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nine inches thick, laid over the whole surface

Prevention of Bamp in Buildings. of the house; a thin sheet of lead between the

concrete and piles would be an additional security; and in such buildings as palaces, a DAMP in buildings arises from the hygrometric thin layer of asphalte might be laid over the properties of all the materials commonly used concrete. In the dwellings of the poor, howin building, even granite imbibing moisture ever, brick piers, even without the cement, from a humid atmosphere; the walls of houses half a brick wide, and one course high, might will therefore absorb the moisture from the be used with advantage; and if the floor were soil with which they are in contact, and from of stone paving, bricks laid under every joint the rain, which is driven against the walls by would keep the floors tolerably free from wind, or splashes against them from the damp. Channels, about the size of a brick, ground, or which drips from the tops of walls and furnished with iron gratings, should be which are unprovided with gutters, or accu- left in walls to admit air to the floors: these mulates at the lower ends of rain-pipes which might be closed by a sliding plate in the skirthave no shoes. The extent of the mischief ing when required, as in cold and rainy The floors of a lowermost story arising from the sources which we have enuon the should not be covered with any impervious merated depends in some measure nature of the soil and materials, the modes of fabric, such as oilcloth, as the moist air which construction, and the aspect of the building. always rises through the joints of the boards Paving around a building affects its dryness from the ground, if intercepted, will speedily by carrying off the surface water, and the con- rot both boarding and cloth. Eave gutters tiguity of sewers or drains has a similarly and standard pipes with shoes are indispensable, as the water from eaves and waterbeneficial effect. shoots is driven against the wall, which is thereby saturated; and the want of a shoe. occasions an injurious accumulation of water at the foot of the wall.

weather.

Clocks.

The method of averting the inroads of damp consists in making the foundations rest on a layer of concrete, about a foot thick; and in interposing a sheet of thin lead between the courses of the masonry, or brickwork, at the level of the ground; or instead, a layer of bitumen thinly spread, or a double course of This lead, bitumen, or slate set in cement. slate, is intended to prevent the damp from rising from the footings, while the absorption THE introduction of clocks into Great Britain of moisture from the ground next the outer took place about the year 1288, and, in 1326, face of the wall is provided against by facing Wallingford is said to have constructed a clock the ground with stone to a depth of two or regulated by a balance, which was put in three feet; the facing to be either close to the motion by weights, but whose action was exwall or separated from it by a narrow space. tremely irregular. The great improvement of The most effectual preservative of the outer the pendulum does not appear to have taken face of a wall from the adjacent soil, lies in place until about the middle of the seventeenth making a wide space, say three or four feet, century, and the name of the person who first About 1641 Richard Harris is between the wall and the ground facing, which employed it for this purpose is not accurately may serve as a passage round the building, ascertained. and afford access to cellars outside, or the said to have constructed a pendulum clock for space may be formed into areas, presenting a St. Paul's church, Covent-garden; however, as convex wall to the earth, and abutting against Huygens, in 1658, was the first who explained the wall at the springing. Openings must be accurately the motion of the pendulum, the The application of the made through these abutments for the areas to chief merit of its application to clocks may be communicate with each other, and to diminish attributed to him. the surfaces in contact. To effect the due cir- spiral spring to the balance is due to Hooke in culation of air, perforations should be made 1658; and the introduction of the compenthrough the walls of the house near the foun-sating mercurial pendulum by Graham, in 1715, dation, and channels should also be made for the external air to communicate with that within the areas, which are covered over with slabs of stone to prevent the entrance of water. Immediately above these covering slabs, which should not be below the surface of the ground if it can be avoided, the wall should be faced with cement. The plastering should not be applied immediately on the walls, but on laths nailed to long narrow slips of wood The air secured to the wall by holdfasts.

was the next great step in improvement; by means of this valuable invention, the unequal expansion and contraction of the pendulum from change of temperature, which rendered impracticable the accurate measurement of time, was obviated. Graham also suggested the idea of employing different metals, having different properties of expansion, so that the one should neutralise the other; his idea was afterwards carried out by Harrison, in the construction of the gridiron pendulum. For the going fusee, space thus left between the plaster and the the compensation curb, and other improvewall prevents the communication of the dampments, he received a Parliamentary reward. from the wall to the plaster. The wooden floors or stone slabs forming the lower storey should not be in contact with the ground; they should be supported by piers or sleeper walls, resting on a stratum of concrete, six to

