hangings, &c. Where expense is not an object, two or three coats are applied, especially to marbling, each coat being well rubbed down to obtain an even surface and a high degres of polish. To restore the gloss of varnished graining, of marbling, or of varnished paper, the whole must be well cleaned, then sized afresh, and revarnished. But the original colour of the work can never be fully reproduced, as the varnish darkens by time. Bruns wick black varnish, a quick drying jet black, is used for grates, iron work, &c. Copal cabinet varnish, and a white, and a brown, hard varnish, and French polish, are used for cabinet-makers' work. A water flatting varnish renders paperhangings washable without imparting a gloss. These varnishes are all as made by Mander Brothers, Wolverhampton. 2276c. To clean varnished work, soap and water applied carefully with a sponge, and the use of warm woollen cloths to dry the work, is very efficacious. The steps of wooden staircases, painted, grained, and varnished, last a very long time, and neither dust nor dirt adhere so easily to such work as to paint. Real woods, especially wainscot, are prepared for receiving coats of varnish, by being first sized to prevent the rise of the grain which ensues when the slightest quantity of water touches it. When to be polished, they are well smudged over a short time previously with Russian tallow. A preparation called Lethicium is said to remove paint from wood in twenty minutes, doing away with the necessity for burning it off. A hypo-nitro kali has been introduced for the same purpose. 2276d. Sand paper, glass paper, emery paper, and emery cloth, of various degrees of fineness, are employed to rub down work to a surface. It is made by the pulverised material being placed in fine sieves, and by a gentle motion distributing it by hand over the paper or cloth prepared for its reception.

2276e. Stains, as substitutes for paint, the tints resembling oak, mahogany, rosewood, walnut, and satinwood, cause the natural grain of the deal on which they are applied to appear. The wood is then sized and varnished; their durability is stated to be at least three times that of paint in interior work, and only at half the cost. This is Stephen's preparation. Naylor's stain is said not to require sizing, and to stand exposure to the weather. Swinburn's Transparent staining and anti-dry-rot fluids are chemically prepared, and show the natural grain and feathery appearance of the wood. When sized and

the proper varnish used, they are said not to fade or blister by exposure to the weather. 2276f. Mander Brothers supply permanent wood stains in dry powder, which are instantly soluble in boiling water and perfectly fast in daylight; they are provided in boxes of 1 oz., 2 oz., 4 oz., 8 oz., and 16 oz. A pale copal varnish, or a dark hard-drying oak varnish, should follow in two coats, put on in a warmish room, free from dust. Kallkolitk is a new patent priming and stain; it is considered to be best used as a first coat of paint to wood, to impart durability to all oil colours, and that the paint does not blister. It is very useful to prepare walls for paperhangings.

2277. In the outside work and stairs, the process of sanding is frequently adopted. It is performed with fine sand thrown on the last coat of paint while wet. Cement work is generally coloured with its own cement mixed up with water. Roman cement, or black cement, as it is sometimes called, must have a wash or two; and while Portland cement is declared not to require any colouring, certain it is that in London not many years pass over before its dirty look urges a colouring or painting process. The process of painting the artificial cements, such as Parian, &c., is noticed in pars. 2251f, and 22734.

Gilding.

2277a. Gilling is of two kinds, burnished, and mat or dead, gilding. The former is seldom used in architectural decoration. The latter is done in oil-size on woodwork; in water-size on plastering. The gold leaf of various thicknesses, but generally about 200 of an inch, is called "single," "double," and "thirds," and of tints, is furnished in books of 25 leaves, each leaf being 3 by 3 inches, or in the book 18 inches and g of an inch superficial, covering about 1 foot of plain work. It should not be too thin nor have too much alloy. Gilding on metal is effected by first giving it a coat of paint or some other substance to prevent oxidation. Gold, absolutely pure and of extra thickness, was applied to the ironwork of the great tower at Westminster; and double gold leaf. pure, was used in the reading room of the British Museum. It has been stated, that if just before commencing to gild, each leaf of the book be slightly rubbed over with wax, sufficient only to cause the adhesion of the gold, that gilding in the open air, even in windy weather, may be done without the loss of a leaf, as the stickiness of the gold-size will overcome that of the wax, and no part be blown away, as is generally the case.

