To avoid difficulty in making hose connections, these for suction and delivery are extended on each side of the extreme rear of the frames, where they are connected up out of the way of the engine driver.

The engines and pumps, situated at the front of the boiler, are a compact piece of work. They are of the vertical double-cylinder type, the cylinders being uppermost. These are of cast iron, and lagged, the slide-valves being situated in a central steam chest. The pumps are of gun-metal, cast with the crankshaft bearings, and connected to the cylinders with turned steel stays. They are double-acting, driven direct from the steam pistons, the rods having slotted crossheads to drive the crank. shaft from which the slide-valves are worked. A point to note in the pumps is the accessibility of the valves, which are exposed on the removal of a cover on the valve chest. The mere loosening of a nut removes a pair of valves, and a damaged valve can be replaced within from 3 to 4 minutes from the time of stopping to restarting the engines. The valves are of indiarubber, and the guards and gratings are secured with copper studs. A by-pass valve in the pump opens a communication between the suction and delivery passages, so that the engine may start against a head of water in the hose.

Messrs Merryweather have an oil-fired engine, the motor "Fire King" supplied to the London County Council and others. It will travel at speeds of from 25 to 30 miles an hour, can ascend gradients of 1 in 6, and its capacity is 500 gallons a minute, throwing a 1-in. jet to a height of 160 ft. The boiler is petroleum fired. Complexity of parts has been avoided by making the same cylinders and pistons furnish both the pumping and the motive power. As both operations are never required simultaneously this is very easily done through a countershaft which can be thrown in or out of gear. Steam can be raised to working pressure in from 6 to 8 minutes, from cold water, or in 60 seconds if a low pressure is kept up continuously by a gas burner or oil heater while the engine is in the station. The engine carries water and fuel for several hours' working, which includes either travelling on the road, or pumping when it has

reached its destination. The wheels are fitted with solid rubber tyres and non-skid chains.

Fig. 9, Plate I., illustrates this type of engine, which is similar to those supplied to London. It has the addition of a chemical engine for first aid, which is carried under the main box in front, and the reel for chemical hose is fitted above the box as illustrated.

The following very brief remarks have reference to the more salient points of the Shand, Mason fire engines:-Fig. 10, Plate I. As rapid steam raising is essential, the boiler claims first attention. This is a vertical type with inclined water-tubes, crossing the fire-box in each alternate row at right angles. The working pressure is 125 lb. to the square inch. The fire can be lighted and steam of 100 lb. pressure can be raised from cold water under ordinary circumstances in 8 to 10 minutes while travelling, without any stoking; but by the use of a new exhauster fan arrangement, the times mentioned are reduced to 5 and 6 minutes. Yorkshire iron is used in the boiler, with the longitudinal seams welded, and brass tubes.

The engines are of the double vertical type, adopted since 1889. They work directly on to double-acting vertical pumps, the two being rigidly connected. Two piston rods convey the movement of each piston to its pump rod. The crankshaft is driven by connecting rods of special type running from a joint in the head or cross piece of each pump rod. The eccentrics for working the slide-valves of the engines are situated at the ends of the crankshaft. The piston rods, and the rods for the slide-valves and pumps are of bronze, the pumps of gun-metal, and all surfaces with which the water comes in contact are of these alloys, or of copper, so that corrosion cannot occur when an engine has been idle for a considerable period. The moving parts are balanced to work steadily at high speeds.

By means of the oil-fuel apparatus, adopted since 1893, steam can be raised to 100 lb. in from 1 to 1 minute, when 20 or 30 lb. of steam is maintained, as in the London Fire Stations. One great advantage is that there are no sparks or flying cinders escaping from the chimney, another is that no preparation of the furnace is necessary when the engine re

turns to the station. Another improvement is the boiler heater-a miniature cross-tube boiler -by the use of which a low steam pressure may be automatically maintained while the engines are at the fire station. It may be regulated from boiling point merely, to 20 or 30 lb. pressure of steam. Variable steam expansion has been adopted since 1898, by varying the point of cut-off from three-fourths to one-half the stroke. The amount is read on an index plate at the back of the lever that operates the expansion gear. Besides the economy secured, fewer sparks escape from the chimney, due to the softness of the exhaust.

Side stoking is adopted in preference to stoking at the rear. The principal advantage claimed is that the engine driver and the firemen are not in one another's way at critical times when stoking, and the coupling up of hose has to be done with all speed. Another point in its favour is that the pumps can be arranged considerably lower, giving a decided advantage when pumping from a depth, the lowering of the centre of gravity also allowing the engine to travel better.

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Fire engines may often be employed for other duties than extinguishing fires; as for transferring water from one site to another, removing water from places where it is not wanted, for flushing sewers, and washing silt and mud from places where it has collected, for washing buildings, irrigating land, &c. Floating fire-pumps are also used on rivers for extinguishing fires.

Fire Flues.-Furnace Flues, as distinguished from smoke flues.

Fireproof Structures. An absolutely absolutely fireproof structure may be regarded as impossible if material that would burn is stored within it, or inflammable buildings are close to it. No building can sustain without damage the application of intense heat unequally applied, and sudden cooling by cold water. Even without the latter the effect of expansion by heat is almost necessarily disastrous.

