AIR NOT A CHEMICAL COMPOUND. 211 



mical analysis cannot as yet render appreciable 

 the smallest essential difference between the hot 

 and dusty air of town, and the balmy breath- 

 ings of a country wind laden with the odour of 

 a thousand flowers. We shall have, on another 

 occasion, to show that a real difference does 

 always exist. 



Is air, then, a chemical compound, that its 

 constancy of composition is so remarkable? 

 Few in the present day appear disposed to con- 

 sider the constitution of the atmosphere in this 

 light. In fact, the admirable analyses of Dumas 

 and Boussingault have presented positive evi- 

 dence to the contrary, of the most incontro- 

 vertible character. But it is still sufficiently sin- 

 gular that the composition of the air is apparently 

 as constant and unvarying as if it were fixed by 

 the unchanging laws of chemical combination. 

 Air is therefore simply a mixture of gases, not 

 held together by the force of chemical union. 



The purely physical constitution of the air 

 was not ordained without a satisfactory object in 

 view. Whether we are sufficiently acquainted 

 with this subject to pronounce positively the 

 purposes for which it was thus ordained, may 

 be matter of question; but it is unquestionable 

 that a wise end was attained in its creation and 

 constitution upon simple physical principles, 

 and not upon the more complicated principles 



