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mentous subject of this Essay. In discussing the particulars re-lating to which, it may be proper,
1st, To make some inquiry regarding the soil, its ingredientsand circumstances, whether favourable or adverse to fer-tility, in order to form some judgment of the manures orsubstances which may with propriety be applied for itsmelioration, in all its different conditions ;
2d, To give a general account of the various substanceswhich have been used for the amelioration of the soil inScotland , the effects which they are supposed to produce,and the success .which has followed, according to the re-ports from the different districts j
3d, To arrange the substances employed as manures underthe classes to which they seem naturally to belong, mak-ing inquiries respecting their different properties and ef-fects ; and'in what manner any of them may be mosteconomically managed and applied ;
4th, To conclude with a few practical observations.
Sect. I.
Of the Soil in general, and of ■what composed; its Junctions, Sfc,
We often call the Soil, in common language, the Earth , notwithout propriety, it being a mixture of some of those simplebodies which philosophers have classed under the term of theEarths. Earths and stones are defined bodies, without smell,without taste, incombustible, insoluble or sparingly soluble inWater, and of specific gravity never amounting to five times theweight of water. The simple earths are always found in mix-tures or combinations with one another, frequently accompaniedwith particles of the metals, chiefly Iron ; so that we may withequal propriety call stones, petrifactions of the earths; or earth,a decomposition of stones. The simple earths discovered in thesoil are Clay, Sand, Lime, and Magnesia. Lime abounds inthe soil of some countries, particularly in some parts of Eng-land, in the form of chalk, but is very sparingly Distributed anywhere in the soil, in Scotland ; and in many places scarce anytraces of it are discoverable. Hence husbandmen have foundit advantageous to have it raised from the bowels of the earth,and carried from distant places to mix with the soil ; and onthat account it will more properly come under consideration inthe two following Sections. Magnesia is still less frequentlyfound near the surface than lime. It has been branded as hos-tile to vegetation, perhaps unjustly ; but though it should be anuseful ingredieut, nature docs not (ffer any obvious means of