236 CONSERVATIVE ORGANS. [LECT. V. 



notice, with regard to dung, that when it is com- 

 pletely rotten it does not afford much soluble 

 carbon, owing to its having become as it were ox- 

 ydized and the carbon being converted into a real 

 charcoal ; other principles also, such as carbonic 

 acid and ammonia, useful both as stimuli and nu- 

 triment to plants, are dissipated during the violent 

 fermentation, which is requisite to reduce dung 

 into this state. Fresh dung, or that which is not 

 completely rotten, on the contrary, benefits not 

 only the present crop but several subsequent ones, 

 as its good effect continues as long as the process 

 of decomposition goes on. That many of the good 

 effects of fresh dung depend on the extrication of 

 heat is evident ; and I am inclined to think it 

 is to this agent, chiefly, that must be attributed 

 the great superiority of the green vegetable matter 

 used as manure, in some experiments detailed by 

 Mr. Knight, in the Horticultural Transactions * ; 

 and not, as that gentleman supposes, to the nutri- 

 ment of vegetables being more easily assimilated 

 into the substance of the living plant, the less it 

 has passed from the state of living vegetable 

 matter. 



Such are some of the facts relative to soils, 



epidermis of the Equisetum, Mare's Tail, that it is used by 

 cabinet-makers for polishing furniture : and it is also found 

 composing part of the epidermis of Wheat, Oats, and some 

 other grasses. 



* Vide Volume 1st. 



