The danger is thus obviated that the combustion should be too intense if the furnace-door is inadvertently left open.

Fig. 517 View of Exterior of Korting's Boiler.

Fig. 517-View of Exterior of Korting's Boiler.

C.Furnace-door, D,patent grate; F,fuel-hopper; R, draught-regulator; M, pressure-gauge, W,water-gauge; H, draw-off cock; V,connection of boiler with water-tube grate, and condensed-water return pipe; ST,stand; 16 feet high; valve for clearing safety-pipe of water.

"The advantages of the arrangements for firing, as roughly sketched, are that the combustion of the fuel is exceedingly perfect, and the generation of smoke so small that the problem of smoke-prevention is fully solved; the fuel, which is contained inside the water-tubes, has no direct contact with the brickwork, and repairing or renewal of the boiler-setting is rendered almost unnecessary; and lastly, accumulation of clinker does not form, as the hot clinker suddenly contracts on coming in contact with the comparatively cool surface of the water-tubes, breaking into small pieces, which readily find their way into the ash-pit.

Fig 518.   Section of Kurting's Boiler.

Fig 518. - Section of Kurting's Boiler.

"The filling-hopper f can be made of any size to suit the kind of fuel in use, and may be sufficiently large to contain two days' supply of fuel. We are making these boilers in ten sizes of from 40 to 400 square feet of heating-surface, and are prepared to make larger ones if required The attendance required for one of these large boilers is naturally much less than is needed in other systems of heating, where several smaller boilers are used. The work of the attendant is confined to re-filling the hopper F with fuel, which is only necessary at long intervals, and to removing clinker and ash two or three times a day, so that we may claim to have reduced the attendance to a minimum.

"The maintenance of a constant pressure is of special importance with low-pressure steam heating, and we have designed an Automatic Draught-regulator (shown in section in Fig. 519) by which this is perfectly secured." This apparatus will be more particularly described in the chapter on heating by steam.

Lack of space prevents detailed description of every kind of boiler, but probablv sufficient has been said to give the reader some idea of the principal types now in use. We must now pass to the consideration of another and most important part of a hot-water apparatus, namely, the radiator.

Radiators can generally be used either with low-pressure hot water or low-pressure steam; the subject will be best treated here, and need not be referred to in subsequent chapters.

The simplest form of radiating-surface consists of a straight length of pipe, which may be, of course, either wrought-iron or cast-iron. Where appearance is no object - as possibly in the basements of buildings and servants' bedrooms - cast-iron pipes are perfectly suitable, and the method of arranging them is shown in plan in Fig. 520. The pipes may be two, three, or four inches in diameter, and made with plain socketed joints, or with special joints as shown in Fig. 521. The latter is known as Richardson's expansion-joint, and possesses several distinct advantages. The joint is held together by bolts, and an india-rubber washer is put between the two ends of the pipe. If a length of pipe requires to be shortened, the socket end is cut off, and its place taken by a loose flange, held securely in position by a toothed gland, which grips the pipc and prevents slipping. This type of pipe is somewhat more expensive in first cost than the ordinary socketed variety, but the great facility with which joints can be made renders it little more expensive Q Q, Vessels containing mercurm- connection ty: I. steao boiler. W. water-connection to stand pipe; s. float: II, lever-arms; F, movable welght. v v,. valves for regulating the admiswhen fixed. Straight pipes require to be held either above the floor on small stools, which should be provided with rollers (to allow of expansion) of the form shown in Fig. 522, or they should be supported on wall-hracketa as shown in Fig. 523, or hung by slings from Wallbrackets as shown in Fig. 524. They may, however. be supported on simple brackets of T-iron, bent into the form of a hook, and let into the wall, as shown in Fig. 525, and this arrangement Lb quite sufficient where the lengths of pipe are not very considerable.

Fig. 519   Section of Korting's Automatic Draught  regulator

Fig. 519 - Section of Korting's Automatic Draught- regulator.

Fig. 520   plan of Hot water Pipe

Fig. 520 - plan of Hot-water Pipe.

Fig 621.   Section of Richardson'si India rubber Expansion Joint

Fig 621. - Section of Richardson'si India rubber Expansion-Joint.

Fig. 522  Front and End Ele vation and plan at Boiler Stool for Plpes.

Fig. 522- Front and End Ele-vation and plan at Boiler Stool for Plpes.

Fig. 523.  Elevation and Plan of Roller Bracket for Pipes

Fig. 523.- Elevation and Plan of Roller Bracket for Pipes.

Fig 524. Elevation and Plan of Bracket and Sling for Pipes.

Fig 524.-Elevation and Plan of Bracket and Sling for Pipes.

Fig 524.   Elevation and Plan of T iron Bracket for Plpes.

Fig 524. - Elevation and Plan of T-iron Bracket for Plpes.