THE ATMOSPHERE. 13 



this vast theatre of nature, gentle, uniform, and constant, 

 at the same time, that it does not destroy or impair the 

 power of the agent which conducts them. 



This abundant and harmless portion of the atmo- 

 sphere does not, like its more enterprising neighbor, 

 infuse itself into nearly every mass of matter in the three 

 great kingdoms of nature, but, besides forming more 

 than four fifths of the aerial ocean which surrounds the 

 earth, it constitutes a considerable part of all animal 

 substances, though less than oxigen. 



It is not found, in any quantities, either in the vegeta- 

 ble or mineral kingdom, of both of which oxigen constitutes 

 a large part. 



Chemists have generally considered the two substances 

 already spoken of, as the essential ingredients of the at- 

 mosphere. Several others are, however, always found in 

 it, and if they are not concerned in its more important 

 operations, they fill many minor offices in contributing to 

 the endless and constant wants of the innumerable beings 

 living and acting upon the earth. 



Such is carbonic acid, or fixed air. This gas, which 

 is nearly twice as heavy as common air, is found to exist, 

 at all times, in every region of the atmosphere, from the 

 lowest ravine or cave, to the top of the highest mountain. 

 Except in caves, wells, and some other low places, where 

 carbonic acid settles from its great weight, it is never 

 found in the atmosphere except in small quantities, some 

 say a hundredth part, some a thousandth, but probably 

 variable, existing in larger quantities, at some times, and 

 in some places, than others. 



Although this substance is fortunately never found in 

 the atmosphere except in small quantities, it frequently 

 takes an important part in promoting the happiness, and 

 producing the disasters of mankind. It is supposed to 

 be an important agent in the process of vegetation ; veg- 

 etables having the power of extracting it from the air 

 and converting it to their own sustenance and growth. 

 While the whole animal kingdom are constantly inhaling 

 or consuming oxigen, and at the same time throwing off 

 carbonic acid, the vegetable kingdom are inhaling or 

 absorbing carbonic acid, and, a part of the time at least. 



VOL. i. NO. r. 2 



