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advocates for salts, when they are obliged to admit that vegeta-.bles derive no direct food from salts, contend, that these substan-ces either whet the appetite, or fit the food for the vegetable pa-late. It would be improper to swell this work by entering intodiscussions upon such dark and doubtful topics- The husband-man’s duty is to give his soil the proper consistence, and store itwith known vegetable aliment. When that is done, the condi-ment, if condiment be necessary, will not be wanting.
3d. Mixed .—The last order of fossil manures is, substanpes inwhich calcareous is mixed with other earths. These are, stoneor rock marl, clay mail, shell sand. To these may be addedschistose substances, containing some calcareous matter, butscarce enough to deserve the name of marl.
Stone and clay marl probably difFer only from each other onaccount of the situation in which they have been respectivelylodged. The former, laid on a dry bed, and compressed undera dry covering, is indurated like a stone ; the latter, lodged in awet hollow, and covered with spongy matter, has continued soft.These mixtures seem to be happily modified. After being some-time exposed to the weather, they crumble into friable matter,and do not form again into cohesive masses. Neither do thesekinds of marl, like shell marl, occasion a faulty porosity in thesoil, where they have been copiously applied, fields are to beseen on which they have been laid, at the rate of 400 cart loadsand upwards, perhaps 40 years ago, which, whenever they arelaid in grass, bear a close cover of the sweetest herbage. Itwould seem that the other earths are so modified as to counter-act the repulsive quality of the calcareous, and preserve that me-dium of consistence so favourable to permanent fertility.
Shell sand, being a mixture of calcareous and silicious earths,ig evidently an appropriate manure for correcting the defect oftoo cohesive soils ; and by it, such soils, when they lie near thecoasts, where this substance is found, may be greatly amelio-rated.
The schistose substances mentioned, are chiefly found in thedistricts where the coal strata lie. They are laid in thin laminsover one another, and frequently covered with a bed of free-stone. They are hard, and quite sterile in their native state:but in deep sections of the country, where the face is exposedto the vicissitudes of the weather, they gradually moulder down,and lie soft and mellow at the bottom, showing no tendency tocoherence. Where any considerable mass of this matter is form-ed, plants of different kinds are found growing in it with greatluxuriance. When they are spread on grass ground, and lie tillthey crumble with the weather, a deep verdure ensues. It would.appear therefore, that they possess the true consistence of a fer-tile soil ; and where they could be raised on easy terms, a tbickcoat of them laid on any thin poor land, in the immediate neigh -