136 NATURAL MANURES. VI. 



Large quantities of bones are obtained from towns and 

 they are now imported from America and Africa. They are 

 slow in action and their effect upon a soil often extends over 

 several years. In order to render their action more rapid they 

 are often converted into superphosphate or " dissolved bones," 

 which will be described hereafter. 



Bone ash is imported from South America ; it of course is a 

 purely mineral manure, the organic matter having been re- 

 moved. Occasionally bones are fermented by moistening 

 them with urine and leaving them exposed to the air. 



The following analyses will show the composition of various 

 commercial products from bones : 



Haw Fermented . Bone 



bones. Bones. b ' ash. 



Water ... ... 11-06 12-02 7'00 6'70 



Organic matter ... 30'48 28- 71 20'00 



Calcium phosphate 50-69 49-28 64-00 73-52 



Calcium carbonates] x.r\% \ 7-30 \ 



and undetermined j 1 8 9 2 ;- 1 09 



Alkali salts ... ... 2-25 j 0'70 j 



Sand 0-50 1-07 2-00 9-69 



100-00 100-00 100-00 100-00 

 Nitrogen ... 3-61 3-47 2-5 



Another product from bones is " bone black," used in de- 

 colourising liquids, e.g., sugar syrup; this consists of about 

 10% finely divided carbon, mingled with the mineral con- 

 stituents of bone, often containing 75 80% calcium phos- 

 phate. It is made by heating bones in closed retorts, and 

 after it is so clogged with colouring substances as to be 

 useless for decolourising purposes it is used under the name 

 of " spent char" as a manure, especially as it then contains 

 a small quantity of nitrogen. 



Meat meal or meat guano. This is the dried refuse, with 

 bones, from the manufacture of " extract of meat," &c., re- 

 duced to fine powder. A similar product is obtained by drying 

 the offal from slaughter-houses, &c., also, in Germany par- 

 ticularly, by drying the carcasses of horses or cattle that have 