22776. A gold paint, patented by H. Bessemer, is now much used, which, by the highly improved manufacture of bronze powder, is greatly reduced in price in England, although very much is still purchased from the German dealers. As an impalpable metallic powder, its application to plaster, wood, &c., is effected by using a camel's hair brush, which is dipped into a little of the powder and rubbed up in a small portion of transparent gummy varnish, by which it adheres to the surface. For all outdoor works it requires to be varnished over for better preservation.

Paperhanging.

2277c. With painting is often connected the practice of paperhanging by the same artificer. The various sorts of paper used for lining walls may be described as follows: Block printed by hand, a process now seldom done. Machine printed, of great variety. Flocks, the pattern being formed by a wool ground to a fine powder and fixed to the paper by a sticky oil. Raised flocks; patent embossed flocks; imitation leather, of which the new Coriacene is an example. Woollams and Co. were the original makers of non-arsenical papers. They are also manufacturers of patent embossed flock papers, embossed imitation leather paper, and raised flock papers for painting over. Arsenical green in printed papers is considered injurious to health, from its flaking off in light particles, and floating in the air, when it is taken into the lungs while breathing. This colour may be at once detected by placing a few drops of ammonia on it, whereby the green will be changed into a deep blue.

2277d. The methods of manufacturing marble, granite, and wainscot wall papers, is well described in the Builder for 1865, p. 912, and which need not be here entered upon. 2277e. It may be mentioned that papers are printed 12 yards in length, such a length being called a piece, and 1 foot 8 inches wide; hence 1 vard in length contains 5 feet superficial; therefore, any number of superficial feet divided by 60 (the length 36 × 1 ft. 8 ins.) will give the number of pieces wanted for the work; 1 piece in 7 or 8 is allowed for cutting and waste to common papers, and any odd yards are allowed as a piece. French papers contain about 4 yards superficial per piece, being of various widths. In best papers this allowance for waste is not enough. Borders are 12 yards or 36 feet in each length, each being technically a dozen. A ream of printed paper of 20 quires of 24 sheets to the quire, is equal to 28 pieces of paper, or each piece contains 17 sheets. Satin papers should be hung over a lining paper. The paperhanger has to provide and hang materials required for covering damp walls.

2277f. Walls of rooms should always be stripped before the new paper be put up, a process usually attempted to be shirked, even when charged in the estimate. In bad common plasterer's work the setting coat often comes off in parts with the paper and has to be repaired. The walls are commonly prepared for papering by a coat of clearcole, or similar material, and for better work by rubbing down, &c.

2277g. Paperhangers' paste is made of flour, a little alum, and single size.

2277h. Testorium is stated to be a sanitary decoration for walls; it is a fine textured calico painted, with the patterns printed thereon. The dado filling is made in 22, 27, 30, 36, and 45 inches widths. The filling 22 inches wide is either in plain oil colours, or colours varnished, so that it can be washed with soap and water. The material is applied in the usual way as a paper; it checks the inroads of damp into a room. LincrustaWalton, formerly known as Muralis, the Sunbury wall decoration, is impermeable to moisture, and has other advantages. Muraline is one among the many washable papers. A Sanitary paper is made of non-absorbent materials, and being printed under a great pressure, the colouring is pressed into, and thoroughly incorporated with, the fibre of the paper. These papers are well adapted for sick rooms, and can be washed with cold water. The Duro-textile is of this character, and is made 24 inches wide. W. Cooke & Co.'s golden lustre silk paper hangings are stated to be free from all impurities.

Other Decorative Appliances and Processes.

2277i. Distemper and Fresco painting. Sgraffito, an ancient Italian process for external and internal plaster work. Pargetry, or modelling in wet plaster, as carried out in the half-timbered buildings of the 16th and 17th centuries. Modelled fibrous plaster work, for ceilings, &c. Marble mosaic floors. Tile paving. Artistic joinery in dados, doors, panelling, &c., in all woods. Chimneypieces in marble and wood. Real wood veneering in iieu of painting and paperhanging. Xylatechnigraphy, a new and permanent process 'for decorating woodwork in lieu of painting or graining. Radeke's compressed wood pulp. Stained glass and leaded lights. Embossed and painted modern leather, and Spanish leather, for walls, screens, &c. Tapestry, imitation painted or printed, for wall hangings, stuffs for curtains, furniture coverings, &c. Pyrographic woodwork (par. 2173g.). Marquetry (par. 2173g.). Colour decoration, applied to walls, continually fails. Mr. Heaton has invented Cloisonné mosaic, a material that will take colours on the principle of cloisonné work, which could be applied in panels 6 feet by 3 feet. It is a metal lining, filled in with a coloured material, and washable.

