74 FERTILISERS CONTAINING NITROGEN [chap. 



afford a definite idea of the quality of a shoddy, some 

 opinion can be formed by tearing a small sample to 

 pieces and trying each portion in a gas or candle flame. 

 Wool, silk, hair, and all nitrogenous materials, frizzle 

 up and burn slowly with an unpleasant smell ; cotton, 

 linen, and similar substances of no fertilising value, burn 

 quickly with a clear flame, since they consist when pure 

 of cellulose. Or the mass may be digested by gentle 

 heating with a strong solution of caustic soda or potash, 

 in which the wool and kindred substances will dissolve, 

 leaving untouched the cellulose and dirt. But analysis 

 forms the only real basis for determining the richness of 

 the material, added to which the farmer must exercise his 

 own judgment about its fineness and the possibility of 

 getting it properly distributed throughout the soil. 



Woollen shoddies are sometimes treated with 

 sulphuric acid, with a view of starting the decomposi- 

 tion of the nitrogen compounds and so rendering them 

 more quickly available. Shoddy thus treated is also 

 used as a source of nitrogen in making various com- 

 pound and mixed manures. Evidence is, however, 

 lacking that the sulphuric acid does quicken the decay 

 of the shoddy, and on any soils but those rich in calcium 

 carbonate the introduction of so much free sulphuric 

 acid is not advisable. 



It would be difficult to enumerate all the bodies 

 which from time to time get applied to the land as 

 nitrogenous manures : tallow chandlers' waste or 

 " greaves " is a residue containing from 3 to 9 per 

 cent, of nitrogen, according to its origin, and a little 

 phosphoric acid ; it is often, however, comparatively 

 high in price, because the better qualities are saleable as 

 poultry food. 



Spent hops, and kiln or malt dust (the rootlets of 

 the germinated barley which are broken off when the 



