38 GAEDEXING FOR THE SOUTH. 



but in the greatest abundance in the juices of those plants 

 we use for the table. (Liebig.) 



This sulphur is obtained from the sulphates naturally 

 contained in or applied to the soil, especially from gypsum, 

 or sulphate of lime. Gypsum, it is believed, acts in two 

 ways, being sparingly soluble in water; it acts directly 

 as food for plants, supplying them with sulphur and lime, 

 and indirectly, by its action on the volatile carbonate of 

 ammonia which it unites with and fixes. When they meet 

 in solution, a double action takes place ; both substances 

 are decomposed, and their elements unite in the forms of 

 carbonate of lime and sulphate of ammonia. The latter salt 

 is not volatile, and the ammonia is thus retained in the 

 soil for the use of the crops. Gypsum is very beneficial 

 to green crops, as the cabbage, potato, also to maize, and 

 especially to clover, peas, and other leguminous crops. 

 (Lindley?) A bushel of it has been known to yield an 

 extra ton of clover hay to the acre when applied broad- 

 cast. Gypsum is very useful to sprinkle on manure heaps 

 and upon the contents of privies, to fix the ammonia con- 

 tained therein. 



Sulphur alone may sometimes be used to advantage as 

 a manure. It is not soluble in water, but when finely di- 

 vided, it will slowly unite with the oxygen of the air. 



Sulphur is destructive to most insects, and found very 

 serviceable to sprinkle about green-houses and vineries for 

 the prevention of mildew. 



Chlorine. In districts remote from the sea, the chlo- 

 rides of sodium, calcium, and magnesia, when applied to 

 the soil, are useful to vegetation. These compounds are 

 frequently found in the sap of plants. As nearly all soils 

 contain more or less of common salt, the application of 

 any chloride is seldom absolutely essential, but is fre- 

 quently very serviceable, especially to certain crops. 



Chemistry has endeavored to ascertain by analyzing 

 the ashes of plants whh;h of these substances is most im- 



