Brick, a mass of clay formed into oblong squares, and dried in the open air, or burnt in proper kilns, to serve the various purposes of building.

English statute-Irichs ought, when burnt, to be nine inches long, four and a quarter broad, and two and a half thick : they are commonly used for paving cellars, sewers, sinks, hearths, etc. There is, however, a great variety of bricks, in consequence of their different forms, dimensions, uses, and the method of making them.

On comparing the strength and durability of modern bricks with those of the ancient-, it is evident that the former are in every respect inferior; and that we are either unacquainted with the exact materials of which those admirable pro-ductions of art are composed, as well as with the proper manner of preparing them; or that this useful manufacture has been shamefully neglected, while our masons and brick-makers are little, concerned about the quality of their materials, if they can obtain them in a cheap and expeditious manner. Such appears to be the tendency of the patents that have, from time to time, been procured by various scheming wen, who are generally ignorant of the first principles of chemistry on which the successful practice of this important branch of the arts chiefly depends. In order to afford a concise view of the subject, we shall premise an analysis of the r. quisites of a proper clay for making bricks; then state a few rules applicable to practice in all situations; and conclude with a general account of the late inventions, for which the King's patent has been granted: by which means the reader will be enabled to ascertain their respective merit.

It is an erroneous notion, that bricks may be made of any earth that is not stony, or even of sea-ouse ; for those only will burn red, which contain iron particles. In England, they are chiefly made of a motley, yellowish, or somewhat reddish, fat earth, vulgarly called loam. Those of Stourbridge clay, and Windsor-loam, are esteemed the most proper and durable bricks; such as will stand the greatest degree of heat, without melting. In general, the earth for this manufacture ought to be sufficiently fine, free from pebbles, and not too sandy; which would render the bricks heavy and brittle; nor too fat, which would make them crack in drying. Nor should it contain too many calcareous and ferruginous ingredients ; as the former prevent mass from becoming firm in burning, and occasion the bricks to crumble, when exposed to the air; while tire latter, or iron particles, retard the preparation of bricks, insomuch that it is sometimes impossible to give them due consistence ; this inconvenience, however, may be remedied, by allowing the clay to lie for a considerable time under the influence of the atmosphere, then soaking it in pits, and afterwards working it well, in the usual maimer. — The common potter's clay, which is also employed for the manufacture of bricks, is opaque, imparts a slight colour, sometimes yellowish, blueish, greenish, but more frequently of different shades of light-grey, excepting that of blue, which is always dark: by kneading and spreading such clay, it becomes smooth and glossy; it is soft, fat, and cold, though agreeable to the touch, slightly adheres to the tongue, and, when of the best quality, it should neither be too light nor too heavy. Its constituents chemically examined, are found to consist of thirty-seven parts of pure argillaceous or clayey earth, and sixty-three parts of sili-cious or flinty earth.

Whoever is desirous of producing the best and most durable kind of bricks, ought to attend to the following rules : 1. Clay of every description, whether fat or lean, whether more or less mixed with particles of lime, iron, etc. must be dug alter Midsummer, that is, between the beginning of July and latter end of October, before the first frost appears : it should be repeatedly worked with the spade, during the winter, and not formed into bricks till the following spring.

2. The clay, before it is put into pits for soaking, must be broken as small as possible, and allowed to lie at least ten days : every stratum of twelve inches should be covered with water, as in this manner it will be more uniformly softened.

