SCIENTIFIC AGRICULTURE. 103 



only in one proportion, forming lime. The equivalent number 

 of calcium is 20.5. 



Lime is the most important and abundant of all the earths, 

 being extensively distributed through the mineral kingdom, 

 and constituting the principal earthy ingredient in the shells 

 and bones of animals, and also existing in all plants. It is 

 found in nature combined with carbonic acid, as in marble, 

 limestone and chalk, in quantities so large as to form entire 

 mountains. It is found combined with sulphuric acid, consti- 

 tuting gypsum or plaster of paris: it is also combined with 

 phosphoric, fluoric and arsenic acids. 



The minerals, calcareous spar, gypseous spar, arragonite, and 

 many others, are composed of lime. All natural waters con- 

 tain more or less of this earth. Lime is a pure, white, alkaline 

 earth: when burned lime is exposed to the air, it rapidly 

 absorbs water, and falls into a line powder, which is called 

 "slaked lime," or hydrate of lime. This earth has a strong 

 affinity for acids, with which it forms several salts. It is only 

 sparingly soluble in water, and less so in hot than in cold 

 water : when completely dissolved in clear water, it is called 

 lime water: this, when exposed to the air, unites with the 

 carbonic acid of the air, and a thin pellicle or layer of carbon- 

 ate of lime is formed on the surface, this soon falls to the 

 bottom, and another layer is formed ; and so the process con- 

 tinues until the lime ail becomes a carbonate, and is thus 

 precipitated from the water. 



Lime attacks and destroys both animal tissues and vegetable 

 substances with rapidity, and without the exhalation of those 

 noxious gases and offensive odors, which result when putre- 

 faction goes on without the presence of lime. Lime is valua- 

 ble as a manure in soils destitute of this earth, by supplying 

 an indispensable element to plants, and also by neutralizing 

 r.cidity, dissolving silica, and decomposing insoluble organic 



