ON THE FOOD OF PLANTS. 153 



being either overlooked, or considered unim- 

 portant : but in this, I think, they egregioiisly 

 err. 



It is certain, that when animal and vegetable 

 substances are left to spontaneous decay, the 

 putrefactive fermentation must be the ultimate 

 result; but it is demonstrative, that the resi- 

 duum, or the matter left by completely putrefied 

 animal and vegetable substances ; will not sup- 

 port the vegetables cultivated by man, in a 

 healthful progress to prolificacy, any moi'e than 

 either of the simple earths : and that when 

 reduced to this state, its action is merely me- 

 chanical, or operative only, as it serves to temper, 

 or constitute, the compost or soil. And further, 

 that when in too great a proportion, in this state, 

 it is injurious, as it retains water until it becomes 

 in a state of stagnation ; whilst, on the contrary, 

 every process that checks the putrefactive fer- 

 mentation, and every operation that retards and 

 dispels its effects, in and on the soil ; and the 

 addition of many substances that are decidedly 

 anti-putrescent, such as charcoal, alkaline salts, 

 lime, &c. and which facilitate the dispersion of 

 water : add to the fertility of the soil, and in- 

 crease its prolificacy. 



Thus we find that the spreading of dung 

 thinly over, and near, the surface of the earth j 



