FARMER'S ASSISTANT. 



A. 



AIR. Seeds which are buried so deep as to be seclud- 

 ed from their requisite portion of air will not vegetate; for 

 this reason, weeds are constantly springing up in new 

 ploughed grounds ; those seeds which before lay too deep 

 for vegetation being turned up nigher the surface. 



Let seeds be sown in the glass receiver of an airpump, 

 exhausted of air, and they will not vegetate; but admit the 

 air arid they will grow directly. 



The lodging, or falling, of some kinds of grain and of 

 grass, is owing to standing too thick to admit a free circu- 

 lation of ajr, by means of which they can only preserve a 

 healthy state. Plant one grain of wheat, for instance, in 

 the richest soil, and the stalks when grown will not fail; but 

 plant a great number of grains in the same soil, so closely 

 together as to preclude a free circulation of air amongst 

 the stalks, and they become unable to sustain their owa 

 weight. 



Air consists of different gases, as they are termed; the 

 oxygene gas, or vital air, which is essential to the existence 

 of all animals ; the hydrogene gas, or inflammable air ; the 

 nitrogene gas, or common atmospheric air, deprived* of its 

 oxygene, by having served the purposes of respiration or 

 combustion, and which is also called azote; and the carbo* 

 me acid, formerly called fixed air, so often found fatal in 

 the bottoms of wells and elsewhere. These are the princi- 

 pal ; but by the application of a sufficient degree of 'caloric 

 (heat) all liquid substances can be changed into the gase- 

 ous state. 



The common atmosphere is principally composed of the 

 oxygene and nitrogene gases, being about twenty-one pans 

 of the former and seventy-nine of the latter, 



As the oxygene or respirable air is essential to the exist- 

 ence of animals; so the hydrogene and the azote is absorb- 

 ed in plants, and is essential to their growth. Plants also, 

 while exposed to the light, emit oxygene. Thus, by the 



B 



