iS SCIENTIFIC AGRICULTURE. 



stances, and in this way carries food to the roots of 

 plants (8). All natural waters, such as are found in 

 springs, wells, rivers, and lakes, contain in solution 

 more or less mineral matter derived from the soil. 

 Rain-water is the purest, as it contains nothing in 

 solution except what it gets from the air as it falls 

 through it. 



26. Nitrogen is found in the atmosphere in 

 large quantity, and also in plants and animals. It 

 forms four-fifths of the volume of the air. The most 

 convenient way to prepare nitrogen is to remove the 

 oxygen from air by means of phosphorus (9). Other 

 substances can also be used for the removal of the 

 oxygen. 



27. Nitrogen is a colorless gas with no taste or 

 smell. It neither burns nor dpes it support combus- 

 tion. Animals cannot live in it, and yet it is not 

 poisonous. It has no power to sustain life, merely 

 serving in the atmosphere to dilute the oxygen. The 

 three gases just mentioned are easily distinguished 

 by means of a lighted taper. Oxygen will not burn, 

 but will make the taper burn with great brilliancy ; 

 hydrogen will put out the taper, but will burn itself 

 with a pale-blue flame; nitrogen will neither burn 

 nor will it support the flame, but put it out at once. 



28. Ammonia is a very important compound of 

 nitrogen and hydrogen. It is formed when am- 

 monium chloride (sometimes called sal-ammoniac) 

 is rubbed with common lime, and is a gas of strong, 

 pungent odor (10). It unites with acids, destroying 



