soils and organizable matters which may be regarded as chemical. The earths, and even the earthy carbonates, have a certain degree of chemical attraction for many of the principles of vegetable and animal substances. The extract from decomposing vegetable matter, when boiled with pipeclay or chalk, forms a combination by which the vegetable matter is rendered more difficult of decomposition and of solution. Pure silica and siliceous sands have little action of this kind; and the soils which contain the most alumina and carbonate of lime, are those which act with the greatest chemical energy in preserving manure. Such soils merit the appellation which is commonly given to them, of rich soils; for the vegetable nourishment is long preserved in them, unless taken up by the organs of plants. Siliceous sands, on the contrary, deserve the term hungry, which is commonly applied to them; for the vegetable and animal matters they contain, not being attracted by the earthy constituent parts of the soil, are more liable to be decomposed by the action of the atmosphere, or carried off from them by water. In most of the black and brown rich vegetable moulds, the earths seem to be in combination with a peculiar extractive matter, afforded during the decomposition of vegetables: this is slowly taken up and attracted from the earths by water, and appears to constitute a prime cause of the fertility of the soil." This extractive matter is identical with the black reduced substance of old dunghills, now called humus.

8. Soils may be improved by pulverization, or the minute division of the particles by mechanical labour, and under this term are included the operations of ploughing, harrowing, digging, trenching, hoeing, and raking. It is of the most essential service to land, and induces fertility in a variety of ways. It opens the ground, and thus gives scope to the roots of vegetables; increases its sponge-like property, and thus promotes the regular diffusion of water. It tends to increase the quantity of vegetable food, by enabling the water holding nutritive matters in solution, to convey it more equally to the roots of plants. Pulverization, by opening the soil, promotes and assists the free ingress of heated air, and thus regulates and improves the temperature of the soil; it also introduces, and, as it were, buries a considerable portion of atmospheric air, and thus furnishes another source of electro-chemical decompositions and combinations.

"The depth of pulverization, Sir Humphry Davy observes, must depend upon the nature of the soil and the sub-soil. In rich clayey ground it can scarcely be too deep; and even in sand, unless the subsoil contains principles noxious to vegetables, deep comminution should be practised. When the roots are deep, they are less liable to

be injured, either by excess of rain or drought; the radicles are shot forth into every part of the soil, and the space from which the nourishment is derived, is more considerable than when the seed is superficially inserted in the soil." The force of this remark applies strictly to vegetable crops; for as to fruit-trees, a stratum of hard brick-bats, or rocky chips, under a surface soil of turfy loam, not exceeding fourteen inches, would be far more congenial to their roots than a deep bed of prepared, and especially, of manured earth.

9. A free admission of air, and exposure to the influence of heat and cold, tend to improve the ground. "If the soil be laid up in large lumps (or ridges), it is evident it will acquire more heat, by exposing a greater surface to the atmosphere; and it will retain this heat longer, from the circumstance of the lumps (or ridges) reflecting back the heat radiated by each other. A clayey soil, in this way, it is said (Farmer's Magazine, 1815), may be heated to 120 degrees. By the aëration of lands in winter, minute mechanical division is obtained by the freezing of the water in the soil; for as water in the solid state occupies more space than when fluid, the particles of earthy matters, and of decomposing stones, are thus rent asunder, and crumble down into fine mould."

10. Soils may be improved by adding to, or subtracting from them, ingredients in which they are deficient, or superabound. If a soil, of good appearance and texture, contain sulphate of iron, it may be ameliorated by quick lime; if there be excess of calcareous matter, it may be improved by the application of sand or clay. Soils too abundant in sand are benefitted by the use of clay, marl, or vegetable

matter.

By burning soils, considerable chemical changes can be brought about. "The bases of all common soils are mixtures of the primitive earths and oxide of iron; and these earths have a certain degree of attraction for each other." "When clay or tenacious soils are burnt, they are brought nearer to a state analogous to that of sand. In the manufacture of bricks, the general principle is well illustrated: if a piece of dried brick-earth be applied to the tongue, it will adhere to it very strongly, in consequence of its power to absorb water; but after it has been burnt, there will be scarcely any sensible adhesion."

"The soils improved by burning are all such as contain too much dead vegetable fibre; also all such as contain their earthy constituents in an impalpable state of division, that is, stiff clays and marls; but coarse sands, or rich soils, containing a just mixture of the earths; and in all cases in which the texture is sufficiently loose, or the organizable matter sufficiently soluble, the progress of burning cannot be useful."

ANALYSIS OF SOILS.

In this place, before we enter upon the consideration of manures and composts, it will be proper to introduce the reader to an acquaintance with the general constituents of native earths; referring him, as standards of comparison, to HENRY'S Epitome of Experimental Chemistry, and to DAVY's Agricultural Lectures on the subject of Analysis of Soils. The directions given by these chemists are very instructive, but the tyro will require them to be rendered rather more explicit. I have attempted to do so. The processes now to be described are founded upon the experience of years, simplified improved by much practice.

Chemical research cannot fail to instruct and rationally entertain. As respects the soil, it is the only sure guide which may, and ought to be, appealed to by the gardener and farmer in every case of doubt and perplexity; for earths and soils can never be understood, or scientifically meliorated, till their components be discovered and calculated by means which cannot mislead. The various processes will be distinguished by italic letters.

