From this analysis, we see it appears to be neither a variety of talc nor of meerschaum, but rather a hydrate of silica. Sir Henry Wotton speaks of a sort of bricks at Venice, of which stately columns were built; they were first formed in a circular mould, and cut, before they were burnt, into four or more quarters or sides; afterwards, in laying, they were joined so close, and the points concentrated so exactly, that the pillars appeared one entire piece. In modern times brick-making is nowhere carried to greater perfection than in Holland, where most of the floors of houses and often the streets are paved with excellent and very durable bricks.

Loam and marl are considered the best English materials for bricks. The former is a natural mixture of sand and clay, which may be converted at once into this useful manufacture; marl is a mixture of limestone and clay in various proportions. The best proportion for common bricks would be three parts of clay, and one part of limestone or chalk powdered. Such a mixture exposed to heat experiences an incipient fusion, and thereby is rendered much harder and denser; it imbibes much less water than any other material, and is therefore much less liable to crack and fall to pieces in winter.

We cannot here enter into details respecting the chemical investigations of different periods as to the nature of clay. Suffice it to say, that during the last century the labors of Pott, Baume, and Margraaf, threw a sufficient light upon the subject to enable us to pronounce it a mixture of alumina and silica, in different proportions. It was shown at the same time that it also frequently contains sulphuric acid and potash. More recent researches have likewise discovered in its composition mica, chalk, felspar, hornblende, bitumen, oxide of iron, and coal, which modify its qualities considerably, and adapt it for the various purposes of different manufactories.

The neighbourhood of London is remarkably adapted for the making of bricks, the soil of the whole surrounding country being clay at a certain depth, generally under a bed of gravel; and the bottom of the Thames yielding the sand which is used in this manufacture. Here, too, of course, is an uncommon consumption of them; and although from the peculiar advantages of the spot an excellent yellow brick has long distinguished the manufacture of the metropolis, great practical carelessness seems to pervade the whole business as conducted here. We see no reason why our Dutch neighbours should so decidedly excel us in this particular; except that the spirit of a short-sighted parsimoniousness has crept into this as into many other of our calculations; that is, houses are built in and about London, not to endure nor to sell, strictly, but to let, and that for comparatively short leases. frequently. Hence our ordinary

architects and takers of building leases have no part in the ambition of rearing an 'eternal city:' whole streets may be seen in youth decrepid,' propped, and tottering, sometimes before tenanted, and the greater number of bricks used are not above half kneaded and half burnt.

Brick-clay is generally dug out and exposed at the end of one season, for the operations of the next. It should always be laid open to the air and weather for a considerable time; and if for two or three seasons, the bricks will be the better made. The stones of which the clay has been originally formed, thus become more completely decomposed, and the clay itself better pulverised. The frosts of winter, too, temper and mellow it very beneficially. It should be often turned over, and afterwards ground by a mill to a complete powder; but ordinarily the clay is tempered by the treading of men or cattle; the earth being thrown into shallow pits, where it is wrought and incorporated, until formed into a homogeneous paste. This is facilitated by occasionally adding small quantities of water; but the less water that is used, the better for the substance of the clay, which will be more tough and gluey, and consequently the bricks will be smoother and more firm. This is the most laborious, and perhaps most essential, part of the process; to the negligence of which we are to attribute almost all the bad qualities of modern bricks; hence are they light, soapy, spongy, and full of cracks. Whereas, if the clay be properly tempered, they are hard, ponderous, and durable. M. Gallon having taken a quantity of brick-earth tempered in the usual way, let it remain exposed to the air for seven hours, and then caused it to be moistened and beaten for the space of half an hour; the next morning the operation was repeated; and in the afternoon the clay was again beaten for fifteen minutes more; making the whole additional labor an hour and a quarter. The bricks made of this earth being dried in the air for thirteen days, and burned along with the rest without any particular precautions, were found to be not only heavier than common bricks, but also very different in strength; for on placing their centre on a sharp edge, and loading both the ends, Mr. Gallon found, that while it took a weight of 65 lb. at each end to break them; other bricks were broken by the weight of only 35 lbs. The improvement in the quality of the article thus far exceeding the additional labor.

