180 ON FALLOWING. 



" clothing the surface were first ploughed in ;" 

 but how does this accord with his ideas on the 

 effects of paring and burning ? on the subject 

 of which, he very justly observes " Many ob- 

 " scure causes have been referred to for the pur- 

 " pose of explaining the effects of paring and 

 "burning; but, I believe, they may be referred 

 " entirely to the diminution of the coherence and 

 "tenacity of clays, and to the destruction of 

 "inert and useless vegetable matter, and its con- 

 * version into manure/' 



Ift then, the fertilizing effects of fire be wholly 

 comprised in its acting thus, as an alterative ; 

 how can it be denied, that the same effects, 

 though in a more moderate degree, are produced 

 by a summer fallow? Fire is undoubtedly a 

 powerful agent in fertilizing the land, and more 

 particularly when applied to stiff wet clays. 



In a general point of view, I agree with Sir 

 H. Davy, as to the effects of paring and burn- 

 ing, and in many of his ideas as to the peculiar 

 principles of its operation, and particularly when 

 he says, 



" When clay or tenacious soils are burnt, the 

 " effect is of the same kind ; they are brought 

 " nearer to a state analogous to that of sands." 



" In the manufacture of bricks, the general 

 " principle is well illustrated ; if a piece of dry 



