5 8 SCIENTIFIC AGRICULTURE. 



their constituents must be rendered soluble before 

 they can be taken up by the plant and used as food. 

 This change will take place gradually in the soil. 



130. In order to hasten the action of bones, it is 

 customary to convert them into what is known as 

 superphosphate. This is done by mixing .the 

 broken or ground bones with about half their weight 

 of common sulphuric acid, or oil of vitriol diluted 

 with two or three times its weight of water. After 

 the acid has acted upon the bones, a somewhat pasty 

 mass is formed, which may be mixed with ashes, saw- 

 dust, rich earth, refuse of salt-refineries, etc., to neu- 

 tralize excess of acid. 



131. The insoluble bone, or calcium phosphate, 

 is thus changed by the acid into a soluble phosphate, 

 commonly known as superphosphate. The sul- 

 phuric acid removes a portion of the calcium from 

 the bones forming calcium sulphate, or gypsum, 

 which is itself an excellent fertilizer. The addition 

 of ashes to neutralize excess of acid is an advantage 

 to the mixture, but unfortunately manufacturers or 

 dealers sometimes add sand and earth of no value, 

 in such quantities that suspicion has been cast upon 

 the genuineness of much of our commercial super- 

 phosphate. 



132. A large deposit of tricalcium, or bone phos- 

 phate, the remains of extinct animals, was discovered 

 near Charleston, South Carolina, some years ago. It 

 furnishes an abundant supply of this material, and 

 has caused a reduction in the cost of superphos- 



