ARTIFICIAL AND CONCENTRATED MANURES. 77 



in each, liill of corn, is still practised in regions near the 

 sea where they are easily procured. 



Leather Meal. — This material, already described in a 

 previous chapter, is frequently treated by various proces- 

 ses, in order to render its nitrogen more available. Chief 

 among these are heating to a high temperature, and steam- 

 ing, which change its original form and structure, making 

 it mealy and crumbly. Methods of treating with, borax 

 and benzine, and dissolving in sulphuric acid, are also 

 practised. Experiments have shown that all of these 

 processes aid materially in improving the quality of the 

 nitrogen in this product. 



Horn and Hoof Meal. — These materials are rich in 

 nitrogen, and are quite uniform in composition, though in 

 their original condition they are slow to decay. They 

 are frequently treated in somewhat the same manner as 

 leather, in order to render the constituent nitrogen more 

 directly available to plants. 



Thus, while these products, containing a high content of 

 nitrogen in very slowly available forms, do have some value, 

 it is doubtful whether their use, either in their original or 

 treated form, is advisable, except when they can be pur- 

 chased at a much lower price per pound than in forms 

 of known value. 



Cottonseed Meal. — A few vegetable waste products 

 contain sufficient nitrogen to warrant their use as concen- 

 trated manures. Among these cottonseed meal is probably 

 used to the greatest extent. The cottonseed is first hulled, 

 ground and steamed, and the oil extracted. It is quite 

 uniform in its composition, and contains on the average 

 six and eight-tenths per cent of nitrogen. Its value as 



