AIR 



AIR 



chief stay and support, that atten- 

 tion to their profession, the hold- 

 ing it in deserved respect, the re- 

 warding examples of successful 

 and peculiar industry in indivi- 

 duals must have an influence on 

 the advancement and progress of 

 the art. The spirit of emulation 

 is as capable of being excited in 

 this art, as in the calamitous, and 

 what we all acknowledge to be 

 the unprofitable one of War. A 

 farmer's breast is as open to ge- 

 nerous feelings, is as alive to ap- 

 plause and approbation, and as 

 much chilled by neglect, as that of 

 the proudest spirit that ever wore 

 a sword. Our defence then of 

 these exhibitions and these re- 

 wards, rests on the immutable laws 

 which regulate the human heart." 

 See Mass. Agr. Rep. vol. V. p. 85. 

 92. 215. 237. 374. 



AIR. Since the time in which 

 Mr. Deane wrote, great discove- 

 ries, relative to the constituent 

 parts, and essential qualities of at- 

 mospheric air have been made by 

 Scheele, Priestley, Lavoisier, Da- 

 vy and others. These celebrated 

 men have proved that its principal 

 elements are two gases, oxygen and 

 azote, or nitrogen ; and that it like- 

 wise contains small quantities of 

 aqueous vapour and of carbonic 

 acid gas ; and Lavoisier proved 

 that this last body is itself a com- 

 pound elastic fluid, consisting of 

 charcoal, dissolved in oxygen. 



Oxygen gas is necessary to 

 some functions of vegetables, as 

 well as indispensable to animal 

 life. If a seed germinates in con- 

 fined air, the oxygen, or a part of 

 it, is absorbed. The azote, or nitro- 

 gen remains unaltered. But as 

 vegetation proceeds in the open 



air, oxygen gas is given off, and 

 the carbon, or charcoal of car- 

 bonic acid gas, is absorbed, and 

 becomes a part of the organized 

 matter in the vegetable. 



The effects of nitrogen in vege- 

 tation are not exactly known. 

 It is ascertained, however, that 

 it prevents the oxygen from act- 

 ing with too much violence, and is, 

 perhaps absorbed by some vege- 

 tables. 



Carbonic acid gas combines 

 with many different bodies, and 

 furnishes vegetables and animals 

 with carbon or charcoal. When 

 a growing plant, the roots of which 

 are supplied with proper nourish- 

 ment, is exposed in the sunshine to 

 atmospheric air, containing its due 

 proportion of carbonic acid, the car- 

 bonic acid,after a time, is destroyed, 

 and a certain quantity of oxygen is 

 found in its place. " Carbonic acid 

 gas," says Sir Humphrey Davy, 

 " is formed in a variety of process- 

 es of fermentation and combus- 

 tion, and m the respiration of ani- 

 mals. And as yet no other pro- 

 cess is known in nature, by which 

 it can be consumed, except by ve- 

 getation. Animals produce a sub- 

 stance, which appears to be a ne- 

 cessary food of vegetables : vege- 

 tables evolve a principle necessa- 

 ry to the existence of animals ; 

 and these different classes of be- 

 ings seem to be thus connected to- 

 gether, in the exercise of their liv- 

 ing functions, and to a certain ex- 

 tent made to depend on each other 

 for their existence." 



Water, likewise always exists in 

 the atmosphere ; and the quantity 

 is greater or less in proportion to 

 the heal of the weather. When 

 the thermometer stands at 50^ of 