3. Two such pits, at least, will be necessary for every brick-manufactory, so that after having been suffered to remain for five clays, the second may be prepared, and thus the manufacture carried on without interruption. 4. The next step is that of treading and tempering the clay, which requires double the labour to what is usually bestowed on it; as the quality of the bricks chiefly depends upon the first preparation. If, in tempering them, too much water be used, they become dry and brittle; but, if duly tempered, they will be smooth, solid, and durable. Such a brick requires nearly as much earth as one and a half made in the common way, when too great a proportion of water is added; in which case the bricks become spongy, light, and full of flaws, partly through neglect in working them properly, and partly by a mixture of ashes and light sandy earth (as is generally practised in the vicinity of London), with a view to dispatch and facilitate the work, as well as to save culm or coals in the burning. 5. Bricks made of proper earth, being more solid and ponderous, require a much longer time for drying than those made in the common way; they ought not to be removed to the kiln, till they have become lighter by one half, and give a hollow sound on collision; because the proper drying of bricks will prevent them from cracking and crumbling in the kiln. 6. Of whatever materials the kiln be constructed, each burning of from 6 to 10, 000 bricks requires that the fire be kept up for 24 hours, and double that time for a number of from 12 to 50, 000. The uniform increase of heat deserves great attention; the duration of it should be regulated according to the sea-sons and during the last 24 hours, the fire should be uninterruptedly-supported by means of flues ;, but afterwards the kiln must not bo suddenly closed; as there is always some danger of bursting the flue-, or melting the bricks.

It would he useless here to enter into particulars relative to the manner of burning bricks in the neighbourhood of London; we shall therefore only observe, that they are chiefly burnt in clamps built of the bricks themselves, after the manner of arches, in kilns, with a vacancy between each brick to admit the passage of the fire, but with this difference, that in-stead of being arched, the bricks project: one over another on both sides of the space, for laying in the wood and coals till they meet, and are bounded by the bricks at the top. The place for the fuel is carried up straight on both sides, till about three feet high, when it is almost filled with wood, over which is laid a stratum of sea-coal, and then the arch is spanned over. Farther, sea-coal is also strewed over the clamp, between all the rows of bricks; and lastly, the wood is kindled which also communicates with the coals; and when the whole is consumed, the manufacturer concludes that the bricks are sufficiently burnt.

Among the multiplicity of patents lately obtained for the making of bricks, it is somewhat singular, that the inventors confine their lucrative views chiefly to the formation of this useful article, without paying much regard to the materials of which it may be composed. Of this nature are the patents granted to the following individuals :

1. Mr. EDMUND Cartwkicht, of Doncaster, for his invention of a new principle, on which bricks, stones, or any other build-ing materials to be substituted for those articles, may be so form-ed, as to be applied with peculiar advantage in the erection of walls, and in the construction of (Dated April 14. 1795.) His im-provement consists in giving bricks * such a shape or form as that, when in work, they shall mutually lock into, or cramp each other. The principle of his invention, he says, will be readily understood, by supposing the two opposite sides of a common brick to have a groove or rabbet down the middle, a little more than half the width of the side of the brick in which it is made; there will then be left a shoulder on each side of the groove, each of which shoulders will be nearly equal to one quarter of the width of the side of the brick, or to one half of the groove or rabbet. —Buildings constructed with bricks of this principle, will require no bond-timber, one universal bond running through, and connecting the whole building together; the walls of which can neither crack nor bulge out, without breaking through the bricks themselves. When bricks of this simple form are used for the construction of arches, the sides of the grooves or rabbets, and the shoulders, should be the radii of the circle, of which the intended arch is to be the segment. In forming an arch, the bricks must be coursed across the centre on which the arch is turned, and a grooved side of the bricks must face the workman. They may be either laid in mortar, or dry, and the interstices after-wards filled, and wedged up, by pouring in lime-putty, plaster of Paris, grouting, or any other convenient material, at the discretion of the workman, or builder It is obvious, that arches upon this principle, having no lateral pres-sure, can neither expand art the foot, nor spring at the crown, < sequently- they will want no abutments, requiring only perpendicular walls to be let into, or to rest upon ; and they will want no incumbent weight upon the crown, to prevent their springing up; a circumstance of great importance' in many situations, in the construction of bridges. Another advan -tage attending this mode of arching is, that the centres may be struck immediately; so that the same centre (which in no case need be many feet wide, whatever may be the breadth of the arch) may be regularly shifted, as the work pro's. But the greatest and most striking advantage attending this invention is, the absolute security it affords (and at a very reasonable rate) against the possibility of lire; for, from the peculiar properties of this arch, requiring no abutments, it may be laid upon, or let i: common walls, no stronger than what are required for timbers, of which it will preclude the neces-. and save the expence. - For a more particular account, we refer the reader to the third volume of the "Repertory of Arts and Ma-nufactures" and following, o which he will also find annexed plates iliustrating the subject.

