Fire Engine

Fire Engine, a machine designed to extinguish conflagrations. It pumps a continuous jet of water upon the fire by means of a force-pump worked by hand or steam. The principle being so simple, the history of the fire-engine extends far back in the past. Hero of Alexandria, writing about 150 B.C., describes a double-action pumping engine that is but slightly different from the manual of the present day. The sketch shows the general arrangement of a simple manual. A long lever hit is worked up and down about an axis through its centre, and gives an alternating motion to the pistons in the pumping cylinders cc. Water is supplied to these cylinders through the supply pipe shown in section at s, and, by means of the usual force-pump arrangement of valves, is drawn up through s and pumped into the central air chamber a. [Pump.] This is so called because it contains a quantity of compressed air that prevents the entire filling of the vessel. The delivery pipe passes from this air-chamber, and is supplied with the high-pressure water which the chamber receives. And though the water is pumped into the chamber discontinuously, by reason of the air cushion it emerges therefrom in a continuous stream and at a sufficient pressure to throw itself up to a considerable height. The supply pipe is stiffened with wire, and does not need to be very flexible; the delivery pipe or hose is made of canvas lined with indiarubber. Fireengines worked by steam are merely steam force pumps, provided like the above manual with the air-chamber to act as an accumulator. They are more powerful, and when well in action more effective. But their extra weight and mechanism involve more time in getting them to work, and the smaller manuals are often preferable. The latter may be set going almost immediately they arrive, whereas good steam fire-engines require from 5 to 15 minutes to get up steam.