6 NATURAL THEOLOGY. 



recovers a great degree of its purity.^ Here then 

 again, allowing for the scale upon which nature 

 works, we see the salutary effects of storms and 

 tempests. The yesty waves which confound the 

 heaven and the sea, are doing the very thing 

 which was done in the bottle. Nothing can be of 

 greater importance to the living creation, than the 

 salubrity of their atmosphere. It ought to recon- 

 cile us, therefore, to these agitations of the ele- 

 ments, of which we sometimes deplore the conse- 



ces3 of vegetation, that the uniformity of the air's composition is 

 maintained universally. 



The union in which the oxygenous and nitrogenous portions of 

 the atmosphere exist, also merits attention. It is ascertained to 

 be of a peculiar kind ; for it is not merely that of mechanical ad- 

 mixture, —the union of aggregation, — inasmuch as the nitrogen 

 gas, being about a seventh part Ughter than the oxygen, would 

 rise to the top, and so make the air of higher elevations more pure, 

 contrary to the fact. , Nor is it hke most other chemical unions, 

 inasmuch as it is both extremely feeble, and is formed without any 

 diminution in the bulk of the two substances combined together. 

 But the kind of union in which tlie two gases are held is produc- 

 tive of the most beneficial effects. Their disengagement from 

 each other is so easily accomplished, that there is the greatest fa- 

 cility in supporting flame and respiration ; while their mixture is 

 so perfect, that the mischiefs are prevented which would arise from 

 their being exhibited either to the lungs or to heated bodies in their 

 pure state. 



* That agitation with water will remove certain impurities in the 

 air is undeniable, but not all impurities. Animals by breathing 

 consume the oxygen, leaving carbonic acid gas and nitrogen gas. 

 Water absorbs the former easily, and bulk for bulk ; but of the lat- 

 ter it will only absorb 1^ per cent. So of the products of putre- 

 faction, (beside carbonic acid,) carburettcd hydrogen, and sulphu- 

 retted hydrogen gases, water will absorb of the latter bulk for 

 bulk ; but not above If per cent of the former. 