A proper quantity of coarse sand is a fine annealer of brick-clay; it answers best when the particles are of such a size as to be readily distinguished by the eye. When as large as coriander seeds, it has been found to answer better than when very fine.

London brick-makers add also about one-third part of ashes or small coal to their clay, the consequence of which is said to be that when the mixture is sufficiently heated afterwards, those fires burn of themselves, and are chiefly fed with the fuel supplied by the clay. Bricks, according to Mr. Malcolm, are made by the thousand, as the most satisfactory mode between master and man, and a handy man could mould in one day, viz. from five in the morning until eight at night,

5000.

he

To assist him in the preparation of the soil, &c. from the heap (which is usually dug after the season for brick-making is over, and laid up), there is generally a gang, consisting of six persons; one man tempers and prepares the soil, which is done with a hoe made long, in the shape of a mattock, a shovel, scoop,, a thick plank or board, and a cuckhold; with the hoe pulls down the soil from the great heap, which is chopped backwards with the shovel, to turn it as often as may be necessary, to mix and thoroughly incorporate the ashes and soil together, because it is to be understood, that at the time the soil is dug out, and made into this heap, a layer of coal ashes is alternately placed between a layer of soil, as often and in such quantities in each layer as the quality of the soil and other circumstances may make necessary. The scoop is used to throw water over this portion that is pulled down with the hoe, in order that it may become, more and more, in a tempering state, more soft and ductile; and with the board he kneads it together, over which a certain quantity of sand is thrown, and it is then covered with pieces of sacking or matting, to keep the sun and air from it. A boy scoops or cuts off a slice, with an instrument or shovel having a short handle, and the blade of it made concave, called a cuckhold; this he brings on his arms to the inoulding table, which is placed under a moveable shed, upon which, another boy rolls out a lump somewhat bigger than will fit the mould, the table have been previously strewed with sand. The moulder, after dipping his mould into dry sand, placed at one corner of his table, throws the lump prepared into the mould, and with a flat smooth stick, about eight inches long, previously dipped in a pan of water, strikes off the surplus soil; he then immediately turns out the brick upon a stand, or board, of the same size with the brick; a boy takes it from thence, and places it on a light barrow, with a latticework frame fixed over the frame of the barrow, at about three feet high above the wheel, and reduced to about eighteen inches in height towards the handle, forming an inclined plane. The new made bricks are placed on this lattice frame, and over them sand is thrown in sufficient quantities to prevent their adhering to each other, as well as to prevent, in a certain degree, their cracking in drying while on the hacks. A boy wheels the barrow to the hacks, and places them with great regularity and despatch, one above the other, a little diagonally, in order to give a free passage to the air. Each hack is made wide enough for two bricks, to be placed edgeways across, with a passage between the heads of each brick; they are usually made eight bricks high; the bottom bricks at the end of each hack are old ones.

Wheat or rye straw is, in showery weather, carefully laid over the hacks, at least near London, where the brick-makers do not, as in some places distant from the metropolis, go to the expense of roofed coverings, or sheds; their works being too extensive. If the weather is tolerably fine, a few days is sufficient to make them dry enough to be turned, which is done by resetting them more open, and turning them; and six or

