MANURE. 159 



of cow dung, while, if we regard the salts only, 

 100 lbs. of bone dust, contain nearly 66 times as 

 much as an equal weight of cow dung. Such 

 statements while they express the chemical facts, 

 are almost, if not quite, supported by the testimony 

 of those who have, in practical agriculture, applied 

 these concentrated animal manures. It is a com- 

 mon opinion, that bones from the soap-boiler have 

 lost a large portion of their animal matter. It is er- 

 roneous. Boiling, except under high pressure, ex- 

 tracts very little of the gelatine, and not all the fat 

 and marrow. Heads and shoulder-blades and the 

 smaller bones still contain, after boiling, 3 1-2 per 

 cent, of fat and tallow. If the phosphate of lime 

 of such bones is dissolved out by acid, the animal 

 portion remains, with all the form and bulk of the 

 bone. Bones which are offered in the market, are 

 quite as rich in the elements above stated, as are 

 unboiled bones. The phosphate of lime is render- 

 ed quite soluble by its combination with gelatine and 

 albumen. The class of mixed manures, containing 

 nitrogen, has thus been considered. The principle 

 of their action and the foundation of their value, 

 pointed out. The action of the second class, or 

 those not containing nitrogen, remains to be ex^ 

 plained. 



