314 SAWDUST. 



energetic that the value of manure is seriously in- 

 jured, by the high temperature to which it is thus 

 exposed. 



846. The decay of some vegetable manures may 

 be facilitated by the addition of lime ; for the objec- 

 tion which applies to the mixture of lime with animal 

 manures is not applicable to the ordinary vegetable 

 manures. The latter for the most part contain but 

 little nitrogen, their value principally depending on 

 their mechanical action, and on the formation of 

 carbonic acid. 



847. Vegetable manures decay more or less rapidly 

 in proportion to the quantity of nitrogen which they 

 contain ; green manures contain a notable quantity 

 of gluten and albumen, and accordingly decompose 

 rapidly, whilst sawdust, which consists principally 

 of woody fibre, and contains hardly any nitrogen, 

 decomposes slowly. Sawdust is, therefore, a most 

 excellent substance to mix with the excrement of 

 animals, and other strong animal manures. 



848. Wood sawdust is valuable as manure in pro- 

 portion to the facility with which it decomposes, and 

 the inorganic matters which it contains; that obtained 

 from young trees decomposes with more facility than 

 the sawdust of old wood. 



849. The wood of those trees which contain much 

 resinous matter decays less rapidly than other woods, 

 and is therefore not so valuable as a constituent of 

 mixed manures (802). Those woods which, when 

 burnt, yield a large quantity of ashes rich in alkaline 



