done by human 

 experiment, there is not the least doubt, that by 

 p 2 