eight days more are required before they are fit to be put into the clamp or kiln for burning. Bricks throughout the country are generally burnt in a kiln thirteen feet long, by about ten feet and a half wide, and twelve feet in height. It will hold about 20,000 bricks. The walls are one foot two inches thick, carried up a little out of the perpendicular, inclining towards each other at the top. The bricks are placed on flat arches, having holes left in them resembling lattice work; the kiln is then covered with pieces of tiles or bricks, and some wood put in, to dry them with a gentle fire. This continues two or three days before they are ready for burning, which is known by the smoke turning from a darkish color to transparent. The mouth or mouths of the kiln are now dammed up with a shinlog, or pieces of brick piled one upon another, and closed with wet brick earth, leaving above it just room sufficient to receive a faggot. The faggots are made of furze, heath, brake, fern, &c. and the kiln is supplied with these until its arches look white, and the fire appears at the top; upon which it is slackened for about an hour, and the kiln allowed gradually to cool. This heating and cooling is repeated until the bricks are thoroughly burnt, which is generally in forty-eight hours. Near London, when the bricks are sufficiently dried by the air, the clampmaker levels the ground, at one end of the range of hacks, making the foundation of the intended clamp somewhat higher than the surrounding ground; and with place bricks, if they have any, or otherwise with the driest of those just made, makes a foundation of an oblong form, beginning with the flue, which is nearly a brick wide, and running straight through the clamp. In this flue, dry bavins, coals, and cinders, vulgarly called breese, are laid and pressed in close, in order that the interstices between wood and coal may be properly filled up. On the sides of the flue, the bricks are placed diagonally about one inch asunder, and between each layer of bricks three or four inches of breese are strewed, and in this manner they build tier upon tier as high as the clamp is meant to be; never omitting between each layer, as well as between each brick that is placed diagonally, to put a due portion of breese. When they have made the clamp about six feet long, another flue is made similar in every respect to the preceding, to the extent of the size of the intended clamp, provided only that the bricks are meant to be burnt off quick, which they will be in about twenty-one or thirty days, according as the weather may suit. But if there is no immediate hurry for the bricks, the flues are placed about nine feet asunder, and the clamp left to burn off slowly. When the fire is set to the clamp, and it burns well, the ash-hole, being placed at the west end generally, the mouths are stopped with bricks, and clay laid against them; the outsides of the clamps are plastered with clay if the weather is at all precarious, or the fire burns furiously; and to the end against which addition is made to the clamp, skreens made of reeds worked into frames about six feet high, and sufficiently wide to be moved about with ease, are placed to keep off the weather, and against any particular side where wet is

most prevalent. On the top of the clamp a thick layer of breese is uniformly laid.

The excellency of bricks, says Mr. Malcolm, consists chiefly in the first and last operation; for bricks made of good earth, and well tempered, become solid and ponderous, and therefore will take up a longer time in drying and burning than our common bricks seem to require. It is also to be observed, that well drying of bricks, before they are burned, prevents cracking and crumbling in their burning; for when the bricks are too wet, the parts are prevented from adhering together. The best way of ordering the fire is, to make a gentle fire at first, and increase it by degrees, as the bricks grow harder. It has been said to give bricks additional strength if after burning they are steeped in water and burnt afresh.

The common computation is, that every acre of land will yield one million of bricks, in every foot in depth, including ashes, which are usually mixed with it. In general our fields are shallow, with a bottom of gravel, yet we think they will average nearly five feet, though we believe we have none that will run twelve or more feet, as about Kingsland; at least such is Mr. Malcolm's information on this subject. Among modern improvements, the patent bricks of Mr. Cartwright deserve some attention. These are formed with a groove down the middle, a little more than half the width of the side of the brick, leaving two shoulders, each of which will be nearly equal to one-half the groove. When they are laid in courses, the shoulders of the first course fit into the grooves of the second, and the shoulders of the second fall into the grooves of the first, thus forming an indented line of nearly equal divisions. The grooves, however, ought to be somewhat wider than the two adjoining shoulders, to allow for mortar, &c. The construction of these bricks is perfectly simple; but the principle will be preserved, in whatever form of indenture they may be made to lock into, or cramp each other. Brick walls, constructed upon this principle, require no bond timber, one universal bond connecting the whole building, which can neither crack nor bulge out without breaking through the bricks themselves. This invention is also particularly useful in the construction of arches; and when employed for this purpose, the shoulders of the bricks and the sides of the grooves should be radii of the circle, of which the intended arch is a segment. It is, however, recommended that if the arch be particularly flat, or applied in situations which do not admit of end walls, to have the shoulders dovetailed, to prevent the arch cracking across, or giving way edgeways. In forming an arch, the bricks must be coursed across the centre, and the grooved side of the bricks must face the workmen. The bricks may be either laid in mortar, or dry and the interstices filled up by pouring in lime putty, Paris plaster, or any other convenient material. The obvious advantages of arches constructed upon this principle, are, that the same centre, which, whatever be the breadth of the arch, may be in no case many feet wide, may be regularly shifted as the work proceeds; and, as they have no lateral pressure, they require LO abutments to prevent their expanding at the

foot, nor any weight upon the crown to prevent their springing up. They may be laid upon a common perpendicular wall, and if used in the construction of common buildings, they will not only preclude the necessity, and save the expense of timber, but will also afford an absolute security against the possibility of fire.

