down, is continued till the roof is completely covered. The joints are then secured by filletting, which consists in cover ing all the meeting-joints with fillets of slate, bedded in glazier's putty, and screwed down through the whole into the rafters. The fillets are usually about three inches wide, and of a length proportionate to that of the slates, whose joints they have to cover. These fillets are solidly bedded in the putty, and their intersecting joints are lapped similar to those of the slates. The fillets being so laid, and secured by one in the middle of the fillet and one in each lap, ar next neatly pointed all round their edges with more putty, and then painted over with the colour of the slate. The hips and ridges of such slating are frequently covered by filets, which produces a very neat effect; but lead, which is not much dearer, is by far the best kind of covering for all hips and ridges. The patent slating may be laid so as to be per fectly water-tight, with an elevation of the rafters consider ably less than for any other slate or tile covering. The rise in each foot of length in the rafter is not required to be more than two inches, which, in a rafter of fifteen feet, will amount to only two feet six inches: a rise scarcely percep tible from the ground.

Slating is performed in several other ways, but the prin ciples already explained, embrace the most of them. Some workmen shape and lay their slates in a lozenge form. This kind of work consists in getting all the slates to an uniform size, of the shape of a geometrical square. When laid o the roof, which must be boarded, they are bonded and lapped as in common slating, observing only to let the elbow, or half of the square, appear above each slate that is next beneath it, and be regular in the courses all over the roof One nail or screw only can be used for such slating; hence it soon becomes dilapitated. It is commonly employed in places near to the eye, or where particular neatness is required.

It has been ascertained, that a slate one inch thick will, in an horizontal position, support as much, in weight, as five inches of Portland stone similarly suspended. Hence slates are now wrought and used in galleries, and other pur poses, where it is essential to have strength and lightnes combined.

Slates are also fashioned into chimney-pieces; but are incapable of receiving a polish like marble. It makes excellent skirtings of all descriptions, as well as casings to walls, where dilapidations, or great wear and tear are to be ex

pected. For these purposes, it is capable of being fixed with joints, equally as neat as wood: and may, if required, be painted over so as to appear like it. Stair-cases may also be executed in slate, which will produce a resemblance of marble.

MENSURATION OF PLASTERERS' AND SLATERS' WORK.

'Plasterers' work is executed by the yard square; and the dimensions are taken in feet and inches.

If a room consists of more than four quoins, the additional corners must be allowed at per foot run.

In measuring ceilings with ribs, the superficies must be taken for plain work; then an allowance must be made for each mitre, and the ribs must be valued at so much per foot run, according to the girth; or by the foot superficial, allowing moulding work.

In measuring common work the principal things to be observed are as follow:-first, to make deductions for chimneys, windows, and doors; secondly, to make deductions for rendering upon brick work, for doors and windows; thirdly, if the workman find materials for rendering between quarters, one-fifth must be added for quarters; but if workmanship only is found, the whole must be measured as whole work, because the workman could have performed the whole much sooner if there had been no quarters; fourthly, all mouldings in plaster work are measured by the foot superficial, the same as joiners, by girting over the mouldings with a line.

Slaters' work is measured and reduced into squares, containing 100 feet superficial. If in measuring the slating on a roof, it be hipped on all sides with a flat at top, and the plan of the building be rectangular, add the length and breadth of two adjoining sides of the eaves, and the length and breadth of two adjoining sides at the flat together, multiply the sum by the breadth of the slope, and the product will give the area of the space that is covered. Add the number of square feet produced, by multiplying the girts of the roof by the length of the slates at the eaves; to the area also, for the trouble of putting on the double row of slates, add the number of square feet produced by multiplying the length of the hips by one foot in breadth, and the sum will be the whole contents, and yield a compensation for the trouble and waste of materials. If there be no flats, add the two adjoining sides and twice the length of the ridge for the length; multiply the sum by the breadth of the slips, for

the arca of the space covered, and add the allowances as before.

Another plan is to allow in addition to the nett dimensions of the work, six inches for all the eaves, and four inches for the hips.

All faced work in slate skirting, stair-cases, galleries, &c. is charged by the foot superficial, without any addition.

PLUMBING,

Is the art of casting and working in lead, and using the same in the covering and for other purposes in building. To the plumber is also confided the pump-work, as well as the making and forming of cisterns and reservoirs, large or small closets, &c. for the purposes of domestic œconomy, The plumber does not use a great variety of tools, because the ductility of the metal upon which he operates does not require it.

The tools used, consist of an iron hammer, rather heavier than a carpenter's, with a short thick handle; two or three wooden mallets of different sizes; and a dressing and flatting tool.

This last is of beech, about eighteen inches long, and two inches square, planed smooth and flat on the under surface, rounded on the upper, and one of its ends tapered off round as a handle. With this tool he stretches out and flattens the sheet-lead, or dresses it to the shape required, using first the flat side, then the round one, as occasion may require.

