87 



tinous matter of the bone and constitute one of tlie most 

 common forms of partial manures of this class. 



The boiled or de-gelatinized bone, obtained as a by-product 

 of gelatine manufacture, is sometimes found on the market, 

 but this, of course, contains only phosphoric acid. 



Tankage, a product of the large slaughter houses, consists 

 chiefly of a mixture of the dessicated residues of meat and 

 bone left from the treatment of the slaughter house wastes 

 for extraction of grease. The proportions of meat and bone 

 in this fertilizer vary considerably, and lead to quite large 

 differences in the nitrogen and phosphoric acid contents of 

 different samples, the phosphoric acid generally being in 

 excess, though its proportion is dependent largely upon the 

 amount of bone in the material. 



Fish scrap, which is simply the dry, pulverized residue 

 from the extraction of oil from fish, contains both phos- 

 phoric acid and nitrogen, though the latter predominates 

 and the product is chiefly used for the nitrogen which it 

 supplies. The fertilizing value of all the materials of this 

 class is largely enhanced by a finely divided condition of the 

 particles, and a mechanical analysis is frequently resorted 

 to in addition to the chemical examination. 



(5.) MANURES CONTAINING PHOSPHORIC ACID AND POTASH. 



Many of the acid phosphates upon the southern market 

 have been mixed with a small proportion of kainite or some 

 of the higher grade potash salts, and are thus better adapted 

 for composting than the plain super-phosphates. By the 

 simple mixture of goods of this class with cotton seed meal 

 a complete fertilizer is obtained, and the farmer can fre- 

 quently prepare advantageously, in this way, mixtures to 

 meet the needs of his difl^erent crops. 



(6) MANURES CONTAINING NITROGEN AND POTASH. 



Nitrate of potash is the only manure of importance of 

 this class, supplying both potash and nitrogen in a very 



