CALCAREOUS MANURES— THEORY. 55 



is now of universal acceptation. Still, notwithstanding all that has been 

 written on the subject, very little light has been thrown on it by the chemists 

 who have treated of it. Being myself too little informed to be able to pro- 

 perly digest these different speculations and to balance authorities, and to 

 separate the true and valuable from the erroneous or worthless of what 

 has been lately published, I deem it best still to rely on my own previously 

 published views and proofs only, as presented in the foregoing pages. 

 Therefore, leaving it to chemists to settle their present differences of opi- 

 nion in regard to the qualities, and even identity, as well as name of the 

 acid of soil, and to clear away the existing confusion and obscurity of their 

 views, I will, for the present, adopt nothing on their authority in this re- 

 spect. Still, I earnestly hope that their subsequent investigations may be 

 successful in eliciting and determining what is true of this acid — and also in 

 applying the truths ascertained to advance the knowledge of the composi- 

 tion and improvement of soils. For the same reason, I shall also decline 

 adopting any of the various terms which have been successively applied by 

 different, and even the same chemists, to designate the acid of soil; as 

 humic, geic, crenic and apocrenic acid, &c. 



But without the aid of this recent discovery of the humic or geic acid, 

 if the foregoing examinations of soils, and the arguments which follow, re- 

 main unquestioned, these two remarkable and important facts may be con- 

 sidered as thereby established beyond dispute or doubt : 



1st, That calcareous earth, or carbonate of lime, is in general as entirely 

 deficient in the soils of Virginia, as that ingredient had heretofore been sup- 

 posed, by agricultural writers, to be common in all soils ; and, 



2d, That, notwithstanding this total absence of the carbonate of lime, 

 that lime in some other form of combination, and in greater or less quantity, 

 is an ingredient of every soil capable of producing vegetation. 



Nor do these facts come in conflict with each other ; nor either of them 

 with the position which has been contended for, that calcareous matter in 

 proper proportions is necessary to cause fertility in soils. Should some 

 other person, who may be aided by sufficient scientific light, undertake the 

 investigation, he may supply all that is wanting for the direct proof of this 

 theory of the cause of fertility, and perhaps show that the value of a soil 

 (under equal circumstances) is in proportion to the quantity of the vegetable 

 salt of lime present in the soil. The direct and positive proof of this doctrine, 

 I confidently anticipate will hereafter be obtained from more full examina- 

 tions of the humic acid, and its compounds in various soils, and from cor- 

 rect and minute reports of the quantities and kind.s of those ingredients, 

 in connexion with the degree of the natural fertility of each soil. As yet, 

 however interesting the recent discovery of humic acid may be to chemists, 

 it does not seem that they have suspected it to have any thing like the 

 important bearing on the fertilization of soil which I had attributed to the 

 supposed acid principle or ingredient of soils. Berzelius seems scarcely 

 to have bestowed a thought on this most important application of his in- 

 vestigation of the properties of geine and geic acid. 



Supposing the doctrine to be sufficiently established by my own proofs 

 offered above, it may be useful to trace the formation and increase of acidity 

 in different soils, according to the views which have been presented, and 

 to display the promise which that quality holds out for improving those 

 soils which it has heretofore rendered barren and worthless. 



Every neutral soil at some former time must have contained calcareous 

 earth in sufficient quantity to produce the uniform effect of that ingredient of 

 storing up and fixing fertility. The decomposition of the successive growths 

 of plants, left to rot on the rich soil, continually formed vegetable acid, which, 



