70 CHEMICAL AUTHORITY OPPOSED TO ACID 



tains the following passage : " Chalk has been recommended as a 

 substance calculated to correct the sourness of land. It would 

 surely have been a wise practice to have previously ascertained this 

 existence of acid, and to have determined its nature, in order that 

 it might be effectually removed. The fact really is, that no soil 

 was ever yet found to contain any notable quantity of acid. The 

 acetic and the carbonic are the only two that are likely to be gene- 

 rated by any spontaneous decomposition of animal or vegetable 

 bodies, and neither of them have any fixity when exposed to the 

 air.' 7 Thus, then, my doctrine is deprived of even the feeble sup- 

 port it might have had from Dundonald's mere opinion, if that 

 opinion had not been contradicted by later and better authority ; 

 and the only support to be looked for, will be in the facts and argu- 

 ments that I shall be able to adduce. 



I am not prepared to question what Gftisenthwaite states as a 

 chemical fact, "that no soil was ever yet found to contain any 

 notable quantity of acid." No soil examined by me for this pur- 

 pose, with such poor means as I could apply, gave any evidence of 

 the presence of uncombined acid. Still, however, the term acid 

 may be applied with propriety to soils in which growing vegetables 

 continually receive acid from the decomposition of others (for which 

 no " fixity" is requisite), or in which acid is present, not free, but 

 combined with some base, by which it is readily yielded, to promote, 

 or retard, the growth of plants in contact with it. It will be suffi- 

 cient for my purpose to show that certain soils contain some sub- 

 stance, or possess some quality, which promotes almost exclusively 

 the growth of acid plants that this power is strengthened by 

 adding known vegetable acids to the soil and is totally removed 

 by the application of calcareous manures, which would necessarily 

 destroy any acid, if it were present. Leaving it to chemists to 

 determine the nature and properties of this substance, I merely 

 contend for its existence and effects; and the cause of these effects, 

 whatever it may be, for the want of a better name, I shall call 

 acidity. 



The proofs now to be offered in support of the existence of acid 

 and neutral soils, however weak each may be when considered alone, 

 yet, when taken in connexion, will together form a body of evidence 

 not easily to be resisted. 



First proof. Pines and 'common sorrel \rumex acetocella] have 

 leaves well known to be acid to the taste ; and their growth is fa- 

 voured by such soils as are here supposed to be acid, to an extent 

 which would be thought remarkable in other plants on the richest 

 soils. Except wild locust on the best of our.river land, no growth 

 can compare in rapidity with pines on soils naturally poor, and 

 even when greatly reduced by long cultivation. Pines usually 

 stand so thick, on old exhausted fields, that the increase of size in 



