320 LIME. 



of anj such manures, is wholly dependent on the 

 nature and composition of the soil. 



869. When reading accounts of experiments with 

 various inorganic manures, it must always be borne 

 in mind that on one soil salts of potash, on another 

 nitrate of soda, and on a third phosphate of lime, 

 may be the best manure, because the soil happens to 

 be deficient in alkaline salts or phosphates. 



870. Plants almost invariably contain salts of the 

 alkalies, and lime, or magnesia ; sometimes combined 

 with organic acids, sometimes with sulphuric, muriatic, 

 or phosphoric acid. Phosphates of lime and mag- 

 nesia, in particular, are very commonly 'met with in 

 plants. It will be proper to enumerate briefly the 

 artificial sources of these inorganic substances, and 

 to consider the best method of supplying them to the 

 soil. 



871. Lime is a very common ingredient in plants, 

 and is also found in almost all fertile sails ; the ad- 

 dition of lime or calcareous matter, therefore, to soils 

 which are destitute of it, or contain but very little, in- 

 variably improves them. Lime is added to the soil 

 pure, in the form of quick and slaked lime ; as a car- 

 bonate in the various forms of chalk, limestone, marl, 

 shell-sand ; as a sulphate in gypsum and plaster- 

 stone ; and as a phosphate, in bones, native phos- 

 phates, and the various organic manures already 

 referred to. 



872. When quicklime is spread over the surface 

 of land, other effects arc produced besides the mere 



