PHOSPHATIC MANURES 137 



where one has a difficulty in deciding which 

 of these two manures to use alone. 



The two substances just described are the 

 most important of the purely phosphatic 

 manures. A third, namely, Precipitated 

 Phosphate, has given an excellent account 

 of itself in field trials, but home supplies seem 

 to be so firmly held for export to Japan, 

 Honolulu, the Mauritius, etc., that little is 

 available for the British farmer. It is 

 chiefly a bye-product in the manufacture of 

 gelatine, glue, and similar substances from 

 bones, the phosphate of which is rendered 

 soluble by acid and subsequently precipitated 

 by the addition of lime. Raw Mineral 

 Phosphate, too, ground to a fine powder, 

 has been employed with fair success on 

 sour meadows, but the bulk of this substance 

 is not used as manure till it has been made 

 into superphosphate. Bone Ash, again a 

 substance imported from South America, 

 where bones are often used as fuel supplies 

 little but phosphate, and, when ground up, 

 a certain amount comes on the market as 

 manure. 



The valuation of phosphatic manures may 

 proceed on one or other of the lines indicated 

 when dealing with nitrogenous manures. 

 On the Continent the system adopted is to 



