or lefs proper for different foils. In those calcareous fubftances that belong to the animal kingdom, the fleshy parts of the animals may be, fometimes, united with the calcareous, which will greatly promote their effects as a manure, on every kind of foil whatever. This does not, however, feem to be the cafe, either with fhell marle, or fine fhelly fand; as, in both these cafes, the animals, which once inhabited these shells, have been fo long dead, that no part of the fleshy fubftance can remain. But the recent fhells, obtained from fifhing towns, operate much more powerfully as an animal manure, than as a calcareous matter, when first applied. It is not impoffible, but that man may, in time, fall upon fome contrivance, for obtainning this animal calcareous manure, in much greater abundance and perfection, than it has hitherto been ever obtained. There is a a fmall fpecies of fresh water wilk, which encreafes fo fait, as in a furprising short time to fill a confiderable space with folid wilks, if a few of them have been placed in a proper receptacle for that purpose, and water duly adminiftred to them.—If then, ponds were prepared for this purpose, and properly flocked with this animal, and if they were allowed to increafe, till a bed of them of confiderable thickness was accumulated, might they not, then, be taken out in abundance to be employed as a manure? Thefe, if bruifed under a ftone like a tanner's wheel, to reduce the fhells to small fragments, would certainly form as rich and efficacious a manure as could poffibly be devifed :-Nor could there be any difficulty in difpofing the ponds in fuch a manner, as to afford a conftant annual supply. · It has probably been by a natural process, fimilar to this, that all thofe beds of fhell marle we now meet with, have been origi nally nally produced. This fpecies of marle is generally found to confift of the fhells of this fort of fmall wilk, more or less decompofed. The animals which inhabited these shells, have been once nourished by the water contained in thofe hollow places where this fort of marle is always found, and have probably been entirely destroyed by fome accidental drought, which deprived them of the water neceffary for their exiftence, or to fome other difaftrous circumftance that it is impoffible for us now to point out; and the fhells remaining behind, have gradually mouldred down to the ftate in which we now find them. § 39. The fame quantity of calcareous matter, will, in all cafes, operate equally power fully fully on foils of a fimilar quality, and in a fimilar state. But these effects may be more accelerated or retarded,-be more uniform or unequal, according as the calcareous matter is more or lefs perfectly divided when it is first applied to the foil. If the calcareous matter be divided into very small particles, fo as to admit of being equally fpread over a very large furface, a fmall quantity of it will produce a much more fenfible effect, than if the fame quantity of calcareous matter had been applied in large lumps, which could, in that cafe, have operated only upon a very few particles of the foil;-Therefore, lime, fine fhelly fand, or fhell marle, if equally pure, may be applied with profit, in much fmaller quantities than other clafs of calcareous manures. any Hence alfo it follows, that, if equal quantities of calcareous matter are employed as a manure, that which admits of being most minutely minutely divided, will produce the greatest effect at the beginning; because, the separate particles will be at liberty to act on a much greater number of particles of the foil at once, than when it is lefs perfectly divided. But, if a sufficient quantity of calcareous matter has been applied, when in pretty large maffes, fo as to cover the ground pretty equally; and if thefe lumps continue to diffolve in the foil in all after periods, the effect of this dreffing will be much longer perceived, than that of a dreffing of calcareous matter in fine powder, that should produce at first an effect equal to this.-Perhaps, in this cafe, the virtue of every particle of the calcareous matter will come in time to produce a full effect upon the foil, and benefit it as much as an equal quantity of very fine powdered calcareous matter would have done, applied at different times. Stone and clay marles, therefore, are equally effi cacious |