cacious manures as powdered lime, altho' more flow in their operation. But, as lime that has been fuffered to run into folid cakes, before it is applied to the foil, can neither be properly fpread upon it, nor has any chance of being diffolved by the action of the air afterwards,―it never can be made to produce its full influence on the foil; and therefore this mode of applying calcareous matter is the most unoeconomical that could ever be practifed. §40. Calcareous matter, alone, is not capable of rearing plants to perfection,-mold is neceffary to be mixed with it in certain. proportions before it can form a proper foil. It remains, however, to be determined, what is the due proportion of thefe these ingredients for forming a proper foil. We know that neither chalk, nor marle, nor lime, can be made to nourish plants alone; and foils are fometimes found, that naturally abound with the two first of these to a faulty degree. But, the proportion of calcareous matter in thefe, is so much larger than could ever be produced by art, where the foil was naturally deftitute of these subtances, that there feems to be no danger of erring on that fide. Probably, it would be much easier to correct the defects of those foils in which calcareous matters fuperabound, by driving earth upon them as a manure, than is generally imagined,- as a very small proportion of it fometimes affords a very perfect foil. I fhall illuftrate my meaning by a few examples. Near Sandfide, in the county of Caithnefs, there is a pretty extenfive plain on the fea-coaft, PPP fea-coaft, endowed with a moft fingular degree of fertility. In all feasons, it produces a moft luxuriant herbage, altho' it never got any manure fince the creation, and has been for time immemorial fubjected to the following course of crops. 1. Bear after once ploughing from grafs, -ufually a good crop. 2. Bear after once ploughing,-a better crop than the first. 3. Bear after once ploughing,—a crop equal to the firft. 4. 5. and 6. natural grafs, as close and rich as could be imagined,-might be cut if the poffeffor fo inclined, and would yield an extraordinary crop of hay each year. After this, the fame course of cropping is renewed. The foil that admits of this fingular mode of farming, appears to be a pure incoherent fand, deftitute of the fmalleft particle of vegetable mold,-but, upon examination, examination, it is found to confìft almoft entirely of broken shells; the fine mold here, bears fuch a small proportion to the calcareous matter, as to be fcarce perceptible,and yet it forms the moft fertile foil that ever I yet met with. I have feen many other links (downs) upon the fea-fhore, which produced the moft luxuriant herbage, and the cloffeft and fweeteft pile of grafs, where they confifted of shelly fand, which, without doubt, derive their extraordinary fertility from that cause. A very remarkable plain is found in the island of Fir-eye, one of the Hebrides.—It has long been employed as a common, fo that it has never been disturbed by the plough, and affords annually the most luxuriant crop of herbage, confifting of white clover, and other valuable pafture-graffes, that can be met with any where.-The foil confists of a very pure fhelly fand. From these examples, I think it is evident, that that a very small proportion of vegetable mold is fufficient to render calcareous matter a very rich foil. Perhaps, however, a larger proportion may be neceffary when it is mixed with clay, than with fand ;-as poor chalky foils feem to be of the nature of that compofition. At any rate, however, from thefe examples, as well as from thofe that have occurred in the preceeding parts of this essay, I think we may be fufficiently authorized to conclude, that there is no danger of ever applying calcareous fubftances to any foil in an over proportion, if that foil was not originally impregnated with fome kind of cal careous matters. $41. Calcareous matters act as powerfully upon land that is naturally poor, as upon land that is more richly impregnated with thofe fubftances that tend to produce a luxuriant vegetation, Writers on agriculture have been long in the |