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II. MANURES. 



ALL substances which, when mixed with the matter of the 

 soil tend to fertilize it, or existing in the atmosphere can be 

 drawn in by the organs of plants, and thereby contribute to the 

 progress of vegetation, are in common language termed Ma- 

 nures. Manures may be composed of animal or vegetable 

 substances or they may consist of mineral matter or, they 

 may be derived partly from mineral and partly from animal 

 and vegetable substances. They may therefore be classed, ac- 

 cording to their origin, into 1. Animal and vegetable manures. 

 2. Mineral manures. 3. Mixed manures. 



A manure may also be denned to be "the addition to land of 

 any fertilizing principle, or ingredient, in which the soil is 

 naturally deficient." The three earths, lime, alumina, (clay,) 

 and silex, (flint,) constitute, as we have already remarked, the 

 principal ingredients in all cultivated soils the richest soils 

 are those in which these three earths are mixed in the most 

 fertile proportions the excess of either renders the soil bar- 

 ren. The farmer must not suppose, however, that what is 

 commonly called clay is exclusively alumina, for such is not 

 the fact, as some stiff soils denominated clayey, have, on a 

 careful analysis, been found to contain from twenty-eight to 

 sixty-three per cent, of that material. The fact is mentioned 

 in this place in order that farmers may be on their guard. 



I. ANIMAL AND VEGETABLE MANURES. 



ON examining the constituents of vegetables, we shall find 

 that they are composed of oxygen, [formerly called vital air,] 

 carbon, [coaly matter,] hydrogen, [inflammable air,] and nitro- 

 gen, or azote, which is one of the constituent parts of the 

 atmosphere. It is evident, therefore, that the substances em- 

 ployed as manure should also be composed of these elements, 

 for, unless they are, there will be a deficiency in some of the 

 principles of the vegetable itself and it is probable that such 

 deficiency may prevent the formation of those substances 

 within it for which its peculiar organization is contrived, 

 and upon which its healthy existence depends. 



But there are likewise found in plants, though in compara- 

 tively minute quantity, certain other bodies, consisting chiefly 

 of the four earths, silica, alumina, lime, and magnesia, of the 

 oxide of iron, and, in small quantity, the oxide of manganese, 



