374 now CROPS peed. 



point of remuneration, but the sterility thu5 induced is of 

 a kind that easily yields to rest or other meliorating agen- 

 cies, and is far from resembling in its permanence that 

 which depends upon original poverty of constitution. 



Significance of the Absorptive Quality.— Disintegration 

 and nitrificntion would lead to a waste of the resources 

 of fertility, were it not for the conserving effect of those 

 physical absorptions and chemical combinations and re- 

 placements which have been described. The two least 

 abundant ash-ingredients, viz., potash and phosphoric acid, 

 if liberated by the weathering of the soil in the form of 

 phosphate of potash, Avould suffer speedy removal did not 

 the soil itself fix them both in combinations, which are at 

 once so soluble that, while tliey best serve as plant-food, 

 they cannot ordinarily accumulate in quantities destruct- 

 ive to vegetation, and so insoluble that the rain-fall cannot 

 wash them off into the ocean. 



The salts that are abundant in springs, rivers, and seas, 

 are naturally enough those for which the soil has the least 

 retention, viz., nitrates, carbonates, sulphates, and hydro- 

 chlorates of lime and soda. 



The constituents of these salts are either required by 

 vegetation in but small quantities as is the case with chlo- 

 rine and soda, or they are generally speaking, abundant 

 or abundantly formed in the soil, so that their removal 

 does not immediately threaten the loss of productiveness. 

 In fact, these more abundant matters aid in putting into 

 circulation the scarcer and less soluble ingredients of 

 crops, in accordance with the general law established by 

 the researches of Way, Eichhorn, and others, to the effect 

 that any base brought into the soil in form of a freely sol- 

 uble salt, enters somewhat into nearly insoluble combina- 

 tion and liberates a corresponding quantity of other bases. 



" The great beneficent law regulating these absorptions 

 appears to admit of the following expression : those bodies 

 which are most rare and ^vecious to the (proving plant art 



