174 ON FALLOWING. 



Staggering even truth itselfi by a plausible theory, 

 when practical observation is not brought to aid 

 the judgment. 



To show the fallacy of the objections above 

 stated, and to prove that by the operation of 

 chemical principles, fallowing must add to the 

 fertility of the soil, we need only refer to what 

 has already been said on the nature of the food 

 of plants : however, the more clearly to establish 

 those principles which are most important, I 

 shall endeavour further to elucidate their appli- 

 cability. Admitting what Sir Humphry states 

 to be fact, " That the earths commonly found 

 " in soils cannot be combined with more oxygene, 

 " and none of them unite with azote j" yet the 

 remains of vegetables which are always in the soil 

 may ; superfluous or stagnant water may also be 

 dispersed ; and the formation of carburetted hy- 

 drogen gas prevented : for as he further says, "In 

 " the production of a plant from seed, some reser- 

 *' voir of nourishment is needed before the roots 

 " can supply sap, and this reservoir is the cotyle- 

 " don, in which itis stored up in an insoluble form, 

 *' and protected if necessary during the winter, 

 *' and rendered soluble by agents which are con- 

 *' stantly present on the surface. The change of 

 '* starch and coagulated mucilage intosugar, con- 

 " nected with the a})sorption of oxygene, may be 