2. Mr. Francis farqharson of Birmingham, obtained a patent .20, 1798) for machi-nery for making bricks and tiles; and,

3. Mr. Janes Douglas, also, for a machine for making bricks, of the same date; but as we are not" in possession of the specifications of the two last-mentioned patents, we shall content ourselves with mentioning another, of a later date, which appears to us exceedingly ingenious.

4. Mr. Isaac Sandford, of Hartford, in Connecticut, North America, on the 20th of January, 1800, received the King's patent for a method communicated to him by Dr. A. Kinsley, of the same place, for manufacturing bricks, tiles, and pottery-ware in general, and for discharging the moulds used therein. The principle of this invention is amply detailed in the specification, a copy of which is inserted in the 13th volume of the "Repertory of Arts, " etc. p. 148, and following, illustrated by a plate. From the subjoined extract, however, the reader may form a tolerable idea of the nature and utility of this invention, which chiefly consists in a newly-contrived apparatus, for expediting the tedious process of making bricks, and other earthen-ware. - The moulds used in this machine may be various, either with false or fixed bottoms, sides, or ends ; or open at top, bottom, sides, or ends: but such as are used by the original inventor, Dr. Apollos Kinsley, are the most convenient, and contain from one to six bricks in each mould, according to their size. Each frame, or mould, has a fixed bottom ; and, when more than one brick is moulded in the same frame, or mould, the division between them is made in three parts. The middle piece is made a little tapering, and serves as a wedge to confine the other two parts in their places, while the mould is filling; and, when discharged, the wedge or middle part is lit ted out, which liberates the other two: by that means the moulds are discharged with ease. Moulds for large single bricks and ornaments, have one side, bottom, end, taken off by means of steady pins, joints, or cramps, which will confine them while filling, and may be opened in any way that will allow them to discharge. The moulds may be made of metal, or of wood and lined with metal. The-loot of the spindle may stand in, and be supported by a bar, made fast to the platform, at the bottom of the tub ; or it may be supported by a collar, inclosing the spindle-above the semi-circular sections, and made fast to the tub ; by that means the whole space under the forcers will be open, and free to form bricks and ornaments of any size or shape. The friction-rollers are placed in a frame, which may be raised or lowered by screws, according to the thickness of the bricks or ornaments ; and, by means of the screws, the moulds may be liberated from any foul matter, that may obstruct their passage through the machine. Clay for bricks, ornaments, potters-ware, and tiles, of all descriptions, may be tempered and moulded of any size, or shape, in the above-described apparatus. The clay being put into the tub, is, by the action of the sections, perfectly tempered and moulded at the same time, etc.

To conclude, we shall only add, that the reasons why the modern bricks are so very inferior to those made by the ancients; which, in their monuments, after having withstood the ravages of time tor many centuries, are still in perfect preservation, appear to be principally the following : In the present expensive state of society, the price of manual labour, though far from being adequate to the pressure of the times, is so considerable, that the manufacturer: is under a kind of necessity to make choice of those materials which are the est and most easily procured : thus, a mixture of the most improper earths and clay is often employed in the manufacture of bricks, without reflecting that two bodies specifically different in their nature, must necessarily require different degrees of heat in the kiln, in order to produce an uniform hardness, and an intimate combination of parts. On the contrary, the ancients not only selected the very best sort of clay, but combined it with other ingredients •well adapted to form the most complete cement, such as coarsely powdered charcoal and old mortar added to the clay. Of this description, likewise were the bricks which Professor Pallas, on his last journey through the southern provinces of Russia, discovered in the stupendous Tartar monuments, and which would scarcely yield to the force of a hammer. Another advantage peculiar to the bricks and tiles manufactured by our fore-fathers, arose from their method of burning them uniformly, after being thoroughly dried. There is no doubt, that if all the defects before pointed out, were removed, and modern brick-makers were to pay more attention to their art, by digging the clay at proper seasons, working it better than is done at present, bestowing more care on the burning of them, and particularly by making them much thinner than what is prescribed by the Standard form, we might produce bricks of an equal strength and durability to those of our less enlightened, but more provident and industrious, ancestors.

