shallow pits, and subjecting it to 'the tread of men and oxen; but this method has of late been superseded by the clay or pug mill, which is a very eligible, though simple machine.

The clay or pug mill consists of a large vertical cone, having strong knives with a spiral arrangement and inclination fixed on its internal surface. Passing through the centre, and terminating in a pivot at the bottom, is a strong perpendicular shaft with similar radiating knives, so that the knives by the revolution of the shaft, cut, separate, and purify the clay, till it be reduced to a homogeneous paste, which passes through an orifice at the bottom into a receiver placed for that purpose. The clay is taken from the receiver to the moulder's bench, and is, either by a lad or a woman, cut into pieces somewhat larger than the mould, and passed on to the moulder, who works it into a mould, previously dipped in sand, and strikes off the superfluous parts with a flat smooth piece of wood. In this country the mould used is about ten inches in length, and five inches in breadth, and the bricks when burnt are about nine inches long, four and a half inches broad, and two and a half inches, thick. The degree of shringing, however, is various, according to the temper and purity of the clay, and the degree of heat attained in the burning. A handy moulder is calculated to mould from about 5000 to 7000 per day. From the moulder's bench the bricks are carried to the hack, and arranged somewhat diagonally, one above the other, and two edgewise across, with a passage between the heads of each for the admission of air, till they be eight bricks in height. They are then left to dry. The time they take ere they rerequire shifting depends entirely upon the weather, which when fine will be but a few days: they are then turned and re-set wider apart, and in six or eight days are ready for the clamp or kiln.

Clamps are generally used in the vicinity of London. They are made of the bricks to be burnt, and are commonly of an oblong form. The foundation is made either with the driest of the bricks just made, or with the cammonest kind of brick, called place bricks. The bricks to be burnt are arranged tier upon tier as high as the clamp is intended to be, and a stratum of breeze or cinders to the depth of two or three inches is strewed between each layer of bricks, and the whole is finally covered with a thick stratum of breeze. At the west end of the clamp a perpendicular fire-place of about three feet in height is constructed, and flues are formed

by arching the bricks over so as to leave a space of about a brick in width. The flues run straight through the clamp, and are filled with a mixture of coals, wood, and breeze, which are pressed closely together. If the bricks are required to be burnt off quickly, which can be accomplished in the space of from twenty to thirty days according to the state of the weather, the flues must not exceed six feet distance apart; but if there is no urgent demand, the flues need not be nearer than nine feet, and the clamp may be allowed to burn slowly.

Coke has been recommended as a more suitable fuel for bricks than either coal or wood, as the dimensions of the flues and the stratum of the fuel are not required to be so great, which, since the measurement of the clamp has been restricted to certain limits by the interference of the legis lature, is a point of some consideration; besides, the heat arising from the coke is more uniform and more intense than what is produced by the other materials, so that the burning of the bricks is more likely to be perfect throughout. The saving which is thus produced may be calculated at about 32 per cent.

Kilns are also in common use, and are in many respects preferable to the clamp, as less waste arises, less fuel is consumed, and the bricks are sooner burnt. A kiln will burn about 20,000 bricks at a time. The walls of a kiln are about a brick and a half thick, and incline inwards towards the top, so that the area of the upper part is not more than 114 square feet. The bricks are set on flat arches, with holes left between them, resembling lattice-work; and, when the kiln is completed, are they covered with pieces of broken bricks and tiles, and some wood is kindled and put in to dry them gradually. When sufficiently dried, which is known by the smoke changing from a dark to a light transparent colour, the mouths of the kiln are stopped with pieces of brick, called shinlog, piled one upon another, and closed over with wet brick-earth. The shinlogs are carried so high as just to leave room for one faggot to be thrust into the kiln at a time, and when the brush-wood, furze, heath, faggots, &c. are put in, the fire is kindled, and the burning of the kiln commences. The fire is kept up till the arches assume a white appearance, and the flames appear through the top of the kiln; upon which the fire is allowed to slacken, and the kiln to cool by degrees. This process of alternately heating and slacking the kiln is continued till the bricks are thoroughly burnt, which, in

general, is in the space of forty-eight hours. The practice of steeping bricks in water after they have been burned, and then burning them again, has the effect of considerably improving the quality.

Bricks are of several kinds, the most usual of which are marls, stocks, and place bricks; but there is little difference in the mode of manufacturing them, except that great care is taken in preparing and tempering the marls.

The finest marls, called firsts, are selected for the arches of doorways, &c. and are rubbed to their proper form and dimensions: and the next best, called seconds, for the principal fronts. The colour, a light yellow, added to the smooth texture, and superior durability of the marls, give them the precedence of the other descriptions of brick.

Grey stocks are somewhat like the seconds, but of inferior quality.

Place bricks, sometimes called pickings, sandal, or samel bricks, are such as from being the outermost in the clamp or kiln, have not been thoroughly burned, and are, in consequence, soft, of uneven texture, and of a red colour.