SECT. XIII.

VENTILATION OF BUILDINGS.

2278. Though this and the following section can scarcely be said to come legitimately under the heading of this chapter, the subjects are so intimately connected with each of the sections, and have been referred to occasionally in their description; and as, moreover, the architect is expected to make himself fully acquainted with these subjects, this place, then, appears to be suitable for the consideration of them.

2278a. Whether ventilation be left to chance, or whether any special apparatus be erected for the purpose, foul or vitiated air must be got rid of; while fresh air, adapted to the purposes of respiration, must be admitted in sufficient quantity, that is, at the rate of about 4 cubic feet per minute for each individual in the apartment. The force or impetus of the incoming air ought slightly to compress the air of the room and assist the efflux of the vitiated air; and this, in its turn, ought to be so heated as to have a certain amount of ascensional power. Mechanical means are sometimes necessary to expel or withdraw the air, such as fanners, bellows, pumps, &c.; but for general purposes it is more convenient, as well as economical, to trust to the natural method of getting rid of vitiated air; that is, by making certain ventilating tubes or openings at the highest point of the room, towards which the hot air tends to flow.

22786. Some authors have divided artificial ventilation into two branches, called plenum and vacuum. By the first, fresh air is forced into the interior of a building, and the vitiated air is allowed to escape by openings contrived for the purpose. By the second, vitiated air is drawn out of the building, and fresh air finds an entrance through channels adapted to the purpose.

2278c. As the velocity of a falling body in a second of time is known to be eight times the square root of the height of the descent, in decimals of a foot, so the velocity of discharge per second, through vent tubes or chimneys, may be briefly stated as equal to eight times the square root of the difference in height of any two columns of air, in decimals of a foot. This number, reduced one-fourth for friction, and the remainder multiplied by 60, will give the true velocity of efflux per minute. The area of the tube in feet or decimals of a foot, multiplied by this last number, will give the number of cubic feet of air discharged per minute. The height of a column of heated air must be calculated from the floor of the room to the top of the tube where it discharges into the open air. Where several vent tubes are employed, they must all be of the same vertical height, or the highest vent will prevent the efficient action of the lower ones, so that there might be a smaller discharge through two tubes than through one only.

2278d. When several openings are made above the level of the floor of a room, the highest one may be the only one capable of acting as an abduction tube, the other lower openings often serving as induction tubes, discharging cold air into the room instead of taking it out, and, in doing so, it may lower the temperature of the hot vitiated air and prevent it from escaping, thus not only causing the bad air to be breathed over again, but filling the room with unpleasant draughts. But if the highest abduction tube be too small to carry off the requisite qu ntity of hot air, the tube next below it in elevation at any part of the room will act as an abduction tube. If the lower openings (to be provided with sliding valves) for the admission of fresh air be too small in proportion to those for the escape of hot air, a current of cold air will descend through one part of the hot air tube, and the hot air will ascend through another part of the same tube. In order that ventilating tubes or openings may be effective, the lower opening for the admission of fresh air must be at least as large as the upper ones, and larger if possible. Tredgold recommended that the lower should be about double the area of the upper openings, and be so subdivided as to break the current. (Tomlinson, Warming and Ventilation, &c., 1850.)

2278e. It must be noted that all noxious gases do not rise, and therefore that in a few exceptional cases ventilation must be effected at the floor level. Taking atmospheric air at 60° Fahr., and under a pressure equal to 30 inches of mercury as 1,000, then hydrogen gas equals 6,926; nitrogenous miasma, about 975; olefiant gas, 978; sulphuretted hydrogen gas, 1,178; carbonic oxide, 957; and sulphurous acid, when anhydrous, 3,000. On the contrary, carburetted hydrogen gas, or marsh miasma, is as light as 555; and common coal gas ranges between 514 and 420. Thus above or below the temperature of 60° the conditions of the diffusion of gases vary in a marked manner, and it is on this account that the foul air of sewers, &c., exercises a more extended action laterally in hot weather, when it is able to diffuse itself more easily through an attenuated atmosphere, than in cold weather, when the greater density of the atmosphere, and the comparatively higher temperature of