Brick.-layers, artisans whose business it is to build with bricks, and to perform brick-work ; such as tiling, walling, chimney-work and paving with bricks and tiles : in country places, they also undertake the masons' and plasterers' business. The London brick-layers were incorporated as a regular company in 1568, consisting of a master, two wardens, 20 assist-ants, and 78 of the livery.

The art of brick-laying has been analysed in a particular treatise by Moxov; in which he describes the materials, tools, and method of working used by bricklayers. Great care should be taken that bricks be laid joint on joint in the-middle of the walls as seldom as-may be. If they be laid in winter, let them be kept as dry as possible ; if in summer, they ought to be wetted, because they will then unite with the mortar better than if they were quite dry, and render the work much stronger.. In large buildings, or where it is too troublesome to dip eacli brick separately, water may be thrown, on every course after they are laid, as was judiciously done, when. building the College of Physicians in London, on the suggestion of Dr. Hooke. If bricks are laid in summer, they should be covered, to prevent the mortar from drying too quickly : because, thus it will not be cemented so firmly as if it were left to dry more gradually. In winter also they ought to be well covered, to protect them from rain, snow, and frost, which last is the worst enemy to mortar, especially if the work has become wet just before the frost happens.

Oil of Bricks, a singular preparation, formerly much esteemed in the cure of many diseases; but now justly exploded as absurd and pernicious Father than useful. It is obtained by soaking fragments of bricks in olive oil, and afterwards distilling them in the usual manner. In the present improved state of chemistry, it has been found that, by this fanciful process, the oil of olives, so far from being impregnated with healing ingredients, is necessarily corrupted.

Brick-ivatcr, or water impregnated with the contents of bricks, is possessed of properties so peculiarly striking, and at the same time so pernicious in their effects, when used for culinary purposes, that we cannot, in justice to our readers, withhold from them the following curious experiment made by Dr. Percival, and stated in the first volume of his Essays. He steeped two or three pieces of common brick, four days in a bason full of distilled water, which he afterwards decanted off, and examined by various chemical tests. It was hot miscible with soap; struck a lively green with syrup of violets ; became slightly lactescent by the volatile alkali; but entirely milky by the fixed alkali, and by a solution of sugar of lead. No change - produced on it by an infusion of tormentil-root. Hence the Doctor justly concluded, that the lining of wells with bricks, a practice very common in many places, is extremely improper, as it cannot fail to render the water hard and unwholesome. Clay generally contains variety of heterogeneous matters; and coloured loams often participate of bitumen, and the ochre of iron. Sand and lime-earth are still more common ingredients in their composition ; and the experiments of Mr. Geoffrey and Mr. Pott prove, that the earth of alum also may in considerable quantity be separated from clay. As therefore clay is exposed to the open air for a long space of time, before it is moulded into bricks and burnt, this process in many respects resembles that by which the alum stone is prepared. And it is probable, that the white efflorescence, which is frequently observable on the surface of new bricks, is of an aluminous nature: indeed the combination of the vitriolic acid with the earth of alum, may be sufficiently accounted for, partly from the long exposure of clay to the air, before it is moulded into bricks, and partly from the sulphureous exhalations of the pit-coal used for burning them, together with the suffocating, bituminous vapour arising from the ignited coal.