AERATION OF THE SAP. 35 



effects tend to its purification and to its remaining 

 adapted to the respiration of animals. Nearly 

 the whole of the carbon accumulated by vege- 

 tables is so much taken from the atmosphere, 

 which is the primary source from which they 

 derive that element. At the season of the year 

 when vegetation is most active, the days are 

 longer than the nights ; so that the diurnal pro- 

 cess of purification goes on for a greater number 

 of hours than the nocturnal process by which the 

 air is vitiated. 



The oxygen given out by plants, and the car- 

 bonic acid resulting from animal respiration, and 

 from the various processes of combustion, which 

 are going on in every part of the world, are 

 quickly spread through the atmosphere, not only 

 from the tendency of all gases to uniform diffu- 

 sion, but also from the action of the winds, which 

 are continually agitating the whole mass, and 

 promoting the thorough mingling of its different 

 portions, so as to render it perfectly homogeneous 

 in every region of the globe, and at every eleva- 

 tion above the surface. 



Thus are the two great organized kingdoms of 

 the creation made to co-operate in the execution 

 of the same design : each ministering to the 

 other, and preserving that due balance in the 

 constitution of the atmosphere, which adapts it 

 to the welfare and activity of every order of 

 beings, and which would soon be destroyed, 

 were the operations of any one of them to be 



