MANURE FROM ANIMAL WASTE. 265 



To do this the Hqaor formed by the condensation of the steam is 

 run otf through/. It holds a Uttle dissolved horn in solution ; then 

 the lower manhole i is opened and the horn withdrawn. When 

 properly boiled, the horn is softened through and through and forms 

 an elastic mass, like rubber. It is dried in a dryer, and then forms 

 a black pliable vitreous mass which is crushed in a bone crusher ; 

 that is the way ground horn of commerce is obtained. In the pure 

 state, it has a greenish or greyish-yellow^ colour, and contains 13 to 

 15 per cent of nitrogen. Other analogous materials are treated 

 along w^ith the horn. Horn shavings, w^ool waste, etc., occupy 

 a great volume, and it would take a very large-sized boiler to treat 

 them apart, that is why they are mixed with horn to fill the empty 

 spaces between the large pieces, at the risk even of slightly diminish- 

 ing the percentage of nitrogen in the product. The condensed w^ater 

 (horn liquor) contains 1 to 2 per cent of nitrogen ; it thus has a 

 certain value, but as its treatment would be costly it is best to add 

 it in the manufacture of bone dust. Attempts were made to let it 

 putrefy, and then distil it to recover the ammonia, but this method 

 was soon abandoned. The steaming of horns has many drawbacks. 

 It expends much fuel and labour, and a loss of nitrogen in the 

 condensed water. Finally, the w^ork injures the health of the w^ork- 

 men. There is in fact disengaged from horn during the digestion 

 a very volatile organic substance, which strongly attacks the 

 mucous membranes, especially the workmen engaged in emptying 

 the digester and who consequently have to come in contact with 

 the steamed horns, but up to now nothing has been found to 

 replace this method, because ground horn rendered soluble by steam 

 is of much greater agricultural value than raw horn. It has been 

 seen that the horn dissolves partially in the water condensed from 

 the steam, and that without decomposition it so far proves that it 

 passes to the soluble condition at least partially. Ground horn 

 thus rendered soluble possesses a great absorbent capacity for 

 Av.iter, whilst ground raw horn repels water, and cannot be moistened, 

 and as putrefastion requires the help of water, it follows that the 

 soluble horn will deco npose more easily, and produce a more rapid 

 and more sure fertilizing action than raw horn. From the preced- 

 ing, it follows that the use as inanures of powdered horn and wool 

 dust w^hich have not been treated by steam should be abandoned, for 

 in the raw state these materials cannot be crushed to the requisite 

 degree of fineness for the rational application of concentrated 

 chemical mcl^Qures. 



Leather Waste. — Tanners' and curriers' waste can be bought 

 cheap when they are unfit for glue manufacture ; their nitrogen 

 content is very variable, even w^hen not affected by moisture or 

 sand. Thus sole leather in the pure state and perfectly dry often 

 only contains 4 to 5 per cent of nitrogen. The cutting and waste 

 of new^ leather from saddlers' and shoemakers' shops have a higher 