When iron began to take the place of wood for the framework of floors and roofs it was supposed that as the materials were not inflammable the buildings could not be injured by fire. But experience has shown that the expansion

and bending of wrought members in a fire is more dangerous to the walls of a building than if such members were of wood. Cast iron seldom gets hot enough to bend, but it often cracks under the application of cold water in a fire. Stone cracks also when subjected to great heat.

The best fire-resisting materials are brick-work, including fire-brick, terra-cotta, &c., and concrete, and plaster. These are the materials that are used in all fire-resisting structures, but iron and steel are generally employed also, protected by the other materials, provision being made where possible for the greater expansion of the metal. Brick-work alone is used largely, and brick arches are preferred to joists or girders over openings in walls.

To prevent fires in one room or floor spreading to others it is also necessary to have means of closing all doorways, stairways, and windows, so that they shall be as impassable barriers to the fire as the walls and floors themselves. building, therefore, with open stairways or lifts, wood doors, and no protection to windows is not fire-resisting.

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Next to brick-work used alone, reinforced concrete is the best fire-resisting material for building. The metal embedded in the concrete is protected from the heat to a great extent, and the combination gives great strength with less bulk than would generally be required if brick-work alone was employed. In floors especially, brick arches would occupy too much depth. For exterior walls the appearance of concrete is not considered equal to bricks, nor is there quite so much advantage in employing it as in the case of floors. In floors, metal or wood joists are usually essential, and these can be more easily protected by concrete or plaster than by brick work. There are innumerable methods of constructing such floors.

Special attention has naturally been paid to the construction of fireproof floors, because formerly when they were of wood they invariably became burnt out, while the brick walls remained standing, or suffered injury only through the breakdown of the floors. As brickwork for floors is generally impossible, a combination of metal and concrete is the alternative, and the methods of arranging this combination are numerous. Where girders

or columns have to be protected, the concrete or plaster is usually not applied directly to them, but to metal lathing, or expanded metal attached to the surface, with a space between.

Firing. The art of firing consists in so regulating the relative supplies of air and fuel that the most perfect combustion possible under the crude practical conditions of the furnace shall take place. Good combustion cannot take place with heavy indiscriminate firing. At the moment of throwing fresh coal upon the fire, and for the few minutes immediately following, there is a rapid liberation of gases-carbon, hydrogen, and hydrocarbons. During these periods a large and immediate admission of air is necessary to burn them up, otherwise a considerable proportion of them will pass off unconsumed. With heavy firing and natural draught it is impossible to obtain the necessary quantity of air. Light firing with frequent charges is therefore economical. The fuel must be introduced in such quantities that no perceptible amount of coloured gases passes out of the chimney. The fuel must also be distributed judiciously over the incandescent mass beneath.

The proper way to fire in Lancashire and Cornish boilers furnished with a dead plate is to throw the fuel upon and a little way beyond the dead plate, and leave it there until coked. When coked it is thrust forward over the clear fire beyond, and fresh fuel thrown on the front of the fire. In locomotive boilers the fuel is flung into the four corners and allowed to coke, afterwards being drawn towards the central portions of the grate area. Firing thus, the gases come off slowly, and the oxygen in the air is allowed time to enter into combustion with them. With increase in draught the fire can be thicker, because a larger quantity of air passes through and over the grate in a given time. So that with forced draught it is necessary to keep a thicker fire and to fire more heavily in order to derive the fullest advantage from the increased quantity of air used. With a thin fire and forced draught the air tends to cool the fire, and there will not be sufficient fuel to combine with all the oxygen of the air.

In consequence of the very brief period available for the diffusion and intermingling of the atmospheric air with the gases on the hearth of

a boiler furnace, only amounting to the fractional part of a second, various methods have been devised to promote and favour the chemical reactions necessary to perfect combustion. This is the essential secret of good hand firing. It is provided for in the various systems of machine stoking, and in forced draught. Many have been the devices resorted to in order to introduce the air in those localities where it will best promote combustion. Speaking generally, the aim is not to permit the inrush of a body of cold air in mass, but to introduce it at various areas, more or less broken up into layers or jets, so that its union with the gases may be effected immediately and completely instead of partially. In various systems the gases have been introduced below the fire-bars, passing up through them in jets above the grate from the front end and over the fire-bridge.

To ensure the perfect combustion of the chemical elements liberated from the fuel, it is desirable to liberate air both above and below the fire-bars; in what proportions depends upon the thickness and condition of the fire at a given time. Air in passing up through the grate-bars becomes charged while in contact with the fuel with carbon, forming carbonic oxide. Unless this meets with a supply of oxygen above the fuel, sufficient to convert it into carbonic acid, it will pass off, causing a loss of heat, and if the chimney temperature is high enough, will burst into a blue flame on meeting with oxygen at the mouth. This will occur with a thin, clear fire in the absence of a proper supply of oxygen above the grate-bars.

Again, in the case of a thick fire in which air is introduced only from below, the probability is that the entire combustion will be imperfect. The carbon and hydrogen distilled from the coal in the process of coking require an ample supply of oxygen to produce steam, and the oxides of carbon. If this supply is not forthcoming, or if present, and the furnace temperature is fallen too low, much of the carbon will pass off unconsumed as black smoke, and a portion of the coal-gas will escape in the form of hydrocarbon, only igniting at the chimney top on meeting with the air.

The experiments of Mr Spence showed that neither with a thick nor a thin fire is it possible,