SULPHATE OF LIME. 103 



has txK) frequently arisen from the presence of 

 this earth in the native soil itself, where con- 

 sequently its application could do no good; 

 and a more urgent argument for the necessity 

 of a knowledge of chemistry to the agricul- 

 turist, than is furnished by this simple fact, 

 which has occurred more than once in the his- 

 tory of this manure, cannot be cited. 



The action of this earth, gypsum, in pro- 

 ducing such luxuriant effects on grasses arises 

 entirely from its power of absorbing the am- 

 monia of the atmosphere (page 60,) which im- 

 portant article by its solution in water and sub- 

 sequent absorption by the spongelets is thus 

 yielded to the plant itself. 



The ammonia existing in rain water is, when- 

 ever it comes in contact with gypsum, at once 

 absorbed, and a new compound is formed called 

 sulphate of ammonia. In this state the am- 

 monia is fixed, that is, it has no volatile pro- 

 perties, and water is the only thing needed to 

 dissolve this new compound for the use of 

 vegetation, and the absence of moisture will fre- 

 quently explain why gypsum produces either 

 a less effect or no difference at all in dry fields 

 or meadows. The lime disengaged by this 

 action is either dissolved with the sulphate of 

 ammonia and absorbed by the roots, or it com- 

 bines with other gases to form carbonate or ni- 

 trate of lime. 



In order to give some idea of the effect to be 

 produced by gypsum, it may be stated* that 



* Liebig. 



