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 adjoining shoulders, to allow for the mortar or cement. When the course is laid on, the shoulders of the bricks, which compose it, will fall into 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 nor 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 will 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 a 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 heap 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·

lel to the front, there can be no lap where the stones run of an equal depth in the thickness of the wall. It is also advantageous to the stability of the wall to select the stones, so that a thicker and a thinner one may succeed each other alternately. In each course of ashlar facing, either with rubble masonry, or brick backing, thorough-stones should occasionally be introduced, and their number be in proportion to the length of the course. In every succeeding course, the thorough stones should be placed in the middle of every two thorough-stones in the course below; and this disposition of bonds should be punctually attended to in all cases where the courses are of any great length. Some masons, in order to prove that they have introduced sufficient bonds into their work, choose thorough-stones of a greater length than the thickness of the wall, and afterwards cut off the ends; but this is far from an eligible plan, as the wall is not only subject to be shaken, but the stone is itself apt to split. In every pier, between windows and other apertures, every alternate jamb-stone ought to go through the wall with its bed perfectly level. When the jamb-stones are of one entire height, as is frequently the case when architraves are wrought upon them, upon the lintel crowning them, and upon the stones at the ends of the courses of the pier which are adjacent to the architravejamb, every alternate stone ought to be a thorough-stone: and if the piers between the apertures be very narrow, no other bond-stone is required; but where the piers are wide, the number of bond-stones are proportioned to the space. Bond-stones must be particularly attended to in all long courses below and above windows.

All vertical joints, after receding about an inch with a close joint, should widen gradually to the back, thereby forming hollow spaces of a wedge-like figure, for the reception of mortar, rubble, &c. The adjoining stones should have their beds and vertical joints filled, from the face to about three quarters of an inch inwards, with oil and putty, and the rest of the beds must be filled with well-tempered mortar. Putty cement will stand longer than most stones, and will even remain. permanent when the stone itself is mutilated. All walls cemented with oil-putty, at first look unsightly; but this disagreeable effect ceases in a year or less, when, if care has been taken to make the colour of the putty suitable to that of the stone, the joints will hardly be perceptible.

In selecting ashlar, the mason should take care that each stone invariably lays on its natural bed; as from ca 'eless

ness in this particular, the stones frequently flush at the joints, and sooner admit the corrosive power of the atmosphere to take effect.

It ought also to be observed, that, in building walls, or insulated pillars of small horizontal dimensions, every stone should have its bed perfectly level, and be without any concavity in the middle; because, if the beds are concave, the joints will most probably flush when the pillars begin to sustain the weight of the building. Care should also be taken, that every course of masonry in such piers be of one stone.

Having thus given to the practical mason an outline of the subject of walling, we will proceed to the consideration of the more difficult branches of the art, that of constructing arches and vaults.

DEFINITIONS.

An arch, in masonry, is that part of a building which is suspended over a given plane, supported only at its extremities, and concave towards the plane.

The upper surface of an arch is called the extrados; and the under surface, or that which is opposite the plan, the intrados.

The supports of an arch are called the spring walls.

The springing lines, are those common to the supports and the intrados; or the line which forms the intersection of the arch with the surface of the wall which supports it. The chord, or span, is a line extending from one springing line to the opposite one.

Section of the hollow of the arch, is a vertical plane, supposed to be contained by the span and the intrados.

The height, or rise of the arch, is a line drawn at right angles from the middle of the chord, or spanning line, to the intrados.

The crown of the arch is that part which the extremity of the perpendicular touches.

The haunches, or flanks, of the arch, are those parts of the curve between the crown and the springing line.

When the base of the section, or spanning line, is parallel to the horizon, the section will consist of two equal and similar parts, so that when one is applied to the other, they will be found to coincide.

Arches are variously named according to the figure of the section of a solid that would fill the void, as circular, ellip ·