No. 63.J 67 



ally be found the most simple, and at the same time the most accurate 

 of all the proposed divisions of manures. Thus humus constitutes 

 the source of the carbon, forming the principal part of the structure 

 of plants, and the salts, where they do not enter into the structure of 

 plants, are active in preparing the other inorganic elements, and ex- 

 citing the vegetable organs in their reception and appropriation of 

 nutriment. 



Humus or geine is simply decomposed animal and vegetable mat- 

 ter; and as from it, by the action of oxygen, carbonic gas is f'erived, 

 to be absorbed by water and taken up by the roots, or 



Humus or •' t j i 



Geine. mixed with the atmosphere and taken up by the leaves of 

 plants; or, as some agricultural chemists with good reason suppose, is 

 under certain circumstances dissolved, or is soluble, and thus render- 

 ed lit for immediate nourishment to plants, it must be considered the 

 most important item in the production of manures. The salts, which 

 are the most efficient in aiding vegetation, or the most active ma- 

 nures, are those formed from the alkalies and their various combina- 

 tions. Thus, from pure lime or calcium, is formed, by the union with 

 carbonic acid, carbonate of lime; with phosphoric acid, phosphate of 

 lime, the base of bones, one of the most efficient of fertilizers; with 

 sulphuric acid, sulphate of lime, or gypsum, the value of which is 

 well understood; and so with the other alkalies, which, in their com- 

 binations, form substances of the utmost consequence to plants. It 

 is well known that the outer covering of some kinds of cane, con- 

 tains so much flint or silex as to strike fire with steel; and some of 

 the grasses contain this substance in such quantity that their ashes 

 will melt into glass with potasti. Now, this hardness, so necessary 

 to their perfection, could not be attained unless this flint had been 

 rendered soluble by union with an alkali, forming a silicate of potash, 

 and by this solubility been rendered fit for the action and appropria- 

 tion of the plant. 



If we would know what kind of food is required by plants, one of 

 the first steps necessary is to ascertain of what the plants themselves 

 Food of ^'^^ composed. The combinations of matter may be said to 



Plants. ]jg absolutely endless; but the original elements of this mul- 

 titude of combinations, are few in number. Chemistry has detected 

 only some fifty-five substances incapable of further reduction, or what 

 are called simple substances; and of these, strange as it may appear, 

 only four, except in proportions merely accidental, go to the forma 



