Clay is a constituent of all fertile soils, though in these it rarely exceeds one-sixteenth part, and generally bears a much smaller relative proportion to the other constituents. In its pure state it is known as alumina. It is the best of all additions to light, unretentive soils, for it retains moisture much more powerfully than any other earth. M. Schubler found, that when silicious sand lost eighty-eight parts of moisture, and chalky sand seventy-six, stiff clay in the same, time lost only thirty-five parts. When clay has to be conveyed in large quantities, and to a distance, it should be dug and laid exposed in rough spits to the air for several days before it is carted, and, indeed, so should all earths; for, as Mr. Cuthbert Johnson states in his valuable Farmer's Encyclopaedia, if one hundred cubic yards of chalk, clay, or marl have to be moved, by drying previously they will lose in weight as follows: -

Chalk . . 20 to 24 tons.

Clay . . 32 " 42 "

Marl . . 18 " 26 "

For the improvement of clay lands, by rendering their staple less retentive, burning some of their own soil is an efficient application. One hundred tons per acre for this purpose are not too many; for a dressing as a manure, thirty tons are a good quantity. The following is the mode of burning clay.

"Let sods be cut of a convenient size to handle, say a foot wide and eighteen inches in length; with these form a parallelogram or long square; let the walls be a couple of feet thick, and trampled or beaten firmly together, and raised at least three feet high; the first heap should be so situated, that the wind may blow against one of its sides; it may be from four to six yards long, by three yards wide, and an aperture within one yard of each end, and others at a distance of about five feet from these should be left in the side walls, when building, for the purpose of forming drain-like openings across the heap; make one of these drain-like openings from end to end in length; these funnels are to he built also with sods; some dry turf, such as is used for fuel, is to be put into these funnels and over it, and between the funnels well-dried sods or any other combustible materials are to be laid on to the depth of a couple of feet over these sods, partially dried to the level of the walls; these materials being set on fire, a powerful heat will be produced, quite capable of burning clay, without previously drying it. Care, however, will be necessary to avoid throwing it on in too great a quantity at once, until the fire is well up, when a large quantity may be thrown on.

The sod walls are to be raised as the heap rises; and as soon as it is perceived by the strength of the smoke and glow of heat, that the mass is ignited in all its parts, the apertures may be closed up, and the heap left to become charred; should appearances indicate a likelihood of the fire being smothered, it will only become necessary to open one or more of the funnels to secure its! acting. If the land on which the burned or charred clay is to be applied be deficient in calcareous matter, earth containing it, if burned, would improve it much. If well done, there is no im-provement so cheap, and at the same time so valuable; if, on the other hand, the burning is hurried, or the fires neglected, the consequence will be, either the clay will be burned into lumps like brick ends that will not fall to pieces when exposed to the air, or the clay will not be charred or burned at all; therefore, the heat should always be slow and steady, never, if possible, burning the clay red, but black. This is difficult to manage, depending.much upon the wind, stopping up the aperture upon the windward side, and opening that on the other side.

The whole time the heaps are burning will take from two to three months, the time depending much on the weather; from sixty to one hundred yards may be burned in a heap; and if there be not sufficient sod, coarse turf, bushes, etc, on the spot to keep up a sufficient body of lire at the commencement, wood of any kind, or small coal, must be used.*' - Gard. Chron.

Clay soils are the worst that can be for gardens, for there is scarcely one of the crops there cultivated that is not injured by stagnant water, which can scarcely be prevented in clay soils at some seasons; and in wet weather clayey soils cannot be worked, whereas the gardener must be inserting or attending to his crops every day.