24 



CALCAREOUS MANURES— THEORY. 



detailed. The object of this essay will now be entered upon ; and what is 

 desired to be proved will be stated in a series of propositions, which will 

 now be presented at one view, and afterwards separately discussed in , 

 their proper order. 



Proposition 1. Soils naturally poor, and rich soils reduced to poverty by 

 cultivation, are essentially different in their powers of retaining putrescent 

 (or alimentary) manures ; and, under like circumstances, the fitness of 

 any soil to be enriched by these manures is in proportion to the degree of 

 its natural fertility. 



2d. The natural sterility of the soils of lower Virginia is caused by such 

 soils being destitute of calcareous earth, and their being injured by the pre- 

 sence and effects of vegetable acid. 



3d. The fertilizing effects of calcareous earth are chiefly produced by its 

 power of neutralizing acids, and of combining putrescent manures with 

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

 attraction.* 



4th. Poor and acid soils cannot be improved durably, or profitably, by pu- 

 trescent manures, without previously making such soils calcareous, and 

 thereby correcting the natural defect in their constitution. 



5th. Calcareous manures will give to our worst soils a power of retaining 

 putrescent manures, equal to that of the best— and will cause more produc- 

 tiveness, and yield more profit, than any other improvement practicable in 

 lower Virginia. 



Dismissing from consideration, for the present, all the others, I shall pro- 

 ceed to maintain the 



First Proposition. —Soils naturally poor, and rich soils reduced to poverty 

 by cultivation, are essentially different in their poiuers of retaining putres- 

 cent (or aliment a7-y) manures ; and, under like circumstances, the fitness of 

 any soil to be enriched by these manures is in proportion to the degree of 

 its natural fertility. 



The natural fertility of a soil is not intended to be estimated by the 

 amount of its earliest product, when first brought under cultivation, be- 

 cause several temporary causes then operate either to keep down or to 

 augment the product. If land be cultivated immediately after the trees are 

 cut down, the crop is greatly lessened by the numerous living roots, and 

 consequent bad tillage — by the excess of unrotted vegetable matter— and the 

 coldness of the soil, from which the rays of the sun had been so long ex- 

 cluded. On the other hand, if cultivation is delayed one or two years, the 

 leaves and other vegetable matters are rotted, and in the best state to sup- 

 ply food to plants, and are so abundant, that a far better crop will be raised 

 than could have been obtained before, or perhaps can be again, without ma- 

 nure. For these reasons, the degree of natural fertility of any soil should 



* When any substance is mentioned as combining w'lih one or more other substances, as 

 different manures with each other, or with soil. 1 mean that a union is formed by che- 

 mical attraction, and not by simple mixture. Mixlvres are made by mechanical means, 

 and may be separated in like manner; but combinailona are chemical, and require some 

 stronger chemical attraction, to take away either of the bodies so united. 



When two substancps combine, they both lose their previous peculiar qualities, or 

 neutralize them for each other, and form a third substance different from both. Thus, if 

 certain known proportions of muriatic acid and pure or caustic soda be brought together, 

 their strong attraction will cause them to combine immediately. The strong corrosive 

 acid quality of the one, and the equally peculiar alkahne taste and powers of the other, 

 will neutralize or entirely destroy each other— and the compound formed is common 

 table salt, the qualities of which are as strongly marked, but totally different from 

 those of either of -its constitutent parts. 



