62 FIRST PRINCIPLES OF AGRICULTURE. 



other products mentioned, because the leather has passed 

 through a process, the very purpose of which was to make 

 it less liable to decay. 



The purchase of these materials is only advisable when 

 they can be procured very cheaply. Their application is 

 useful when the object is gradual increase in fertility, 

 rather than immediate increase in crop. Hair wastes 

 have been found advantageous in the growing of ber- 

 ries, hops, and other slow-growing crops, while wool and 

 leather have materially improved meadows and perma- 

 nent pastures. The nitrogen in these materials is im- 

 proved in form, and made more quickly available, when 

 composted with manure. 



Wood- Ashes. Of the potassic manures, unleashed 

 wood-ashes are the most useful. The pure ashes from 

 the different varieties of wood vary in composition ; as 

 a rule, the softer woods contain less, and the hard woods 

 more, potash, the range being from sixteen to forty per 

 cent. 



Ashes also contain lime in large amounts, while phos- 

 phoric acid is contained in much smaller quantities. 

 Wood-ashes, as usually gathered for market, however, con- 

 tain very considerable portions of moisture, dirt, etc., 

 which cause a variability in composition not due to the 

 character of the woods from which they are derived. 

 The average analysis of commercial wood-ashes shows 

 them to contain less than six per cent of potash, two 

 per cent of phosphoric acid, and thirty-two per cent of 

 lime. Leached wood-ashes contain on the average thirty 

 per cent of moisture, one and one-tenth per cent of pot- 

 ash, one and one-half per cent of phosphoric acid, and 

 twenty-nine per cent of lime. 



