184 ON THE FOOD OF PLANTS. 



I am convinced that by far the greatest 

 extent of injury, from what is placed to the 

 account of canker, mildew, &c. if correctly in- 

 vestigated, will prove to originate in the unwhole- 

 some supply, or impurity, of the food. 



As to the objection, that by leaving dung on 

 the surface, a too rapid decomposition of the 

 manure, will be followed by a too rapid con- 

 sumption of food ; it may be said, ** a man can- 

 not eat his cake and have it too.*' Let the crop 

 be suited to the manure, or the manure to the 

 crop, and as long as he gets its full value, he 

 will have little reason to complain of its coming 

 into his pocket too quick ; the sooner he gets 

 a profitable return for one dressing of dung, the 

 sooner he can afford another j and if a proper 

 course of crops be taken, he may go on a long 

 time, without feeling cause to complain that his 

 lands are too prolific, or too rich. 



To be consistent, we must either stick to 

 chemical principles, or give them up. The 

 difference in the effect of the method I re- 

 commend, of applying manure on the surface, 

 and there to suffer it to remain the longest pe- 

 riod convenient; and that, by Sir H. Davy, 

 of burying it immediately ; may be determined 

 by the comparative formation and effect of the 

 two gases, carbonic acid, and carburetted hy- 

 drogen. If the former be, as stated, a principal 



