248 SOILS AND MANURES 



the case of meat meals, to which they are closely ana- 

 logous, the composition depends largely upon the amount 

 of bony matter they contain. 



The Norwegian product is made chiefly from cod, and 

 contains from 7 to 10 per cent, of nitrogen, and from 

 12 to 14 per cent, of phosphates. The American fish 

 guano is made from herrings ; it contains about the same 

 proportion of nitrogen, but is generally poorer in phos- 

 phates. 



The fertilising ingredients are insoluble and only be- 

 come available as the substance is oxidised. The large 

 amount of oil naturally present in the fish hinders decom- 

 position, and retards the action of the manure. The bulk 

 of the fatty matter is, however, generally extracted in the 

 course of manufacture, but purchasers of fish manure 

 should obtain a guarantee that it contains not more than 

 3 per cent, of oil. The percentages of phosphates and 

 nitrogen should, of course, also be guaranteed. Like meat 

 meals they are mainly nitrogenous manures, and give their 

 best results on the lighter class of soils. 



