42 TRUCK-FARMING AT THE SOUTH. 



vegetable matter, in all excrementitious matter, and in 

 the tissues and bones of animals. Bones consist of 

 phosphate of lime, or bone earth and gelatine. 



Phosphoric acid and lime unite in three different pro- 

 portions. In common bone earth there are three equiv- 

 alents of lime to one of phosphoric acid, and this salt of 

 lime is called the tricalcic phosphate, or three-lime phos- 

 phate. This is not soluble in pure rain water. Large 

 bones, as is well known, remain for ages buried in the 

 ground, and are only very slowly dissolved by the car- 

 bonic acid in the water. The next is the reverted, or 

 dicalcic, or two-lime phosphate, consisting of two equiv- 

 alents of lime to one of phosphoric acid, which is also 

 insoluble. The monocalcic, or one-lime phosphate, con- 

 sists of one equivalent of lime and one of phosphoric 

 acid, and is the acid-phosphate, or superphosphate of 

 lime of the agriculturist, and is soluble in water. 



The manufacturer is enabled to present this valuable 

 soluble fertilizer to agriculture by treating bones, or the 

 South Carolina phosphates, the poor phosphatic guanos, 

 the coprolites, or any other mineral tricalcic phosphate 

 of lime, with sulphuric acid, or oil of vitriol. This re- 

 moves two equivalents of lime (as plaster or sulphate of 

 lime), converting it into the one-lime, or superphosphate. 



The surest source of phosphoric acid is finely-powdered 

 bone meal. One ton of this contains, in its gela- 

 tine, as much nitogen as eight and one-half tons of 

 fresh stable manure, and twenty-three per cent, of it is 

 phosphoric acid. Bone meal is slowly soluble in the soil 

 by the action of carbonic acid. For vegetable growing it 

 should be decomposed in the manure pile, and supplied 

 at the rate of five hundred pounds to the acre. 



The manufacturer mixes finely-powdered fish-scrap, 

 nitrate of soda, or some other more or less nitrogenous 

 substance with his superphosphate, and produces his 

 "ammoniated superphosphate." This mere manipula- 