A M. Legressier has also lately announced an invention of the kind in the Archives des Decouvertes et des Inventions Nouvelles, pendant l'annee 1809. The principle is Mr. Cartwright's followed out to a greater extent. M. Legressier merely proposes, that the bricks should be formed in seven different moulds, according as they are to be placed in the middle or outside of the walls; in the bottom or on the top; in the arches or in corners; and, by the proper disposition of these bricks in the building, every pressure, either longitudinally or laterally, is resisted, in proportion to the strength of the indentures by which they are locked.

Fire-bricks are of different materials to common bricks; but made in the same way. The best clay for them is Stourbridge clay; and, instead of sand, it is usual to mix the clay with a quantity of old fire-bricks, crucibles, or glass pots, reduced to powder. The kinds of bricks made in this country, are principally placebricks, gray, and red stocks, marle facing bricks, and cutting bricks. The place bricks and stocks are used in common walling. The marles are made in the neighbourhood of London, and used in the outside of buildings; they are of a beautiful yellow color, hard, and well burnt, and in every respect superior to the stocks. The finest kind of marle and red bricks, are called cutting bricks, and are used in the arches over windows and doors, being rubbed to a centre, and gauged to a height. There is also a fine kind of white bricks made near Ipswich, which are used for facing, and sometimes brought to London for that purpose. In Sweden it is said to be customary, at some of the iron foundries, to cast the scoriæ into bricks, which they employ in constructing their furnaces. Any quantity of such bricks could then be produced by some of our large iron foundries; ard it is surprising that a recommendation upon this subject, long since given, has never been acted upon by them.

As articles of taxation, and furnishing a considerable revenue to Government, the size of bricks has been regulated by act of parliament. They must not be less than eight inches and a half long, two and a half thick, and four inches wide. But for specific purposes, they are allowed to be made of different sizes.

BRICKLAYING is the art of cementing bricks, by lime, or some other cement, so as to form one body. In London, bricklaying includes the business of walling, tiling, and paving with bricks or tiles; and it is sometimes united with plastering. In the country it is very common for the same person to exercise masonry, bricklaying, and plastering. This is of great antiquity.

Tools used by bricklayers, are, 1. The trowel, for taking up and spreading the mortar, in order to cement the bricks together, and for cutting them to any shape required. 2. The hammer, which is used to cut holes in brick walls. 3. The plumb rule, generally about fou" feet

&c.

