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each, singly and exclusively taken, may be par-ticularly examined; the experimenter may workin his laboratory with the object always in hisview; but the secret processes of vegetationtake place in the dark, exposed to the variousand indeterminable influences of the atmo-sphere, and require, at least, half a year fortheir completion. Hence the difficulty of de-termining on what peculiar circumstance suc-cess or failure depends; the diversified experi-ence of many years can alone afford a rationalfoundation for solid specific conclusions. Itcannot, therefore, be expected, that ne\v, deci-sive, and direct experiments should be laid be-fore the Academy within the time prescribed foranswering this question. The resolution of thefirst part must be deduced from a statement offacts long established by multiplied experience;and that of the second, by the application ofmore general principles to the explanation ofthose facts.—But before W'e proceed to eitherbranch of this question, the distinctions anddenominations, both of soils and manures, mustbe exactly settled and accurately defined.