the gases given off from the receptacles mentioned, enable the foul air to rise vertically with greater ease than to spread laterally. In a room, the carbonic acid emitted by the lights and by the breath of its occupants being of greater specific gravity than atmospheric air, would, at the ordinary temperature of the air, tend to accumulate in its lower strata; but the temperature of the products of respiration and of combustion is usually so much in excess of that of the air, that they are enabled to rise through it, and to accumulate in the upper portions of the enclosed room until some change in their temperature takes place. The foul state of the air in the lower portions of a pubic building on the day following a crowded meeting may be due to the change of temperature during the night, and the retention, by closed doors and windows, of the air so rendered impure. In 1865 General Morin read a piper to the Paris Academy of Sciences, again urging as a fundamental principle the exploded practice of drawing off vitiated air from the stratum nearest the floor, pure air being admitted near to the ceiling.

2278f. Our limited space will not permit us to do more than very briefly notice the chief principal methods of ventilation; the application of any one of them must be left o the ingenuity of the architect. He will find that all public buildings, and even all private houses, from the highest to the lowest class, must be spontaneously ventilated, for if any trouble be entailed, it will be neglected. The means for ventilation must be cheap, easily procurable, always in place, self-acting, and not liable to get out of order. Such an invention is the Arnott ventilator, when placed as close to the ceiling as practicable, forming a direct communication between the room and the chimney. The chimney has been made the means of securing a ventilation by a separate and rarified air channel. Thus, besides a mere channel left in the wall adjoining a flue, Doulton's patent combined smoke and air flues, of terra-cotta, for 12, 10, and 8-inch chimneys, are effective. Boyd's patent flue plates are similar in principle. Chowne's patent air-syphon, consisting of an inverted syphon tube, acts upon the principle of the air moving up the longer leg, and of entering and descending in the shorter leg, without the necessity for the application of artificial heat to the longer leg. This, however, does not appear to be always proved in practice, for whether the current in the longer leg be ascending or descending, depends chiefly upon differences of temperature within and without a building; but as the brickwork of chimneys often gets heated by the vicinity of the kitchen flue, or even by the sun shining upon it during the day, an ascending current is more likely to be sustained than a descending one, since brickwork will retain its heat for some hours.

2278g. The system adopted by Dr. Reid, at the House of Commons, was that of admitting air into a chamber underground, where it was (and is still) purified by being washed while passing through a stream of water, and then through canvas, whereby other impurities are extracted. It then rises to the floor of the apartment, which is pierced with many thousand holes, and passing through them is then further distributed by means of a hair-cloth, ascending towards the ceiling at about the rate of one foot per minute. This air is, in cold weather, warmed below; and in warm weather it is cooled with ice. Tre object is to keep the air in all seasons at a uniform temperature of 64°. The air is often cooler in the House than that outside it. From the ceiling it is carried rapidly away along a tunnel to feed the great furnace which creates this current of ventilation. The complaint is made that it carries with it from the floor the fine dust brought in by the members' feet, which, being inhaled, sometimes affects those in the House. The method adopted by Dr. Reid to warm and ventilate St. George's Hall, at Liverpool, is detailed in the Civil Engineer for 1864, page 136. The system employed from 1736 to about 1817 at the old House of Commons, which was effectively ventilated, was by a fan placed over it for extracting the heated air, its rate of working being dependent upon an attendant, who received his directions from a person within the House. The common revolving windguard placed at the top of a chimney to induce a suction, whereby the smoke may be drawn out, is of the same system; as is also Howarth's patent revolving Archimedean screw ventilator. One of the latest systems of effecting the regularity of working such fans or screws is by the aid of the high service water supply; a flow of water impinging upon the blades of a wheel turns the extracting fan, and the water is conveyed to a lower reservoir, to be used for domestic or other purposes.

2278h. The opposite system, that of air being forced into apartments by mechanical means, such as the fan driven by steam power, is practised with great success at che Reform Club House, the General Post Office, and many other buildings, public and private, and especially in factories. The fan is regulated to a velocity of between 80 and 100 feet per second. Dr. Van Hecke's system of warming and ventilating, as arranged at the new French hospitals, is effected by means of a 3 horse-power engine, working a fan, which drives the external air through long subterraneous channels into four warming apparatuses, whence it ascends into flues, which conduct it into all the wards, passing through regulating air gratings in the walls. In each ward are two or more escape flues carrying the vitiated air above the roofs.

