CH. VIIl] 



Bone Manures 



141 



Bone meal. The bones intended for this purpose are 

 then crushed and sorted into half inch bones, quarter 

 inch bones and bone meal. 



Steamed bone flour. The bones intended for glue, and 

 the ends of the cutlery bones, are crushed and again 

 steamed but this time at a higher pressure (50 lbs.), 

 when most of the nitrogenous constituents are extracted 

 as gelatine or glue. The residue can now be got into a very 

 fine state of division and is sold as steamed bone flour. 



Dissolved or vitriolised bones. These are made by 

 treating bones with sufficient sulphuric acid to dissolve 

 about half of the phosphate. The product is usually 

 somewhat sticky, and has not the finish of a well-made 

 superphosphate. The following table gives the com- 

 position of various bone manures, but as the material 

 is very variable the figures are to be considered as 

 approximate only. Raw bones are still used in the Wolds 

 of Yorkshire and in certain other districts but not 

 generally elsewhere. 



Bone meal usually acts best on soil rich in humus or 

 soils lacking in lime; it is not very satisfactory on cal- 

 careous soils. At Rothamsted it gave good returns for 

 spring wheat, barley and swedes, and also at Saxmmid- 

 ham, but in the Cockle Park^ and Aberdeen experiments 



Cockle Park Bull. No. 37, Davy Houses Field; Aberdeen Bull. No. 3. 



