BY SALINE MANURES. 



319 



be applied to the soil, 100 lbs. to the acre, with the most per- 

 fect confidence in its utility. The former contains carbon- 

 ate of lime, about half of its weight, with carbonate of soda. 

 The ashes from antharcite coal contain carbonate of lime, al- 

 umina and oxide of iron, and are useful saline manures. 

 Ashes of all kinds are particularly useful on grass lands. 

 Peat ashes contain so much gypsum that they generally act 

 with greater power than those from wood. 



II. Salts whose add does not enter into the composition of 

 plants, and which is poisonous. This division includes, 1. 

 Sulphates, such as sulphate of lime, iron, potash and soda. 

 2. Muriates or chlorides, as common salt, chloride of calcium, 

 and of potassum. 



1. Sulphate of lime, or plaster, has long been used as a sa- 

 line manure. It has been proved by experiment, that " a 

 bushel of plaster per acre, or even the one four-hundreth part 

 of one per cent, produces effects on alluvial land, which shows 

 its good results, as far as the eye can reach." This effect 

 can be explained : on the supposition that plants decom- 

 pose the salt, and let loose the lime upon the geine ; the acid 

 must act upon the silicates, and form sulphates of potash, of 

 soda, and (if silicate of lime exist) of lime. In this way the 

 plaster reproduces itself. 



Plaster has been found in some plants. It is supposed by 

 Liebig, to act chiefly by condensing ammonia, and retaining 

 it for the wants of vegetation. 



Sulphate of iron, or copperas, is not applied to any but a 

 calcareous soil, and the result is the formation of gypsum, 

 by the action of lime to decompose the copperas. 



2. Chlorides. Common salt is beneficial upon some soils ; 

 it acts by the soda which it contains. Thirty bushels to the 

 acre, has produced good effects. It may be best employed 

 for composts. 



Spent lye from soap-works has already been considered. 

 In all cases, the action of salts depends upon the presence 



