154 



results of an experiment made by Mr* Robertson 

 of Madras : 



The action exercised by gypsum upon the soil 

 has not yet been sufficiently ascertained, it being 

 of a very complicated nature. But we have every 

 reason to believe that its chemical properties of 

 absorbing ammonia, and disengaging magnesia and 

 potash from their insoluble combinations, are the 

 chief agencies to which we must attribute the 

 undeniable improvement of the soil which follows 

 a judicious application of this manure. Gypsum 

 should always be powdered previous to use, which 

 can be very easily effected by half-burning the 

 gypsum, as the tenacious nature of the natural 

 crystals is thus destroyed. 



The refuse of soda-water manufactories, consist- 

 ing of sulphate of lime, is one of the cheapest 

 sources of this manure, and, on account of its fine 

 state of division, preferable to native gypsum. 



Nitrate of potash, the sora khar of the native of 

 India, is a manurial agent procurable all over the 

 country, and, though commanding a high price, 



