48 CALCAREOUS MANURES— THEORY. 



ingredients, may change the acetic to the oxalic acid, and that to any other. 

 We cannot doubt but that such simple changes may be produced by the 

 chemical powers of vegetation, when others are effected far more difficult 

 for us to comprehend. The most tender and feeble organs, and the mildest 

 juices, aided by the power of animal or vegetable life, are' able to produce 

 decompositions and combinations which the chemist cannot explain, and 

 which he would in vain attempt to imitate. 



ith. This ingredient of soils, which nourishes acid plants, also poisons cul- 

 tivated crops. Plants have not the power of rejecting noxious fluids, but 

 take up by their roots every thing presented in a soluble form.* Thus the 

 acid also enters the sap-vessels of cultivated plants, stints their growth, and 

 makes it impossible for them to attain that size and perfection which their 

 proper food would ensure, if it were presented to them without its poi- 

 sonous accompaniment. When the poorest virgin wood-land is cut down, 

 it is covered and filled to excess with leaves and other rotted and rotting 

 vegetable matters. Can a heavier vegetable manuring be desired"? And 

 as this completely rots during cultivation, must it not offer to the growing 

 plants as abundant a supply of food as they can require! Yet the best 

 product obtained may be from ten to fifteen bushels of corn, or five or six 

 of wheat, soon to come down to half those quantities. If the noxious 

 quality which causes such injury is an acid, it is as certain as any chemical 

 truth whatever, that it will be neutralized, and its powers destroyed, by 

 applying enough of calcareous earth to the soil ; and precisely such effects 

 are found whenever that remedy is tried. On land thus relieved of this 

 unceasing annoyance, the young plants of corn no longer appear of a 

 pale and sickly green, approaching to yellow, but take immediately a deep 

 healthy color, by which it may readily be distinguished from any on soil 

 left in its former state, before there is any perceptible difference in the size 

 of the plants. The crop will produce fifty to one lumdred per cent, more, 

 the first year, before its supply of food can possibly have been increased ; 

 and the soil is soon found not only cleared of sorrel, but absolutely incapa- 

 ble of producing it. I have anticipated these effects of calcareous manures, 

 before furnishing the evidence; but they will hereafter be established by 

 facts beyond conti adiction. 



The truth of the existence of either acid or neutral soils depends on the 

 existence of the other; and to prove either, will necessarily establish both. 

 If acid exists in soils, then whenever it meets with calcareous earth, the two 

 substances must combine with and neutralize each other, so far as their 

 proportions are properly adjusted. On the other hand, if I can show that 

 compounds of lime and vegetable acid are present in most soils, it follows 

 inevitably that nature has provided means by which soils can generally 

 obtain this acid ; and if the amount formed can balance the lime, the opera- 

 tion of the same causes can exceed that quantity, and leave an excess of 

 free acid. From these premises will be deduced the following proofs. 



5th. It has been stated (page 36) that the process recommended by chemists 

 for finding the calcareous earth in soils was unfit for that purpose, because 

 some precipitate was always obtained, even when no calcareous earth or 

 carbonate of lime was present. Frequent trials have shown me that this 

 precipitate is considerably more abundant from good soils than bad. The 

 substance thus obtained from rich soils by solution and precipitation, in 

 every case that I have tried, contains some carbonate of lime, although 

 the soil from which it was derived had none. The alkaline liquor from 

 which the precipitate has been separated, we are told by Davy, will, after 



* Agr. Chem. Lecture 6, page 186. 



