REFUSE MATTERS. 307 



organic matters containing nitrogen, which exist in 

 crude sugar ; and wool, soap, an abundant refuse 

 from the wool-mills, consisting of putrid urine, in 

 which the wool is boiled to remove the grease which 

 it naturally contains, and which is consequently rich 

 in ammonia. 



817. Strong animal manures are doubly valuable; 

 for not only do they contain abundance of those 

 matters which constitute the food of plants, but they 

 also assist in rendering useful materials which would 

 without them be of far less service. Whether these 

 manures are employed in the liquid or in the solid 

 form, some means should be adopted to retain the 

 ammonia, either by the addition of acids or by some 

 other method. (7»8). 



818. These remarks are far less applicable to 

 animal manures, such as fatty substances, horn, wool, 

 bones, &c., which change but slowly. These sub- 

 stances for the most part act slowly and gradually, 

 and in a very different manner from the softer parts 

 of animals. 



819. In general, the strength of animal manures 

 is in proportion to the quantity of nitrogen which 

 they contain ; those which contain much of that ele- 

 ment decompose rapidly, and evolve a considerable 

 quantity of ammoriia, whilst those containing little or 

 no nitrogen change slowly, and, though valuable, and 

 perhaps more lasting in their effects as manures, are 

 far less powerful for the time. 



820. Woollen rags, hair, feathers, clippings of horn 

 and skin, greaves, the refuse of the tallow-melters, the 