The scapement, which communicates the sustaining force to the pendulum or balance, demands the greatest skill and accuracy, and various forms have been attempted; amongst others may be mentioned the original scape

The art of clock or watchmaking, termed horology, may be said to be principally composed of four parts. 1. The moving power, which is generally a weight for clocks or fixed time-keepers, and a spring for watches or 3 We cannot undertake to return Rejected Commu

walls and the wall which unites them, and two sometimes slung upon chains, &c., in which internal obtuse angles, formed by the two pro- case it is called à suspension bridge (see

DECORATOR'S ASSISTANT, page 59, ante) or chain bridge. There are also some formed of wire.

TO BRIDGE OVER, a term employed when a piece of timber is placed transversely over any number of parallel boards or timbers.

BRIDGE-STONE, a horizontally laid stone, extending over an area from the pavement to the entrance door of a house, without being supported by an arch.

BROKEN COLOURS (in painting), combinations of the primary colours and their compounds.

BROOCH, a painting of one colour only.
BUFFET, a cupboard for plate, &c.
BULKER, a Licolnshire term for a

beam or

Linseed Oil.

THE clearest and best oil of this description is that procured by means of the cold expression of the seeds of the common flax plant, and denominated in commerce "cold drawn linbruised seeds in the oil-mill, makes the extract seed oil;" the other method, of roasting the of a brownish-yellow colour, and extremely liable to become rancid.

This oil is extensively used as a fixed vehicle in oil-painting, and is also employed in varnish-making; but it has the great demerit of darkening quickly, which is not so much the case with poppy or nut oil. Another evil, which is shared by poppy oil, consists in its great degree of fattiness, which hinders its drying; but this is, however, materially got rid of by the following plan:-Take of white vitriol, three parts; litharge, twelve parts; and let them be reduced to as fine a powder as possible; then mix with thirty-two parts of the oil, and place the whole over a fire sufficiently brisk to keep the oil slightly boiling. Let it continue in this manner until no more scum is thrown up by the oil; then remove the vessel, and place it in a cool situation for about three BUST, a sculpture of the head, breast, and hours, when a fatty sediment will be formed at shoulders.

rafter.

BULL'S-EYE OF BULLOCK'S-EYE, a round pane of glass let into a roof or wall.

BUNDLE PILLAR (in Gothic architecture), a column having a number of small pillars round its circumference.

the bottom. Now carefully pour off the oil at the top into wide-mouthed bottles, where it must be left until it has perfectly cleared itself, when it will be found to possess the requisite drying quality.

In some cases, when the fire is not equalised during the process of boiling, the colour of the oil changes to such a degree as to make it totally unfit for paintings requiring great nicety and harmony in the tones of colour. This may be prevented by placing the pounded litharge and vitriol in a bag; but in this case the former must be doubled in quantity. The bag also requires to be suspended by means of packthread to a stick crossing the mouth of the vessel, so as to keep the bag at the distance of an inch from the bottom. This method is somewhat slower than the first-mentioned one.

It is a commonly mistaken notion that linseed oil will stand in any situation; such, however, is not the fact, as the sun and rain soon destroy it, and the work has to be repeated.

Linseed oil is sometimes mixed with the oil of turpentine, and others of a volatile nature, a very injurious adulteration with regard to varnishing. It can, however, be always readily detected by dropping a small portion on a sheet of paper and holding it over a lighted candle, when the volatile oil will fly off before the paper is consumed, leaving the linseed behind.

NEW METHOD OF CLEANSING THE LENSES OF TELESCOPES.-The ordinary method of cleansing the object lens of a telescope is by means of spirit of wine. This process produces, in a few minutes, a remarkable opacity in the glass, which much impairs its transparency, and renders the operation of wiping necessary, as By long boiling, linseed oil becomes of a often as the instrument is used. M. Sivet dark brown colour, tenacious, and thickened, announces as the result of his experiments in which state it is employed in the manufac upon the subject, that the use of sublimed sul-ture of printers' ink and, by still longer phur, with animal charcoal, in the proportion boiling, it becomes black, almost solid, and of two of the former to one of the latter, is elastically tenacious, like Indian rubber, in attended with the most desirable results-viz., which state it serves for bird-lime. the most effectual cleansing of the lens, at the same time preserving its perfect transparency.

* Linseed yields about 22 per cent. of oil.