72 THE CULTURE OF FARM CROPS. 



rapidity and luxuriance, but it appears to exercise a con- 

 siderable control over the functions of vegetable life. In 

 this regard there are several special properties of this com- 

 pound which should be clearly understood, by the farmer 

 and student of agriculture. 



First. It has a powerful affinity for acid substances, and 

 unites with them with great facility as it escapes into the 

 atmosphere, or meets with them in the soil. Hence when 

 formed or liberated in the stables; in the cattle yard; man- 

 ure and compost heaps and in other places where organic 

 matter is in a process of decay; it unites with such acid sub- 

 stances and forms salts or saline compounds. And these 

 salts appear to exert a considerable influence upon the growth 

 of crops. 



Second. This affinity for acid substances however, is 

 much less active and strong than that possessed by other al- 

 kaline compounds, as potash, lime, soda and magnesia. 

 Hence if any one of these alkaline substances is brought in- 

 to contact with a salt of ammonia, this is at once decom- 

 posed and its acid is taken up by the stronger alkali, while 

 the ammonia is separated and set free in its gaseous state. 

 If a small quantity of sal-ammoniac (chloride of ammon- 

 ium) is powdered and is mixed with twice its weight of 

 powdered quicklime, the ammoniacal gas is liberated, and 

 the chlorine unites with the lime. This is one of the several 

 methods o"f procuring pure ammonia, and is an instance of 

 one of the very many useful functions performed by lime in 

 the soil for the benefit of farm crops; especially upon lands 

 which have been made rich in organic matter by liberal 

 manuring, or which are naturally well supplied with decay- 

 ing vegetable matter, as reclaimed swamps or peat bogs. 

 It also shows the injurious effect of mixing lime with man- 

 ure of any kind in which ammonia exists, or can be devel- 

 oped by the decomposing agency of the lime, unless at the 

 same time, the lime is used in moderate quantity and a con- 

 siderable amount of soil or other matters which absorb am- 

 monia are used to counteract this result of the lime. 



Third. The salts and saline compounds which are formed 