long, and used with a plumb line, to carry the faces of walls perpendicularly. 4. The level from six to twelve feet long, used to try the level of works as it proceeds, more particularly window cills and wall plates. 5. The large square, for trying and setting out the sides of buildings at right angles, 6. The rod, for measuring, either five or ten feet long, and divided by notches on the edge, into as many feet, the last foot of which is divided into inches. 7. The jointing rule, eight or ten feet long, for running the joints of brickwork. 8. The jointer is made of steel, and shaped like the letter S; with this and the rule, the joints in brick-work are marked. 9. The compasses. They are used for traversing arches, 10. The raker, a piece of iron, bent like the letter Z, and pointed at both ends; its use is to pick or scrape decayed mortar out of joints in old walls to be replaced by new. 11. The hod, which consists of two boards put together at right angles, with a handle or leg, somewhat resembling the letter Y, fastened to that part where the two sides meet; one end of the trough is open and the other closed; its use is to carry mortar, bricks, stones, &c. up the ladders, on the shoulder, the handle serving to keep it steady while ascending, and to rest it upon when on the scaffolding. Some sand or dust is generally strewed over the inner surface when mortar is carried, to prevent its sticking. 12. The linepins. They are two iron pins for fastening and stretching the line, for the purpose of laying the courses level. 13. The rammer. When ground is of a loose kind this tool is used for compressing it, by beating on its surface. 14. The iron crow and pick-are are used for the purpose of breaking through walls; the crow-bar is used alone for raising large stones, or any other heavy bodies. 15. The grinding-stone, which is used for sharpening any of the tools. 16. The banker, a high bench of six to twelve feet long, two or three feet wide, and two feet eight inches high from the ground, and serves as a bench to rub bricks for arches or other work upon. 17. The camber-slip is a piece of wood of at least half an inch thick, with one of its edges curved, and rising about one inch in six feet; its use is for drawing the soffit lines of straight arches. If the other edge is curved, it should rise one half as much; this is used for drawing the upper side of straight arches, to allow for their settling. Some workmen prefer the upper side of the arch straight. When the lines are drawn the camber slip should be given to the carpenter to enable him to form the centre to the curve of the soffit. 18. The rubbing-stone, generally of a cylindric form, about twenty inches in diameter, fixed at one end of the banker. When the bricks are brought as near the shape as convenient, by the axe, they are by this rubbed smooth; it is also used for rubbing headers and stretchers, called rubbed returns. 19. The bedding-stone, formed of a piece of marble, about eighteen inches long, and eight or ten inches wide, with one fair side; its use being to try the rubbed sides of the brick, which must be first squared, in order to ry whether the surface of the brick is straight, so as to fit upon the leading skew-back, or leading end of the arch. 20. The small square, for trying the bedding of the bricks, and squaring

the soffits across the breadth of the bricks. 21. The bevel, for drawing the soffit line on the face of bricks. 22. The mould, used in giving form to the back and face of the brick, that it may have its thickness reduced to its proper taper, to which end one edge of the mould (which has a notch for every course of the arch), is brought close to the bed of the brick already squared, 23. The scribe, any piece of iron ground to a point, to mark by the edge of the rule or mould, 24. The tin-suw, for cutting the lines upon the bricks about one-eighth of an inch deep, that when the axe is used the edges may not spalter away. It is also used in cutting the soffit through its breadth, in the direction of the tapering lines, drawn on the face and back of the brick; the cut being made deeper on the face and back than in the middle of its thickness, for the purpose of entering the axe. The saw is likewise useful in cutting false joints, 25. The brick are is used for axing off the soffits of bricks to the scribes, and saw cuttings. The more care that is taken in axing, the less will be the labor of rubbing. 26. The tamplet is used in taking the length of the stretches and width of the header.-The last ten articles relate to the cutting of gauged arches.

The chopping block is any convenient piece of wood, placed so as to be three inches from the ground, supported either on legs or piers, and used for axing bricks upon. Its length must be according to the number of men that are to work at it.

The float stone is used to rub the curved surface of the bricks smooth; it is necessary to bring it as near as possible to the figure of the surface intended to be rubbed, before the operation is begun.

In laying bricks in the summer season, dip them into water, until they become saturated; and when the work is left for only one day, the walls should be as carefully covered as in the winter; for at such time the mortar sets too rapidly, and the necessary cohesion is destroyed. This evil is increased by the dust which hangs about bricks, more especially at this time of the year; and this last circumstance should operate as an additional motive for adopting the above expedient. While the injuries to which brickwork is liable, from frost, &c. is known to all, it is singular, that a point of equal, if not of superior importance, should be almost overlooked, or at least generally deemed too inconsiderable to merit attention.

In working up a wall, it will be proper not to work more than four or five feet at a time, for as all walls, immediately after building, shrink, the part which is first brought up will remain stationary, and when the adjoining part is raised to the same height, a shrinking or settling will take place, and separate the former from the latter, causing a crack, which will become more and more evident as the work proceeds. In carrying up any particular part, each side should be sloped off, to receive the bond of the adjoining work on the right and left. Nothing but absolute necessity can justify the work being carried higher, in any particular part, than one scaffold, for, wherever it is done, the workman is certainly answerable for all the evil which may arise from such palpable error.