OF JIOULD. 17 



manures during the various stages of their decompositions 

 by giving rise to the formation of products very somble. 



M. de Saussure found, that mould which had been de- 

 prived of its extract, contained a little more carbon, than 

 that which had not been so deprived ; the former yielded 

 33^, the latter 31. 



One hundred parts of the dry extract of turf mould 

 furnished 14 parts of ashes, which, when leached with 

 boiling water, afford -^^^^ = ^jj of salts composed of pure 

 potash, muriates, and alkaline sulphates. 



It is necessary to observe, that when mould is reduced 

 to ashes, the action which water exercises upon it is in 

 inverse proportion to the power of the heat td which it 

 has been subjected ; if that have been very intense, a sort 

 of semi-vitrification takes place, which unites the earthy 

 principles with the alkaline salts, and renders the mass 

 less soluble in water. M. de Saussure has proved, that 

 boiling water cannot extract at most more than yf ^ =i -^^ 

 of the salts contained in the ashes of mould ; whilst after 

 having obtained ^\y in alkaline salts from the dry extract 

 of mould, by the aid of boiling water, he procured by 

 another analytical process, a quantity of salts equal to the 

 first. 



With the exception of the earthy and saline principles 

 contained in mould, in the proportion of 5 to 7, all the 

 other principles are entirely destructible by the action of 

 air and water. 



When mould is exposed to the action of air, or entirely 

 immersed in water, it suffers no decomposition ; but when 

 it is brought into contact with the atmosphere, or with 

 oxygen gas, after having imbibed water, the oxygen com- 

 bines with the carbon of the mould, and produces a vol- 

 ume of carbonic acid gas, always equal in volume to the 

 quantity of water imbibed ; when this winter is sufficiently 

 impregnated with carbonic acid, the volume of air en- 

 closed under a bell glass, in contact with the mould, 

 suffers no further change. 



The carbon of which the mould is deprived by its union 

 with oxygen, is not in proportion to the loss occasioned 

 by decomposition ; it still disengages carburetted hydro- 

 gen and water, which proves the combination of oxygen 

 with hydrogen, and of the last with carbon. The decom- 

 position of mould is very slow, and even when aided bv 

 3* 



