PRACTICAL AGRICULTURE. 47" 



action of water. But they become warm when reduced 

 to a fine powder : and moistened bones generate heat, 

 and enter into putrefaction ; the gelatine which they 

 contain is decomposed, and its nitrogen converted into 

 carbonate of ammonia, and other ammoniacal salts, 

 which are retained, in a great measure, by the powder 

 itself. Bones burnt till quite white, and recently heated 

 to redness, will absorb seven times their volume of am- 

 moniacal gas. The analysis of borje enables us to say, 

 that while 100 pounds of bone dusl add to the soil 33 

 of gelatine, the organized substance of horn, or as much 

 organized matter as is contained in 300 or 400 pounds 

 of blood or flesh, they add, at the ^ame time, more than 

 half their weight of inorganic matter, lime, magnesia, 

 soda, common salt, and phosphoric acid, in combination 

 with some of these — all of which, as we have seen, must 

 be present in a fertile soil, since the plants require a 

 certain supply of them all at every period of their growth, 

 but more especially during the maturation of the straw 

 and grain. These substances — like the inorganic mat- 

 ter of plants ploughed into the soil — may, and do exert 

 a beneficial agency upon vegetation after all the orga- 

 nized structure of such decaying plants is broken up 

 and destroyed. One hundred parts of dry bones contain 

 33 per cent, of dry gelatine, and are equivalent to 250 

 parts of recent human urine. We do not speak now of 

 the bone-dust which remains after all the animal gela- 

 tine is removed, in boiling them to extract size for the 

 calico-printer. 



Horn is a still more powerful manure than bone : that 

 is to say, it contains a greater proportion of organized 

 animal matter. The peculiarity is, that horn, hair, and 

 wool, as organized substances, are dry ; while blood 

 and flesh contain from 80 to 90 per cent, their weight 

 of water. Hence, a ton of horn-shavings, of hair, or of 

 dry woollen rags, ought to enrich the soil with as much 

 animal matter (and consequently nitrogen,) as would be 

 yielded by ten tons of blood. In consequence of this 

 dryness, horn and wool decompose more slowly than 

 blood ; and hence, the effect of soft animal matters is 



