OF AGRICULTURE. 213 



on such soils, and then limed. The farmer will find 

 his grain crops greatly increased, and his land left in 

 better heart. 



Quick- lime should never be used with "guano," 

 stable or fermenting manures; it has the effect of 

 setting the ammonia free in these manures. After 

 the lime has been sometime on the surface of the 

 soil, it can exercise no injurious effect on any kind of 

 manure. 



The most valuable kind of lime for agricultural 

 purposes, is that obtained from burning oyster shells, 

 and allowing it to remain exposed to the air a few 

 hours to slack. The amount used to the acre, depends 

 upon the nature of the soil, from thirty to one hun- 

 dred bushels; thirty bushels on the light, and one 

 hundred on the clay lands. 



GYPSUM SULPHATE OF LIME, OR PLASTER. 



Gypsum, or the sulphate of lime, is a well known 

 white, crystalline compound, found in large deposits, 

 in various parts of the world. The native plaster, 

 or gypsum, of commerce, consists of: 



Water 21 per cent. 



Lime 33 " 



Sulphuric acid 46 " 



100 parts. 



A ton of pure plaster will yield when ground, about 

 twenty-five bushels. Dr. Benj. Franklin, when he 

 wished to introduce this fertilizer into America from 

 France, in order to convince his countrymen of its 

 efficacy, sowed in large letters upon a clover lot, at 

 Washington city, in powdered plaster, this phrase: 

 " This land has been Plastered. 1 ' The effect of this 

 application of plaster was distinctly visible for several 

 years. 



