There are many cases where pipes of this character would be an eyesore if carried above the floor, but there is a system of placing the pipes in a specially-formed trench covered with a metal grating. There are great objections to this system, as the trench forms a most convenient receptacle for dirt and dust and the sweepings of the floors, and, while harbouring vermin, may be the source of infection. This system is shown in the right-hand part of the ground-floor in Fig. 526.

If the pipes are carried round the rooms in a channel formed behind the skirting-board, and protected by a metal grating, there is not so great an objection; this method is shown in the left-hand part of the ground-floor in Fig. 526 and also in 527. The channel above the floor, however, entails certain difficulties, as the pipes cannot well be carried below the doors, as in that case a dip would be formed, which might interfere with the circulation. In order to avoid the difficulties specified, it is found usually more convenient to place the main pipes between the floor of the room to be heated and the ceiling of the room below. These pipes are preferably carried in a special trench covered with a screwed board, so that access may be obtained to them. If the pipes are thus carried below the floor, it is merely necessary to bring from the main loop short branches to form the inlet and outlet of any particular radiator.

It is preferable to clothe the whole of the pipes where they are not needed for radiating heat, with some non-conducting material, such as slag wool, asbestos, magnesia, etc.

Formerly a very common type of radiator consisted of two vertical "ends", connected together by a number of horizontal tubes. These coils were usually set close against the wall, but in certain cases were fixed in the middle of entrance-halls, landings, and places of that nature.

These coils have now been practically superseded by a type having vertical loops, fastened together in groups of convenient size. The loops are made of different sizes, double, treble, quadruple, Ac., and of different lengths. The end loops are usually provided with feet, and the several parts are shown in Fig. 528, which represents a type of radiator known as the Safford; it is manufactured in Canada. A similar radiator is made by Mr. Keith, who has previously been alluded to. In this, each intermediate loop is an exact duplicate of the other, one side of each boss being tapped with a right-hand thread, and the other with a left-hand thread. The loops are then connected together by means of left and right nipples. In some cases the faces of the bosses are carefully machined, so that no packing other than red-lead cement is needed in order to make a tight joint, and in others a washer of paper soaked in boiled oil is employed.

Fig. 526   Diagrammatic View of Low preasure Hot water Pipes E, radiator, vp. vent pipe.

Fig. 526 - Diagrammatic View of Low-preasure Hot-water Pipes E, radiator, vp. vent-pipe.

Fg 527. Plpes in Channel formed in Wall.

Fg 527.-Plpes in Channel formed in Wall.

There are some radiators which are held together by long bolts. In my opinion these are distinctly inferior to the kind just described, as the l)olts expand and contract, and allow of leakage.

The Coil Radiator, re presented in Fig. 529, is made by Messrs. W. G. Cannon & Sons, and has been specially designed to afford a large heating-surface in small compass. There is a main bottom pipe, and connected to this are spiral coils of copper. Each coil is free to expand vertically without reference to any other coil, and although such a radiator is more expensive than the ordinary cast-iron type, it is very efficient in working. The coil is shown with a connecting tube at the top, as well as at the bottom, and the whole is proteeted by a wire guard, to prevent children from burning their fingers. The same type is also made inclosed in a cast-iron case with a door for access, and hit-and-miss gratings on the top and in front, as shown in Fig. 530. There is also a hit-and-miss grating behind, affording access for the external air. which passes out through the upper grating into the room.

Fig. 528. Staction and View of parts of the  Safford  Radiator for Hot Water.

Fig. 528.-Staction and View of parts of the "Safford" Radiator for Hot Water.

F1g 529. Coil Radiator, with Wire Guard.

F1g 529.-Coil Radiator, with Wire Guard.

I have already drawn attention to the desirability of warming the incoming air which is used for heating and ventilation, and the present is a fitting opportunity for pointing out several methods by which this result may be obtained. As shown in Fig. 530, a special air-inlet must first be provide-1 in the external wall, and the inside of this opening should be carefully rendered with Keene's or other hard cement. The exterior face of the opening should be protected with a cast-iron grid, which is so fixed in its frame as to be capable of easy removal, when the inside of the opening is to be cleaned. The inner fa<e of the inlet should be provided with a suitable hit-and-miss grating, and the inlet itself should be as near the floor-level as possible; this hit-and-miss grating must be capable of adjustment by means of a handle, which comes to the outside of the case either at the side or at the top. The case itself, which is usually of cast-iron, may be made as ornamental as may be desired, but it should have a hit-and-miss grating of ample size on the top, and also at the front close to the floor. The action of the radiator and case is as follows. In mild weather the inlet-grating is opened to its full extent, the front grating in the case closed, and that in the top of the case opened wide. The heat of the radiator causes an upward current of air through the upper grating, and the external air passes in to take its place. The warmed air passing into the room will have a temperature dependent upon the temperature of the radiator, and upon the velocity of the air passing through the external wall. If now it be found that the volume of air entering the apartment is too large, the grating at the inlet may be entirely elosed, and the grating in the front of the case opened. Air from the floor level of the room will then be drawn into the case, and will pass upwards among the coils of the radiator, and out into the room through the top grating.

Fig. 530   Sectlon showlng Coil Radiator in cast iron case, with Air Inlet, etc.

Fig. 530 - Sectlon showlng Coil Radiator in cast-iron case, with Air Inlet, etc.