.ACID AND NEUTRAL SOILS DEFINED. 69 



Tn all naturally poor soils, producing freely pine and whortle- 

 berry in their virgin state, and sheep-sorrel after cultivation, I sup- 

 pose to have been formed some vegetable acid, which, after taking 

 up, ancl combining with whatever small quantity of lime might 

 have been present, still remains in excess in the soil, and nourishes 

 in the highest degree the plants named above, but is a poison to all 

 useful crops ; and effectually prevents such acid soils from becom- 

 ing rich, by either natural or artificial applications of putrescent 

 manures. 



In a neutral soil, I suppose calcareous earth to have been suffi- 

 ciently abundant at some former time to induce a high degree of 

 fertility but that it has been decomposed, and the lime taken up, 

 by the gradual formation of vegetable acid, until the lime and the 

 acid neutralize and balance each other, leaving no considerable ex- 

 cess of either ; and thaff such are all our fertile soils which are not 

 now calcareous. 



Both these suppositions remain to be proved, in all their parts. 



No opinion has been yet advanced that is less supported by good 

 authority, or to which more general opposition may be expected, than 

 that which supposes the existence of acid soils. The term sour soil 

 is indeed frequently used by farmers, but in so loose a manner as 

 to deserve no consideration. It has been thus applied to any moist, 

 cold, and ungrateful land, without intending that the term should 

 be literally understood, and perhaps without attaching to its use 

 any precise meaning whatever. Dundonald only, of all those 

 who have applied chemistry to agriculture, has asserted the exist- 

 ence of vegetable acid in soils :* but he has offered no analysis 

 of soils in proof, nor any other evidence to establish the fact ; and 

 his opinion has received no confirmation, nor even the slightest no- 

 tice, from later and more able investigators of the chemical cha- 

 racters of soils. Kirwan and Davy profess to enumerate all the 

 common ingredients of soils; and it is not intimated by either 

 that vegetable acid is one of them. Even this tacit denial by 

 Davy more strongly opposes the existence of vegetable acid, than it 

 is supported by the opinion of Dundonald, or any early writers on 

 agriculture, if there be any who may have admitted its existence. 

 [For it cannot be supposed that so able and profound an investiga- 

 tor would have omitted all reference to an ingredient of soils so 

 general, and therefore so important, as is here asserted, even if its 

 presence had been even suspected by him, much less if fully known.] 

 Grisenthwaite, a late writer on agricultural chemistry, and who has 

 the advantage of knowing the discoveries, and comparing the 

 opinions, of all his predecessors, expressly denies the possibility of 

 any acid existing in soils. His New 'Theory of Agriculture'^ con- 



* Dundonald's Connexion of Chemistry and Agriculture, 

 j- Republished in American Farmer, (old) vol. ii. 