There are also burrs or clinkers, arising from the bricks being too violently burned, and sometimes several bricks are found run together in the kiln. They derive their colour from the nature of the soil of which they are composed, which, in general, is very pure. The best kind are used as cutting bricks, and are called red rubbers. In old buildings they are very frequently to be seen ground to a fine smooth surface, and set in putty instead of mortar, as ornaments over arches, windows, door-ways, &c.; but though there are many beautiful specimens of red brick-work, yet these bricks cannot be judiciously used for the front walls of buildings. This objection arises from the colour being too heavy, and from its conveying to the mind, in the summer months, an unpleasant idea of heat; to which may be added, that as the fronts of the buildings have a greater or less proportion of stone and painted wood-work, the contrast in the colours is altogether injudicious. The colour of grey stocks, on the contrary, assimilates so much with the stones and paint, that they have obtained, in and near London, universal preference.

At the village of Hedgerley, near Windsor, red bricks are made which will stand the greatest heat: they are called Windsor bricks.

Bricks used for paving, are generally about an inch and a half in breadth; and, beside these, there are paving tiles,

which are made of a stronger clay, and are of a red colour. The largest are about twelve inches square, and one inch and a half thick: the next, though called ten-inch tiles, are about nine inches square, and one inch and a quarter thick. About the year 1795, a patent was obtained by Mr. Cartwright, for an improved system of making bricks, of which the following extract will furnish the reader with all necessary information.

"Imagine a common brick, with a groove or rabate on each side down the middle, rather more than half the width of the side of the brick; a shoulder will thus be left on either side of the groove, each of which will be nearly equal to one quarter of the width of the side of the brick, or to one half of the groove or rebate. A course of these bricks being laid shoulder to shoulder, they will form an indented line of nearly equal divisions, the grooves or rebates being somewhat wider than the aljoining shoulders, to allow for the mortar or cement. When the course is laid on, the shoulders of the bricks, which compose it, will fall inte grooves of the first course, and the shoulders of the first course, will fit into the grooves or rabates of the second, and so with every succeeding course. Buildings constructed with this kind of brick, will require no bond timbers, as an universal bond runs through the whole building, and holds all the parts together; the walls of which will neither crack not bilge without breaking through themselves. When bricks of this construction are used for arches, the sides of the grooves should form the radii of the circle, of which the intended arch is a segment; yet if the circle be very large, the difference of the width at the top and bottom wil be so very trifling, as to render a minute attention to this scarcely if at all necessary. In arch-work, the bricks may either be laid in mortar, or dry, and the interstices afterwards filled up by pouring in lime, putty, plaster of Paris, &c. Arches upon this principle, having any lateral pressure, can neither expand at the foot, nor spring at the crown, consequently they want no abutments, requiring only perpendicular walls to be let into, or to rest upon; neither will they want any superincumbent weight on the crown to prevent their springing up. The centres also may be struck immediately, so that the same centre, which never need be many feet wide, may be regularly shifted as the work proceeds. But the most striking advantage attending this invention is, the security it affords against the ravages of fire; for, from the peculiar properties of this kind of arch, requiring no abutments, it may be laid upon, or let into common walls, no stronger than what is required for timbers so as to admit of brick floorings."

Having said thus much on the laying of the foundation, the mixing of the mortar, and the manufacture of the brick, we shall next proceed to treat on the principles of the art of masonry, as practised in the present day.

MASONRY,

Is the art of cutting stones, and building them into mass, so as to form the regular surfaces which are required in the construction of an edifice.

The chief business of the mason is to prepare the stones, make the mortar, raise the wall with the necessary breaks, projections, arches, apertures, &c., and to construct the vaults, &c. as indicated by the design.

A wall built of unhewn stone, whether it be built with mortar or otherwise, is called a rubble wall. Rubble work is of two kinds, coursed and uncoursed. In coursed rubble the stones are gauged and dressed by the hammer, and thrown into different heaps, each beap containing stones of equal thickness; and the masonry, which may be of different thicknesses, is laid in horizontal courses. In uncoursed rubble the stones are placed promiscuously in the wall, without any attention being paid to the placing them in courses; and the only preparation the stones undergo, is that of knocking off the sharp angles with the thick end of a tool called a scabling hammer. Walls are generally built with an ashlar facing of fine stone, averaging about four or five inches in thickness, and backed with rubble work or brick.

Walls backed with brick or uncoursed rubble, are liable to become convex on the outside, from the great number of joints, and the difficulty of placing the mortar, which shrinks in proportion to the quantity, in equal portions, in each joint; consequently, walls of this description are much inferior to those where the facing and backing are built of the same material, and with equal care, even though both of the sides be uncoursed. When the outside of a wall is faced with ashlar, and the inside is coursed rubble, the courses of the backing should be as high as possible, and set within beds of mortar. Coursed rubble and brick backings are favourable for the insertion of bond timber; but, in good masonry, wooden bonds should never be in continued lengths, as in case of either fire or rot the wood will perish, and the masonry will, by being reduced, be liable to bend at the place where the bond was inserted.

When timber is to be inserted into walls for the purposes of fastening buttons for plastering, or skirting, &c., the pieces of timber ought to be so disposed that the ends of the pieces be in a line with the wall.

In a wall faced with ashlar, the stones are generally about 2 feet or 2 feet in length, 12 inches in height, and 8 inches in thickness. It is a very good plan to incline the back of each stone, to make all the backs thus inclined run in the same direction, which gives a small degree of lap in the setting of the next course; whereas, if the backs are paral·