LIME PRESENT IN ALL SOILS, NOT BARREN. 89 



in excess, by exposing it to the atmosphere ; and therefore the 

 more a soil is exhausted of its fertility, the more will also be less- 

 ened its acidity, [in absolute quantity ; though not relatively to its 

 degree of fertility, which will be lessened still more.] 



We have seen from the proof furnished by the analysis of wood 

 ashes, that even poor acid soils contain a little salt of lime, and 

 therefore must have been slightly calcareous at some former time. 

 But such small proportions of calcareous earth were soon equalled, 

 and then exceeded, by the formation of vegetable acid, before 

 much productiveness was caused. The soil being thus changed, 

 the plants suitable to calcareous soils died off, and gave place to 

 others which produce, as well as feed and thrive on, acidity. Still, 

 however, even these plants furnish abundant supplies of vegetable 

 matter, sufficient to enrich the land in the highest degree ; but the 

 antiseptic power of the acid prevents the leaves from rotting for 

 years, and even then the soil has no power to profit by their pro- 

 ducts. Though continually wasted, the vegetable matter is continually 

 again forming, and always present in abundance; but must remain 

 almost useless to the soil, until the accompanying acidity shall be 

 destroyed. 



[It may well be doubted whether any soil destitute of lime in 

 every form would not necessarily be a perfect barren, incapable of 

 producing a spire of grass. No soil thus destitute is known, as the 

 plants of all soils show in their ashes the presence of some lime. 

 But it is probable that our sub-soils, which, when left naked by the 

 washing away of the soil, are so generally and totally barren, are 

 made so by their being entirely destitute of lime in any form. 

 There is a natural process regularly and at all times working to de- 

 prive the sub-soil of all lime, unless the soil is abundantly supplied. 

 What constitutes soil, and makes the strong and plain mark of 

 separation and distinction between the more or less fertile soil and 

 the absolutely sterile sub-soil beneath ? The most obvious cause 

 for this difference which might be stated, is the dropping of the 

 dead vegetable matter on the surface ; but this is not sufficient 

 alone to produce the effects, though it may be so when aided by 

 another cause of more power. When the most barren surface 

 earth was formed or deposited by any of the natural agents to 

 which such effects are attributed by geologists, it seems reasonable 

 to suppose that the surface was no richer than any lower part of 

 the whole upper stratum so deposited. If, then, a very minute 

 proportion of lime had been equally distributed through the body 

 of poor earth to any depth that the roots of trees could penetrate, 

 it would follow that the roots would, in the course of time, take up 

 all the lime, as all of it would be wanting for the support of the 

 trees } and their death and decay would afterwards leave all this 

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

 8* 