The apparatus described by the chemists above named, consists of a balance capable to contain four ounces of the soil, and so finely suspended, as to turn when weighted with a single grain; and a series of weights, from one grain to a pound troy. A nest of brass weights, comprising all the divisions of a pound, from two drachms to eight ounces, is extremely convenient; but, in addition to this, there ought to be duplicates of all the smaller weights, from half a grain to two drachms of the apothecary's table, and a pair of fine money-scales; for it frequently happens that one or more of the products does not exceed a grain or two, and can scarcely be weighed in the larger balance.

A wire sieve, sufficiently coarse to admit a peppercorn to pass through it, is mentioned; but as the object is to separate the stones and large fibres from a soil, it would appear better that the apertures of the sieve be so fine as to retain a grain of mustard seed.

An argand lamp and stand, some glass bottles, Hessian crucibles, porcelain and queen's-ware evaporating basins, a Wedgewood pestle and mortar, some filters made of white blotting-paper, folded so as to contain from a quarter of a pint to a pint of liquid, and greased at the edges, two small glass funnels, a bone-knife, and an apparatus for collecting and measuring aëriform fluids (gases), complete the catalogue of vessels and utensils.

I have been somewhat minute in this quotation, in order to

prevent misconception; but the student, unless it be his object to enter into any minute research, will not indispensably require the gas apparatus, or the argand lamp. A temporary furnace may be constructed with two garden-pots, which will supply the place of the latter, and, with some slight modification, it may be applied to keep frost out of a green-house or pit. For chemical experiments, a pot six inches deep, and five inches wide at the rim, is large enough. A small iron grate, or a round plate, perforated with a number of holes to admit air, must be made to drop into the pot, and fit it, two or three inches above the bottom; and under this, two or three air-holes must be made. Another pot, of a size, when inverted, to fit the lower one, by dropping half an inch within its rim, is to have its bottom beaten entirely out. This pot, turned upon the other, will serve as a stand to support a Florence flask, or an evaporating basin. To use the furnace, a little good charcoal is placed on the grate; five or six pieces more, ignited, and red hot, are put upon that, and over those a little more cold charcoal. If the small pot be inverted within the lower one, the charcoal will be speedily kindled. Should the fire be fierce, it will be prudent to employ a stand, with moveable rings, by means of which the vessel to be heated may be raised or depressed; and practice, with discretion, will soon teach the requisite caution. As the fire-pot is liable to crack, it may be secured by one or two iron hoops, or by being bound, in two places, by strong and flexible copper wire.

To reduce and economize the heat of a furnace of this kind, it will only be requisite to cover the upper pot with a slate or flat piece of iron, to a greater or less degree. The rush of air through the holes under the grating will bring the charcoal into a state of rapid combustion; but as the gas produced at top is carbonic acid, -an elastic fluid wholly inimical to fire, the combustion will, if its egress be checked, be proportionably abated, or entirely suspended. If, then, two pots of rather larger dimensions be employed, and the upper one be almost filled with charcoal, a fire, diffusing a gentle warmth, may be maintained during a whole night, by nearly closing the upper orifice, and covering the junction of the two rims with a little powdered charcoal. Half a gallon of good, well-burnt charcoal, has been found to keep a house twenty feet long, at nearly forty degrees of heat, the external air being three or four degrees below the freezing point.

The chemical tests, or re-agents, which will be required are, muriatic acid (spirits of salts), solution of prussiate of potash, sulphuric acid (oil of vitriol), soap-lye (liquid caustic or pure soda), solutions of pure ammonia, of carbonate of ammonia, and of carbo

nate of potash, or salt of tartar. All, or any of these, can be readily procured of any respectable druggist, and most of them may be prepared, and thus become a source of great pleasure to the intellectual experimenter.

PROCESSES OF ANALYSIS.

(a) Preparation of the earth to be examined.-Let one ounce troy, that is, 480 grains of it, be rendered so dry, by exposure in a saucer to air and sun in summer, or before a fire in winter and damp weather, that it may be easily reduced to powder; when in that state, let it be passed through the sieve, and the siftings weighed. Their weight being noted, they are to be put into a saucer and dried by a heat not less than that of boiling water, for half an hour. The power of absorption and of retention is thus ascertained; and on this subject Davy observed,-" The loss of weight in this process should be carefully noted; and when in 400 grains of soil it reaches fifty grains, the soil may be considered as in the greatest degree absorbent, and retentive of water, and will generally be found to contain a large proportion of aluminous earth. When the loss is only from twenty to ten grains, the land may be considered as only slightly absorbent and retentive, and the siliceous earth as most abundant."

Whatever be the loss of weight by drying in high temperature, no just estimate can thence be formed of the quality of a soil. I have repeatedly analyzed a loam essentially siliceous, wherein there were very few stones, and little coarse sand: it was highly valuable as a staple soil, of a delicate and velvety texture, and peculiarly adapted to the finer operations of the garden, and in the forcing departments; yet it retained so small a proportion of water that only five and a-half per cent. could be expelled at a high degree of heat.

(b) The coarse stones separated by the sieve, should be weighed, placed in a wine glass, and tested by dropping upon them a little muriatic acid, diluted with its own weight, or measure, of water. If much hissing arise, it will be manifest that they contain carbonate of lime. If no action is perceptible, they consist chiefly of flint, and in that case will be sufficiently hard to scratch glass. The fibrous matters, if considerable, ought to be weighed, and the weight noted down.

(c) Process of washing to obtain vegetable extract.—Take 300 grains of the dried pulverized earth, after it has become quite cold, and boil it for ten minutes in four ounces of pure rain water. The vessel should be a small evaporating basin, with a lip. Let the liquor cool, and then decant off as much of the clear fluid as possible.