290 AMERICAN HUSBANDRY. 



Pure calcareous earth or lime ... 30 parts, or 33 

 Sulphuric acid 32 " 43 



Crystallized water ... 38 " 24 



100 100 



It requires from 450 to 500 times its weight of 

 water to dissolve it. When pure, it does not effer- 

 vesce with acids ; it is insipid in taste, and free from 

 smell. A simple mode of trying its quality consists 

 in putting a quantity of it pulverized into a dry pot 

 over the fire, and when heated it gives out a sul- 

 phurous smell. If the ebullition or bubbling which 

 then takes place be considerable, the plaster is good ; 

 but if not, it is considered indifferent ; and if it re- 

 main motionless, like sand, it is not thought to be 

 worth anything. Its colour is white, gray, or blue. 

 Its effects in benefiting agriculture have been great- 

 est in Germany and in the United States. Its bene- 

 fits in Great Britain and France have been less ob- 

 vious. 



The soils upon which gypsum operates most beneficial 

 ly are the light, dry, sandy, and gravelly. Upo.n 

 soils containing little or no vegetable matter, its ef- 

 fect is trifling r but when these lands are dressed 

 with dung, the gypsum then produces a great effect ; 

 and, the dung being present, the poorer the land, the 

 greater its benefits. It seldom produces any sensi- 

 ble effect upon wet grounds, and frequently none 

 upon stiff clays. 



The crops which are most benefited by gypsum are 

 the clovers, lucerne, Indian corn, and pease. There 

 are some few cases noticed of its being found ben- 

 eficial to wheat and other small grains ; but it is the 

 generally received opinion that it does not operate 

 directly on these. Gypsum, however, may be made 

 indirectly beneficial to all crops which are grown 

 upon a clover lay, by causing a greater growth of 

 clover, which becomes food for the crop which fol- 

 lows, and which is abundant in proportion to the 



