40 NATURAL FUTILITY. 



cent manures with soils, between wliich there would otherwise b$ 

 but little if *ny chemical attraction.* 



4th. Poor and acid soils cannot be improved durably, or profit- 

 ably, by putrescent manures, without previously malring such soils' 

 calcareous, and thereby correcting the natural defect in their con- 

 stitution. 



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 productiveness, and yield more profit, than any other 

 improvement practicable in lower Virginia. 



Dismissing from consideration, for the present, all the others, I 

 shall proceed to maintain the 



FIRST PROPOSITION. Soils naturally poor, and rich soils reduced 

 to poverty by cultivation, are essentially different in their poivcrs 

 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. 

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

 the amount of its earliest product, when first brought under cultiva- 

 tion, because 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 nu- 

 merous 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 excluded. . 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 manure. For these reasons, the degree of natural 

 fertility of any soil should be measured by its products after these 



* When any substance is mentioned as combining with one or more other 

 substances, as different manures with each other, or with soil, I mean that 

 a union is formed by chemical attraction, and not by simple mixture. Mix- 

 tures are made by mechanical means, and may be separated in like manner ; 

 but combinations are chemical, and require some stronger chemical attrac- 

 tion, to take away either of the bodies so united. 



When two substances 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 alkaline 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 constituent parts. 



