184 ON MANURE. 



The substances applicable as manure ought to be arranged 

 according to the products desired. The alkalies are peculiarly 

 necessary for the production of vegetable constituents destitute 

 of nitrogen, such as sugar, starch, pectin, and gum ; phosphates 

 are peculiarly valuable for the formation of the constituents of 

 the blood. A field richlv treated with animal manure, and 

 therefore with phosphates, produces a barley which is rejected 

 by the brewer of beer, because it is too rich in the constituents 

 of the blood, and proportionally poor in starch. Hence, the 

 very ingredient which is of the highest value to the feeders of 

 stock, is held in low estimation by the brewer ; because the 

 object of the first is to produce flesh, the object of the latter is 

 the fabrication of alcohol. 



Fresh bones, wool, hair, rags, hoofs, and horn, are manures 

 containing nitrogen as well as phosphates, and are consequently 

 fit to aid the process of vegetable life. 



One hundred parts of dry bones contain from 32 to 33 per 

 cent, of dry gelatine ; now, supposing this to contain the same 

 quantity of nitrogen as aniraal glue — viz. 5*28 per cent., then 

 100 parts of bones must be considered as equivalent, to 250 parts 

 of human urine. 



Bones may be preserved for thousands of years, in dry, or 

 even in moist soils, provided the access of air is prevented ; as is 

 exemplified by the bones of antediluvian animals found in loam 

 or gypsum, the interior parts being protected by the exterior 

 from the action of water. But they become warm when reduced 

 to a fine powder, and moistened bones generate heat and enter 

 into putrefaction ; the gelatine is decomposed, and its nitrogen 

 is converted into carbonate of ammonia and other ammoniacal 

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

 itself.* 



Charcoal, in a state of powder, must be considered as a very 

 powerful means of promoting the growth of plants on heavy 

 soils, and particularly on such as consist of argillaceous earth. 



Ingenhouss proposed dilute sulphuric acid as a means of in. 



* Bones burnt till quite white, and recently heated to redness, absorb 

 7*5 times their volume of pure ammoniacal gas. 



