Fig 91 -Wood casement and Frame, the casement to open Inward.

A. horisontal section of Jamb and stile; B, vertical section of sill and bot lam rail. cc. grooves to collect water driven along Joints between casement and frame ; D, holes to convey water from grooves to sill outside.

Fig. 92 - Wood casement and Frame, the casement to open outward. A,horizontal section of Jamb and stite; B, vertical section of sill and.

Fig. 93 -Meeting-stiles of French Casement.

Plate V.

DETAILS OF COMBINED SASH-AND-CASEMENT WINDOW.

Fig. 94. - The N.A. P. Window casement. Inward and outward opening. (one fourth of full size).

A, groove to receive brass weather-rod, b, brass rod, which automatically rises from the position shown (travelling up the necks of two screws), as the casement is swung either inwards or outwards; c, position of water-bar when the casement la in ordinary use; P. condensation-channel; R, two outlets (from D) at ½ the width of casement; r, outlet (from weather-channel on top of sill) In centre of casement; G, throat to receive rain-water, but single or double rebates may be subetituted If desired; H, groove (for a height equal to the width of the casement) to receive the water-bar when in the vertical position which it occupies while the casement is passed through the frame; I, patent N.A.P. double knuckle hinge.

Metal casements are now frequently used, wrought-iron being most common but gun-metal being adopted in the very best work. They can be obtained in a great variety of sections, from simple L-iron to complicated arrangements like that shown in Fig. 95.

The sill, jambs, and head of the opening must be specially prepared to suit the section of casement-frame which may be adopted. Metal casements are expensive, but they do not take up much room, and they are durable if regularly painted. Gun-metal, of course, does not require painting.

Fig. 95 - Wrought-iron Casement and Frame A, horizontal section of casement and Jamb; a, vertical section of casement and sill..

Mention has already been made of the coldness of windows in winter, and of the improvement in this respeet which may be gained by means of double windows, or double panes of glass with a small air-space between. Both devices reduce the sound transmitted through the windows, and this is certainly a great blessing in towns. When double windows are used, the outer window may be a sash-window, and the inner one a casement (generally hung folding and opening inward). Double panes are, however, a better protection against changes of temperature: Peclet's tests showed that, counting the loss of heat through a single sheet of glass as 1, the loss through two sheets 2.8 inches apart is .6, 2 indies apart 55, and .8 of an inch apart only '47. The construction of windows to receive double sheets of glass presents little or no difficulty; the wood must simply be rebated on both sides, and the outer sheet may be secured with putty in the usual way, while the inner may be kept in position by a small bead sprigged to the framing.

Glass is a very important part of a window. It is a comprehensive term, including sheet-glass, rough and polished plate-glass, patent rolled plate-glass in a great variety of tints; and patterns, ground and obscured glass, enamelled sheet-and plate-glass, etc Polished plate-glass is undoubtedly the best for most purposes, the most common thickness for ordinary house-windows being ¼-inch.

Sheet-glass is of various qualities, and is sorted into thicknesses, usually known as 15-ounce, 21-ounce, 26-ounce, 32-ounce, and 36-ounce. The kind of glass to be used in any window or borrowed light will depend on the purpose it has to sen If the window is for prospect and abundance of light, then sheet-glass or (Utter) plate-glass must be used. If, however, the prospect is obnoxious, some other kind of glass is desirable, such as patent rolled plate or leaded lights. It must not be forgotten, however, that every process which renders glass less clear to the eye, renders it also less transparent to light. Sir Douglas Galton give-the following results of experiments: -

Polished British plate-glass, ¼-inch thick, intercepted 13 per cent of the light. 36-ounce sheet-glass

Cast plate-glass, ¼-inch thick, „ 30

Rolled plate-glass,1 4 corrugations in an inch, „ 53 „

These figures may be supplemented by others dealing with coloured glass as well as with plain: -

1 This would be about ¼ inch thick. G. L. S. 2 This would be about ½ inch thick. G. L S. 3From Praktichen Gewerbehygiene, edited by Dr. H. Albrecht Berlin, 1896.

Interception Of Light By Glass

Doubtless the green and red colours were very strong. The "ordinary window glass" must have been extremely thin; it would have been better if the thiek-ness of the glass had been given in each case.