2278i. The Blackman air propeller, for ventilating, cooling, and drying, has given good

results. One of 14 inches diameter, revolving 1,000 to 1,500 revolutions per minute, mored 1,500 to 2,500 cubic feet of air per minute. One of 24 inches diameter, revolving 500 to 900 per minute, moved 3,000 to 6,000 cubic feet of air. Another of 48 inches diameter, revolving 300 to 600 per minute, moved 13,500 to 30,000 cubic feet of air per minute.

2278k. The Boyle system of ventilation of workhouses and hospitals (1882), by selfacting air pump ventilator (perfected Oct. 1887) and the air inlet brackets, is used at St. George's Hospital for the extraction of the foul air and admission of fresh air, which is effected without draught, and is put forth as “the simplest, cheapest, and most efficient system of ventilation that is at present in existence."

22781. Another system prevails to some extent. The ventilation is combined with the method of warming, be it a church or other room devoted to a public purpose. This is effected by means of flues for extracting the air in the building being connected with the furnace of the apparatus. Such is the principle adopted by Messrs. Haden and Co., of Trowbridge. It has been in practice with success at the Royal Polytechnic Institution, London, for ventilating the large theatre since its erection in 1838. After the fire is once lighted, all its communications with the outer air are closed, and that of the extracting flue opened, which then supplies the fire with air brought down from the upper part of the theatre. Fresh air is admitted to the theatre only through the ordinary doors and openings.

2278m. As regards ventilation by windows, or the natural method, as it is called, as no system of making a sash working upon a horizontal axis, such as French casements, can wisely dispense with stay-bars, even when made to open and shut by means of a wheel and axle, our attention may be confined to lights hung on pulleys, or on hinges, or on centres. The first of these three classes is the common lifting sash. Wind-boards at top and bottom to prevent the effects of direct currents have been suggested; and machinery has been fitted to open both sashes simultaneously, so as to ensure the desired circulation of air through apertures at pleasure, or that shall not be altered without a key. This improvement has lately been successfully managed by the "patent counterbalance rack slips," which also do away with the use of lines, pulleys, and weights. In double windows, however, as in the lavatories at Middlesex Hospital, a roller has been placed between the two pairs of sashes, which move reciprocally, like the double bucket action; so that when the inner top sash is lowered the outer bottom one is raised, and the reverse; and the extension of this idea to the lights of water closets has been advocated. It has also been suggested that, in the usual windows, the horns of the upper sash styles should appear above the top rail, so that the window could never be tightly shut; but the benefit from this plan is confined to periods at which the window is not closed by shutters or by roller-blinds. The same objection applies to the use of such perforated glass and other contrivances as are mentioned in par. 2231a. It is stated that no draught is felt by the use of these inventions, as the air passing through the perforations is diffused equally and imperceptibly. We must notice that it will be found that the air is always passing into the apartment, and that when the wind blows towards the glass, the extra supply of air sent in is undoubtedly felt by the occupants, but sometimes not appreciated by them. Another method consists in the admittance of air either by a space left between the top bead (the horns, as before, stopping the sash from going home) and the head of the opening, or by such a space over the outer bead, to communicate with the box formed by the inside lining and the architrave or other dressing, the latter being either pierced with holes or detached slightly from its grounds. Another method much practised is to make the inside bead to the lower sash of a greater height than usual, say about two inches; thus when the sash is raised a litle and clears the meeting bar, fresh air will be admitted at the meeting bar and not admitted at the lower part. Old sashes may be so treated; even a bar of wood about three inches high, lined with baize, its length being the width between the sash reveals, can be put on the sill when the sash is raised, and the sash shut down upon it. This admits fresh air at the meeting bar sufficient to ventilate the room without draught.

2278n. Of the second class is the common hopper to a window, framed with or without side lights. In this are included all greenhouse sashes that are hung from the top, which may be made to open simultaneously by means of ratcheted stay-bars dropping into toothed wheels fixed on a continuous axis, worked by a wheel against an endless screw. When double windows are used, as in very cold climates, or when it is desirable to shut out noises, the upper portions of them should be made to open by the action of opening the inner window. This seheme has been adopted in the hospital of the Wieden suburb, and also in the Imperial stables, at Vienna, with success; its action is not described, but the outer window is presumed to be fixed, the heads of it forming a hopper, which is opened or shut by lowering or raising the inner window.

22780. To the third class belong nearly all the modern English patents for window ventilation, which consist of one or more planes working like a jalousie lath upon a hori