244 CALCAREOUS MANURES— APPENDIX. 



which was shelly, and of course calcareous, was entirely free from pine and 

 sorrel, and moreover was as remarkable for great and lasting fertility, as 

 the lands supposed to be acid for the reverse .qualities. Shells, or lime, 

 would necessarily combine with, and destroy, aH the previous properties of 

 any acid placed in contact ; and therefore, if acid were present universally, 

 and acting as a poison to cultivated plants, it seemed plain enough why the 

 shelly lands were free from this bad quality, and by its absence had been 

 permitted to grow rich, and to continue productive. Every new observa- 

 tion served to add strength to this notion ; and in our tide-water region 

 generally, and even in my own neighborhood, there were plenty of subjects 

 for observation and comparison, both in small shelly and fertile spots, and 

 a vast extent of poor pine and sorrel-producing lands. Siill, I could obtain 

 no direct evidence of the presence of acid, either free or combined, by ap- 

 plying chemical tests to soils, (as was tried in many cases,) nor was there 

 any authority in my oracle, Davy's 'Agricultural Chemistry,' nor in any 

 other work which I had read, for supposing vegetable acid to be present in 

 any soil. Though Davy adds to the supposition of the presence of the 

 " salt of iron," " or any acid matter," it is clear from the whole context that 

 he had in view the possible and extremely rare presence of a mineral acid 

 (as the sulphuric,) and not vegetable acid, which my views required, and my 

 proofs were afterwards brought to maintain. Sulphuric acid is sometimes 

 found in certain clays, and in combination v/ith iron is also in peat soils ; 

 but these facts have no application to ordinary soils of any country. Of 

 course, this absence of authority would, to most inquirers, have seemed 

 fatal to the position of an acid principle being generally present in the soils 

 of Virginia, and in great quantity and power of injurious action. This 

 was, indeed, a great obstacle opposed to the establishment of my newly- 

 formed opinion ; but it was not yielded to as insuperable. Diffident as I 

 then was of any such viev/s of my own, and holding the dicta of Davy as 

 the highest authority, and even his omission of any position as evidence 

 that it was untrue, or unknown, still I v/as not daunted, and supposed it 

 possible that the soils of this country might vary essentially in composition 

 in this respect, from, those of England ; or barely -possible that even the 

 great chemical philosopher might not have observed the presence of 

 vegetable acid in the comparatively few cases of its existence in English 

 soils. The later observations of subsequent years added much to my 

 evidences of the existence of acid in soils ; and still later and scientific in- 

 vestigations of chemists have served to establish that there is an acid 

 principle in most soils, in the humic or geic acid. But these discoveries of 

 chemists had not been published in 1817, (if indeed known to any) nor had 

 my own observations reached to all the proofs which I afterwards (in 1832) 

 published in the first edition (in book form) of the ' Essay on Calcareous 

 Manures,' and which were still in advance of the publication of the now 

 generally received opinions of the geic or humic acid. It must therefore, 

 be confessed, that if I reached a correct conclusion, it was not on sufficiently 

 established premises, and known chemical facts. However, reached it was, 

 whether by right or by wrong reasoning ; and however little supported by 

 direct proof or authority, I was almost sure, in advance of any known 

 experiment, first, that the cause of the unproductiveness and unfitness for 

 being enriched of most of our lands, was the presence of acid— arid secondly, 

 and consequently, that the application of lime, or calcareous earth, would, 

 by taking up and destroying the poisonous principle, leave the soil free to 

 receive and to profit by enriching manures. 



But even if this theoretical position had been demonstrated, still it might 

 furnish no jjro^toWe practical remedy. For admitting that the application 



