FIRE ENGINE

This most useful machine is constructed in a variety of forms, which all, however, agree in one principle. It generally consists of a double forcing pump communicating with the same air ve el; and instead of a force-pipe a flexible leathern hose is used, through which the water is driven by the pre ure of the condensed air in the air ve el. The annexed diagram represents a section of the apparatus. The pipe T descends into a receiver or ve el containing a supply of water. This pipe communicates with two suction valves V, which open into the pump barrels of two forcing pumps A, B, in which solid pistons P are placed. The piston rods of these are connected with a working beam F, elon|jj gated so that a number of persons may work at both ends of it at once. Force-pipes t, t, proceed from the sides of the pump barrel above the valves V, and they communicate with an air ve el M, by means of forcirFg valves V, which also open upwards. The pipe descends into the air ve el near the bottom. This pipe is connected with the flexible leathern hose L, the length of which is adapted to the purposes to which the machine is to be applied. The extremity of the hose may be carried in any direction, and may be introduced through the door's and windows of buildings. By the alternate action of the pistons, water is drawn through the suction valve, and propelled through the forcing valves, until the aiT in the top of the ve el M is highly compre ed. The pre ure acts on the surface of the water in the ve el, and forces it through the leathern hose in a continued stream, so as to spout from its extremity with a force depending partly on the degree of condensation, and partly 453 FIRE FLY. on the elevation of the extremity of the hose above thOv level of the engine. It is to be considered that the pre ure of the condensed air has, in the first instance, to support a column of water, the height of which is equal to the level of the end of the tube above the level of the water in the air ve el; and until the pre ure exceeds what is nece ary for this purpose, no water can spout from the end of the hose; and,.consequently, the force with which it will so spout will be proportional to the exce of the pre ure of the condensed air above the weight of the column of water, whose height is equal to the elevation of the end of the hose above the level of the water in the air ve el. {Cabinet Cyclopcedia, " Hydrostatics and Pneumatics," p. 326.) The fire engine has received various improvements from Bramah, Dickens on, Simpkin, Raven tree, Philips, and others. The above description applies to Newsham's engine. Bra i thwaite's steam fire engine is an application of the power of steam to the working of the fire engine. The mechanical arrangement consists of two cylinders of about six inches in diameter, one of them being the steam cylinder, and the other the water pump; and they are placed horizontally, so that a parallel motion is easily produced. This engine will deliver 9000 gallons of water an hour at the height of 90 feet. The time of getting the machine into action, from the time of igniting the fuel (the water being cold), is only 18 minutes. Some of the Fire Insurance Companies in London have floating engines on the Thames, which are extremely serviceable in cases of fire among the shii)ping or buildings near the river. [s. 466]