CALCAREOUS MANURES-THEORY. 65 



increased by the deposite of every successive year, and forms those vege- 

 table soils which are called moor, peat, and bog lands. Vegetable matter 

 abounds in these soils, and sometimes it even forms the greater bulk for 

 many feet in depth ; but it is inert, insoluble, and useless, and the soil is 

 unable to bring any useful crop, though containing vegetable matter in 

 such great excess. Many millions of acres in Britain are of the different 

 grades of peat soils, of which almost none exist in the eastern half of 

 Virginia. Upon this ground of the difference of climate, and its effects on 

 fermentation, I deduce the opinion that caustic lime would be serviceable 

 much more generally in Britain than here ; and indeed that there are very 

 few cases in which the caustic quality would not do our arable lands more 

 harm than good. This is no contradiction to the great improvements 

 which have been made on many farms by applying lime ; for its caustic 

 quality was seldom allowed to act at all. Lime is continually changing to 

 the carbonate of lime; and, in practice, no exact line of separation can be 

 drawn between the transient effects of the one, and the later, but durable 

 improvement from the other. Lime powerfully attracts the carbonic acid 

 of which it was deprived by heat, and that acid is universally diffused 

 through the atmosphere (though in a very small proportion,) and is pro- 

 duced by every decomposing putrescent substance. Consequently, caustic 

 lime, when on land, is continually absorbing and combining with this acid ; 

 and, with more or less rapidity, according to the manner of its application^ 

 is returning to its former state of mild calcareous earth. If spread as a 

 top-dressing on grass lands— or on ploughed land, and superficially mixed 

 with the soil by harrowing — or used in composts with fermenting vegetable 

 matter— the lime is probably completely carbonated, before its causticity 

 can act on the soil. In no case can lime, applied properly as manure, long 

 remain caustic in the soil. Thus most applications of lime are, in effect, 

 simply applications of calcareous earth but acting with greater energy and 

 power at first, in pi'oportion to its quantity, because more finely divided, 

 and more equally distributed. 



Some account of the mode of using burnt lime in lower Virginia by 

 many farmers who cannot as well avail themselves of cheaper means to 

 render their lands calcareous, and the effects produced, will be given in a 

 subsequent part of this essay. 



By adopting the views which have been presented of the action of calca- 

 reous earth, and of lime, as manures, and those which are generally re- 

 ceived as to the modes of operation of other manures, the following table 

 has been constructed, which may be found useful, though necessarily im- 

 perfect, and in part founded only on conjecture. The various particular 

 kinds of manures are arranged in the supposed order of their power, under 

 the several heads or characters to which they belong ; and when one ma- 

 nure possesses several different modes of action, the comparative force of 

 each is represented by the letters annexed— the letter a designating its 

 strongest or most valuable agency, b the next strongest, and so on as to c 

 and d. 



