76 NEUTRAL SOILS. 



both precipitates (52 + 20?=) 72 J. grains of carbonates of lime 

 and magnesia, for the quantity in the original specimen of soil. 

 Yet the first operation clearly proved there could have been no more 

 than nineteen. Subsequent information and experience showed 

 that Davy's mode for separating the results of lime and magnesia 

 was as little to be relied on, as that for ascertaining the quantity 

 of carbonate of lime alone.] 



From these processes, there can be no doubt but that the soils con- 

 tained a proportion of some salt of lime (or lime combined with some 

 kind of acid), which being decomposed by and combined with the 

 muriatic acid, was then precipitated, not in its first form, but in 

 that of carbonate of lime it being supplied with carbonic acid 

 from the carbonate of potash used to produce the precipitation. 

 The proportions obtained in these cases were small ; but it does not 

 follow that the Vhole quantity of lime contained in the soil was 

 found. However, to the extent of this small proportion of lime, is 

 proved clearly the presence of enough of some acid (and that not 

 the carbonic) to combine with it. Neither could it have been the 

 sulphuric, or the phosphoric acid ; for though both the sulphate and 

 phosphate of lime are in some soils, yet neither of these salts can 

 be decomposed by muriatic acid. 



Qth. The strongest objection to the doctrine of neutral soils is, 

 that, if true, the salt formed by the combination of the lime and 

 acid must often be present in such considerable proportions, that it 

 is scarcely credible that its presence and nature should not have 

 been discovered by any of the able chemists who have analyzed 

 soils.* This difficulty I cannot remove, but it may be met (or 



* This difficulty, founded on my then profound and often misplaced re- 

 spect for all scientific authorities, would have been less, if my own acquaint- 

 ance with chemistry and chemists had been greater. Boussingault says 

 that any substance in minute quantity, not appearing among the results of 

 analyses by chemists, is by no means evidence that such substances might 

 not have been present, and even easily detected in the original body ana- 

 lyzed. Thus, he adds, "iodine and bromine for a long time escaped notice 

 in all the analyses of sea-water. Chemists, in fact, only discover readily 

 the bodies which exist in some very appreciable quantities in the com- 

 pounds they examine. The substances whose presence is not foreseen, 

 those which only enter in extremely small quantity in a mineral, are apt to 

 pass the eyes unperceived, of even the most skilful and conscientious." 

 Rur. Econ. $c., p. 205. , 



Stephens, in his late "Book of the Farm," in reference to his reports 

 of analyses of soils, says : "I regret that I must refer to foreign works to 

 furnish these analyses ; but the truth is, we have not one single published 

 analysis of British soil by a British chemist which is worth reading. Sir 

 Humphry Davy just analyzed soil to determine the amount of the first four 

 substances mentioned [silica, alumina, oxide of iron, and oxide of man- 

 ganese], and one or two others, and failed to detect five or six of the most 

 important ingredients." (P. 224, of republication in Skinner's Farmer's 

 Library.) 



