CALCAREOUS MANURES-THEORY. 53 



benefit obtained. Much greater effects on the texture of soils are derived 

 from much less quantities of calcareous earth, besides obtaining the more 

 valuable operation of its other powers. 



Every substance that is open enough for air to enter, and the particles of 

 which arc not alDsolutely impenetrable, must absorb moisture from the at- 

 mosphere. Aluminous earth, reduced to an impalpable powder, has strong 

 absorbing powers. But this is not the form in which such soils can act — 

 and a close and solid clay will scarcely admit the passage of air or water, 

 and therefore cannot absorb much moisture except by its surface. Through 

 sandy soils, the air passes freely ; but most of its particles are impenetrable 

 by moisture, and therefore these soils are also extremely deficient in ab- 

 sorbent power. Calcareous earth, by rendering clay more open to the 

 entrance of air, and closing partially the too open pores of sandy soils, in- 

 creases the absorbent powers of both. To increase that power in any soil, 

 is to enable it to draw supplies of moisture from the air, in the driest 

 weather, and to resist more strongly the waste by evaporation of light 

 rains. A calcareous soil will so quickly absorb a hasty shower of rain as 

 to appear to have received less than adjoining land of different character ; 

 and yet if observed in summer, when under tillage, some days after a rain, 

 and when other adjacent land appears dry on the surface, the part made 

 calcareous will still show the moisture to be yet remaining, by its' darker 

 color. All the effects from this power of calcareous manures may be observed 

 within a few years after their application — though none of them so strongly 

 marked, as they are on lands made calcareous by nature, and in which 

 time has aided and perfected the operation. These soils present great 

 variety in their proportions of sand and clay ; yet the most clayey is friable 

 enough, and the most sandy firm and close enough, to be considered soils of 

 good texture ; and they resist the extremes of both wet and dry seasons, 

 better than any other soils wiiatever. Time, and the increase of vegetable 

 matter, will bring those qualities to the same perfection in soils made calca- 

 reous by artificial means, as they are in soils made calcareous by nature. 



The subsequent gradual accumulation of vegetable or other putrescent 

 matter in the soil, by the combining or fixing power of calcareous earth, 

 must have yet another beneficial effect on vegetation. The soil is thereby 

 made darker in color, and it consequently is made warmer, by more freely 

 absorbing the rays of the sun. 



Additional and practical proofs of all the powers of calcareous earth will 

 be furnished, when its use and effects as manure will be stated. I am 

 persuaded, however, that enough has already been said both to establish and 

 account for the diflTerent capacities of soils for improvement by putrescent 

 manures. If the power of fixing manures in soils has been correctly 

 ascribed to calcareous earth, that alone is enough to show that soils con- 

 taining that ingredient, in sufficient quantity, must become rich ; and that 

 aluminous and silicious earths mixed in any proportions, and even with ve- 

 getable or other putrescent matter added, can never form other than a 

 sterile soil. 



