terms (amounting to personal servitude) under which many of the lands are held."

"3d. The shortness of leases given by corporations (civil and religious) and by individuals, and which seldom exceed three, five, or seven years, excepting in the counties of Norfolk, Sussex, Essex, and Kent, where (with great advantage to both landlord and tenant) they are frequently extended to twenty-one years."

"4th. The tithes in kind, paid by the farmers to the church; a tax highly vexatious in its character, and oppressive in its effects: and

"5th. The poor tax, which has become enormous, and of which the yeomanry pay three fourths. Of this tax it has been truly said, that it is a powerful instrument of depopulation—a barbarous contrivance for checking all national industry."[6]

To these causes, assigned by British writers, may be added the increase of population, common to every nation of Europe, and which in Great Britain is beyond all proportion greater than the progress of agriculture; the augmentation of cattle, which occasions that of pasturage, and the diminution of tillage;[7] the establishment of great farms at the expense of small ones, and the multiplication of parks and pleasure grounds; and lastly, the attraction of great cities, and the continual drafts made upon the agricultural population, for the army and navy, and for commerce and manufactures.

SECT. III.

Theory of Vegetation.

Vegetables may be regarded as the intermediate link in the great chain of creation, between animals and minerals. The latter grow by mere chymical affinity, and by additions, sometimes analogous and sometimes foreign from their own nature; while plants, like animals, have an organization that enables them to receive their food, digest and assimilate it to their own substance, reproduce their species, and maintain an existence of longer or shorter duration. Thus far the learned are agreed, but at the next step they differ.

What is this food that gives to plants their developement, and maturity, and powers of reproduction? Lord Bacon believed that water was the source of vegetable life, and that the earth was merely its home, its habitation, serving to keep plants upright, and to guard them against the extremes of heat and cold. Tull, on the other hand, (and after him Du Hamel) pronounced pulverized earth the only pabulum of plants, and on this opinion built his system of husbandry. Van Helmont and Boyle opposed this doctrine by experiments: the former planted and reared a cutting of willow in a bed of dry earth, carefully weighed and protected against accretion by a tin plate, so perforated as to admit only rain and distilled water, with which it was occasionally moistened. At the end of five years the plant was found to have increased one hundred and sixty-four pounds, and the bed of earth to have lost, of its original weight, only two ounces. Boyle pursued a similar process with gourds, and with a similar result. Notwithstanding the apparent conclusiveness of these experiments, their authority was shaken, if not subverted, by others made by Margraff, Bergman, Hales, Kirwan, &c. &c. The first of these showed, that the rain water employed by Van Helmont, was itself charged with saline and other earthy matter; Bergman demonstrated this by analysis, while Kirwan and Hales proved that the earth in which the willow cutting was planted, could absorb these matters through the pores of the wooden box which contained it, and that a glass case could alone have prevented such absorption. Hunter, finding that oil and salt entered into the composition of plants, concluded that these formed their principal food, and accordingly recommended, as the great desideratum in agriculture, an oil compost. Lord Kaimes attempted to revive the expiring creed of Lord Bacon, but finding from Hales' statics, that one third of the weight of a green pea was made up of carbonic acid, he added air to the watery aliment of the English philosopher—but entirely rejected oil and earth, as too gross to enter the mouths of plants, and salt as too acrid to afford them nourishment. Quackery, which at one time or other, has made its way into all arts and sciences, could not easily be excluded from agriculture. Hence it was, that the Abbe de Valemont's prolific liquor, and De Hare's and De Vallier's powders, &c. &c. were believed to be all that was necessary to vegetation, and found the more advocates, as they promised much and cost little. But before the march of modern chymistry, quackery could not long maintain itself; and from the labours of Bennet, Priestly, Saussure, Ingenhouz, Sennebier, Schæder, Chaptal, Davy, &c. &c. few doubts remain on this important subject.—These will be presented in the course of the following inquiry.

1st. Of earths, and their relation to vegetation.

Of six or eight substances, which chymists have denominated earths, four are widely and abundantly diffused, and form the crust of our globe. These are silica, alumina, lime, and magnesia.—The first is the basis of quartz, sand and gravel; the second, of clay; the third, of bones, river and marine shells, alabaster, marble, limestone and chalk; and the fourth, of that medicinal article known by the name of calcined magnesia.—In a pure or isolated state,[8] these earths are wholly unproductive; but when decomposed and mixed,[9] and to this mixture is added the residuum of dead animal or vegetable matter,[10] they become fertile, take the general name of soils, and are again specially denominated, after the earth that most abounds in their compositions respectively. If this be silica, they are called sandy; if alumina, argillaceous; if lime, calcareous; and if magnesia, magnesian. Their properties are well known: a sandy soil is loose, easily moved, little retentive of moisture, and subject to extreme dryness; an argillaceous soil is hard and compact when dry, tough and paste-like when wet, greedy and tenacious of moisture; turns up, when ploughed, into massive clods, and admits the entrance of roots with great difficulty. A calcareous soil is dry, friable and porous; water enters and leaves it with facility; roots penetrate it without difficulty, and (being already greatly divided) less labour is necessary for it than for clay. Magnesian, like calcareous earth, is light, porous and friable; but, like clay when wet, takes the consistency of paste, and is very tenaceous of water. It refuses to combine with oxygen, or with the alkalies; is generally found associated with granite, gneiss, and schiste, and is