CALCAREOUS MANURES-THE014Y. 57 



all this former ingredient of tlie soil in general, on the surface. This 

 process must have the effect, in the course of time, of fixing on and near 

 the surface the whole of a scanty supply of lime, and of leaving the sub-soil 

 without any. But if there is within the reach of the roots more lime than 

 any one crop or growth of plants needs, then the superfluous lime will be 

 permitted to remain in the sub-soil, which sub-soil will then be improvable 

 by vegetable substances, and readily convertible to productive soil. The 

 manner in which lime thus operates will be explained in the next chapter. 

 Nearly all the wood-land now remaining in lower Virginia, and also much 

 of the land which has long been arable, is rendered unproductive by 

 acidity, and successive generations have toiled on such land, almost with- 

 out remuneration, and without suspecting that their worst virgin land was 

 then richer than their manured lots appear to be. The cultivator 

 of such soil, who knows not its peculiar disease, has no other prospect 

 than a gradual decrease of his always scanty crops. But if the evil is 

 once understood, and the means of its removal is within his reach, he 

 has reason to rejoice that his soil was so constituted as to be preserved 

 from the effects of the improvidence of his forefathers, who would have 

 worn out any land not almost indestructible. The presence of acid, by 

 restraining the productive powers of the soil, has in a great measure 

 saved it from exhaustion ; and after a course of cropping which would 

 have utterly ruined soils much better constituted, the powers of our 

 acid land remain not greatly impaired, though dormant, and ready to be 

 called into action by merely being relieved of its acid quality. A few crops 

 will reduce a new acid field to so low a rate of product, that it scarcely 

 will pay for its cultivation ; but no great change is afterwards caused, by 

 continuing scourging tillage and grazing, for fifty years longer. Thus our 

 acid soils have two remarkable and opposite qualities, both proceeding from 

 the same cause : they can neither be enriched by manure, nor impoverished by 

 cultivation, to any great extent. Qualities so remarkable deserve all our 

 powers of investigation ; yet their very frequency seems to have caused 

 them to be overlooked ; and our writers on agriculture have continued to 

 urge those who seek improvement to apply precepts drawn from English 

 authors, to soils which are totally difTerent from all those for which their 

 instructions were intended. 



CHAPTER VIII. 



THE MODE OP OPERATION BV WHICH CALCAREOUS EARTH INCREASES THE FERTILI- 

 TY AND PRODUCTIVENESS OF SOILS. 



Proposition 3. The fertilizing effects of calcareous earth are chiefly pro- 

 duced by its power of neutralizing acids, and of combining putrescent ma- 

 nures with soils, between which there would otherwise be but little, if any, 

 chemical attraction. 



Proposition 4. Poor and acid soils cannot be improved durably, or profitably, 

 by putrescent manures, witlioict previously making them calcareous, and 

 thereby correcting the defect in their constitution. 



It has already been made evident that the presence of calcareous earth 

 in a natural soil causes great and durable fertility. But it still remains to 

 be determined, to what properties of this earth its peculiar fertilizing effects 

 are to be attributed. 



