DEDUCTIONS FROM FOREGOING DOCTRINES. 87 



less farina. Grass which grows on these spots is, both in species and taste, 

 less agreeable, and less suitable for cattle, than any other, although it yields 

 a very considerable produce in hay. In fact, in exact proportion with the 

 increase of acidity, is the decrease of the value of the soil," c. 



[If the foregoing examinations of soils, and the arguments which fol- 

 low, remain unquestioned, these two remarkable and important facts 

 may be considered as thereby established beyond dispute or doubt : 



1st. That calcareous earth, calx, or carbonate of lime, is in gene- 

 ral as entirely deficient in the soils of Virginia, as that ingredient 

 had heretofore been supposed, by agricultural writers, to be com- 

 mon in all soils ; and, 



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

 lime, 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 calca- 

 reous 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 fer- 

 tility, and perhaps show that the productive value of a soil (under 

 equal circumstances) is in proportion to the quantity of the vege- 

 table salts of lime present in the soil. The direct and positive 

 proof of this doctrine, I confidently anticipate will hereafter be ob- 

 tained from more full examinations of the humic acid, and its com- 

 pounds in various soils, and from correct and minute reports of the 

 quantities and kinds of those ingredients, in connexion with the 

 degree of the natural fertility of each soil. As yet, however in- ^ 

 teresting the recent discovery of humic acid may be to chemists, it 

 does not seem that they have suspected it to have anything like 

 the important bearing on the fertilization of soil which I had attri- 

 buted to the supposed acid principle or ingredient of soils. Ber- 

 zelius seems scarcely to have bestowed a thought on this most im- 

 portant application of his investigation of the properties of geine 

 and geic acid. 1842.] [Other authors deem not only humin but 

 also humic acid as directly fertilizing to soils, and beneficial to 

 plants ] which, as to this, or any other uncombined acid, is altogether 

 opposed to my views.* 1849.] 



* Confirmatory testimony. After treating extensively of different acids 

 of soils (humic, xilmic, crenic, apocrenic, and medusous), Johnston adds^: 

 " Besides these acids, it is known that the malic and acetic are occasionally 

 produced in the soil during the slow decay of vegetable matter of different 

 kinds. It is probable that many other analogous compounds are likewise 

 formed which are more or less soluble in water, and more or less fitted to 

 aid in the nourishment of plants." (p. 280.) The last words of the passage 



