LIME AND ITS USE. 37 



profusion in nature. It forms whole mountains, and 

 many soils are largely composed of it. The shell- 

 marls are almost pure ' 'carbonate of lime" (chalk), 

 as this combination of lime is named, and most soils 

 are abundantly supplied with it. Lime is indis- 

 pensable to the healthy growth of cultivated crops, 

 and where it is deficient, as in many peaty soils, 

 such crops must suffer unless lime is applied in 

 some form. It should also be remembered that the 

 natural formation of nitric acid in the soil (by the 

 conversion of nitrogenous matter, mysteriously but 

 conveniently called "nitrification"), is dependent on 

 the presence of lime, soda, or some other base. Sup- 

 pose we have a peaty soil unfit to produce good 

 crops on account of its acidity and deficiency of 

 lime. If we then apply fresh-burnt (caustic or 

 quick) lime, its very first action will be to combine 

 with and neutralize the free acids, and thus 

 sweeten the soil. Some of the new compounds are 

 often immediately utilized for plant food. The lime 

 also breaks up compounds in which potash, am- 

 monia and soda are held in an insoluble condition, 

 and makes these substances available for plant food. 

 It further hastens the decomposition of organic 

 matter in the soil and otherwise aids in furnishing 

 plants with the available compounds they desire. 



Lime is usually applied in the form of air-slacked 

 lime, marl or in other forms of carbonate of lime. 

 Peaty soils are often underlaid with a layer of marl 

 (generally almost pure carbonate of lime, which, 

 owing to the natural tendency of lime to sink in the 

 soil, has, in the course of centuries, been deposited 

 upon an impervious clay subsoil); hence such form 

 of lime is generally readily accessible for use on 

 these kinds of soil. Here it may directly afford 