The plumber has also occasion for a jack and trying plane, similar to that of the carpenter.

With this he reduces the edges of sheet-lead to a straight line, when the purposes to which it is to be applied re quire it.

Also a chalk line, wound upon a roller, for marking out the lead into such breadths as he may want.

His cutting tools consist of a variety of chisels and gouges as well as knives.

The latter of these are used for cutting the sheet lead int slips and pieces after it has been marked out by the chall

line.

Files of different sizes; ladles of three or four sizes, for melting the solder; and an iron instrument called grozing irons.

These grozing-irons are of several sizes, generally about twelve inches in length, tapered at both ends, the handle end being turned quite round, to allow of its being firmly held while in use: the other end is a bulb of a spindle, or spherical shape, of a size proportioned to the soldering intended to be executed. They are, when required for use, heated to redness.

The plumber's measuring rule is two feet in length, di vided into three equal parts of eight inches each; two of its legs are of box-wood, duodecimally divided; and the third consists of a piece of slow tempered steel, attached to one of the box legs by a pivot on which it turns, and falls, when not in use, into a groove cut in such leg for its reception. This steel leg can be passed into places where the others cannot enter; and it is also useful for occasionally removing the oxide or any other extraneous matters from the surface of the heated metal.

Scales and weights are also necessary; and he must be supplied with centre-bits of all sizes; and a stock to work them, for the purpose of making perforations in lead or wood, through which he may want to insert pipes, &c. Compasses, to strike circular pieces, to line or cover figures of that shape, are occasionally required.

Lead is obtained from ore, and, from its being generally combined with sulphur, it has been denominated "sulphuret." After the ore has been taken from its bed it is smelted, first being picked, in order to separate the unctuous and rich, or genuine ore from the stony matrix, and other impurities; the picked ore is then pounded under stampers worked by machinery, and afterwards washed to carry off the remainder of the matrix, which could not be separated in picking. It is next put into a reverberatory furnace, to be roasted; during which operation, it is repeatedly stirred, to facilitate the evaporation of the sulphur. When the surface begins to assume the appearance of a paste, it is covered with charcoal, and well shaken together: the fire is then increased, and the purified lead flows down on all sides into the basin of the furnace, whence it runs off into moulds prepared for its reception. The moulds are capable of receiving 154lbs. of lead each, and their contents, when cool, are, in the commercial world, called pigs.

Lead is of a bluish-white colour, and when newly melted, or cut, is quite bright; but it soon becomes tarnished on exposure to the atmosphere; assuming first a dirty grey colour, and afterwards becomes white. It is capable of

being hammered into very thin plates, and may be drawn into wire; but its tenacity is very inferior to that of other metals; for a leaden wire, the hundred and twentieth part of an inch in diameter, is only capable of supporting about 18lb. without breaking. Lead, next to tin, is the most fusible of all metals; and if a stronger heat be applied, it boils and evaporates. If cooled slowly, it crystallizes. The change of its external colour is owing to its gradual combination with oxygen, which converts its exterior sur face into an oxyd. This outward crust, however, preserves the rest of the metal for a long time, as the air can pere trate but very slowly.

Lead is not acted upon immediately by water, though that element greatly facilitates the action of the air upon it: for it is known that, when lead is exposed to the atmosphere, and kept constantly wet, the process of oxidation takes place much more rapidly than it does under other circum stances: hence the white crust that is to be observed on the sides of leaden vessels containing water, just at the place where the surface of the water terminates.

Lead is purchased by plumbers, in pigs, and they reduce it into sheets or pipes, as they have occasion. Of sheet-lead they have two kinds, cast and milled. The former is used for covering flat roofs of buildings, laying of terraces, forming gutters, lining reservoirs, &c.; and the latter, which is very thin, for covering the hips and ridges of roofs. This last they do not manufacture themselves, but purchase it of the lead merchants, ready prepared.

For the casting of sheet lead, a copper is provided, and well fixed in masonry, at the upper end of the workshop, near the mould or casting table, which consists of strong deal boards, well jointed together, and bound with bars of iron at the ends. The sides of this table, of which the shape is a parallelogram, vary in size from four to six feet in width, and from 16 to 18 feet and upwards in length, and are guarded by a frame or edging of wood, 3 inches thick, and 4 or 5 inches higher than the interior surface, called the shafts, This table is fixed upon firm legs, strongly framed together, about 6 or 7 inches lower than the top of the copper. At the upper end of the mould, nearest the copper, is a box, called the pan, which is adapted in its length to the breadth of the table, having at its bottom a long horizontal slit, from which the heated metal is to issue, when it has been poured in from the copper. This box moves upon rollers along the surface of the rim of the table, and is put in mo