SUPPOSITION OP ACID IN SOIL. 415 



quality, and by its absence had been permitted to grow rich, and to 

 continue productive. Every new observation served to add strength 

 to this notion ; and in our tide-water region generally, and even in 

 my own neighbourhood, there were plenty of subjects for observa- 

 tion and comparison, both in small shelly and fertile spots, and a 

 vast extent of poor pine and sorrel-producing lands. Still, I could 

 obtain no direct evidence of the presence of acid, either free or 

 combined, by applying chemical tests to soils (as was tried in many 

 cases), nor was there any authority in my oracle, Davy's " Agri- 

 cultural 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 with 

 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 views of my own, and holding the dicta of 

 Davy as the highest authority, and even his omission of any posi- 

 tion as evidence that it was untrue, or unknown, still I was 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 philo- 

 sopher 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 inves- 

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

 principle in most soils, in the humic or geic acid. But these dis- 

 coveries 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 re- 

 ceived opinions of the geic or hurnic acid. It must therefore be 

 confessed, that if I reached a correct conclusion, it was not on suf- 

 ficiently established premises, and known chemical facts. However, 

 reached it was, whether by right or by wrong reasoning ; and how- 

 ever little supported by direct proof or authority, I was almost sure, 



