The main parts of the steam fire-engine are the boiler, engine, pumps, and the vehicle on which these are mounted. Boilers are generally of the vertical water-tube type. The engines and pumps are also generally vertical, double-acting, and in duplicate. A few makes have both rotary steam and water cylinders. instead of the more common steam-pistons and water-plungers or reciprocat ing engines. Some light machines have hori zontal engines and pumps. To facilitate the preparation of fire-engines for service, heaters are maintained in the engine-house to give a constant supply of hot water to the engines. When the alarm strikes the fire is kindled be neath the boiler, and steam is soon available. The rated capacity of steam fire-engines ranges from about 1300 to 400 gallons per minute, and their weights from 9500 to 5000 pounds. The self-propelled engines already mentioned, as now built, have a capacity of 1350 gallons per minute, and weigh 17,000 pounds when equipped for ser vice. They are 10 feet high, 163/4 feet long. and feet wide. The engine is propelled on the road by power from the main crank-shaft, through two chains running over sprocket wheels on the main rear wheels of the engine. The driver steers the engine by means of a hand wheel and rod connected with the front axle through a bevel and worm gearing. By the removal of a key the road-driving mechanism may be discon nected, whereupon the power becomes available for the pumps. One of these engines, made for the city of Hartford, Conn., when on its first trial is reported to have thrown a stream through 50 feet of 33/4-ineh hose to a horizontal distance of 348 feet with a 13/4-inch nozzle, and 3193/4 feet with a 2-inch nozzle. The first, and for many years probably the only thorough test of steam fire-engines, was that made in 1876 at the Centennial Exhibition at Philadelphia. The results are given in detail in the official report of the exhibition, together with descriptions of the several engines. A inure recent series of tests was made at Boston in 1893; both the conditions and the results obtained are given in detail in the report of the city engineer of Boston for 1893.94. The engines tested were those in regu lar service by the fire department, sonic practical ly new and others fifteen years old. In all cases the engines drew water from a hydrant under pressures of from 30 to 40 pounds. The largest average quantity of water pumped per minute during the whole of one test was 910 gallons, by a Clapp & Jones engine, the pumps having been run two hours and twenty-three minutes and throwing a total of 130.121 gallons of Ntater. The average steam-pressure was 101,3 pounds, and the average waier-pressure at the pumps was 112.8 pounds. For shorter periods during this test hotter results were obtained; thus, for about twelve minutes there was a discharge of 1022 gallons per minute. It must be understood that various combinations of hose, both as to length and the number of lines, and nozzles of different sizes, were used; but even with three lines of hose, each 500 feet long, two of which were 23/4 inches in diameter and had nozzles, while one was 3 inches in diameter and had a nozzle, an average discharge of 900 gallons per minute was maintained for sixty-four minutes, with water-pressure of 53.5 pounds at the nozzles. As stated, the pumps ran two hours and twenty-three minutes altogether, but the engine was under steam for three hours and eight minutes, during which time 2869 pounds of coal were burned and 8398 pounds of water evaporated. This was 2.93 pounds of water per pound of coal, or 3.51 pounds from and at 212° F. The coal used per square foot of grate per hour was 172.1 pounds, and the duty in foot pounds was 7,758,300 per 100 pounds of coal i.e. for every 100 pounds of coal burned 7.758,300 pounds of water was raised to an equivalent of 1 foot in height. This engine weighed 7970
pounds. had steam-cylinders 9 inches in diameter, water-cylinders 53/4 inches in diameter, both of 8-inch stroke. its boiler was inches in diameter, with a heating surface of 140% square feet. The other engines in this Boston test were all smaller, having steam-cylinders from about G to 8J,4 inches in diameter, 4 to 5 inch water-cylinders. but with about the same length of stroke as the more powerful engine. Their calculated capacities ranged from about 500 to 700 gallons per minute, and their average work during the tests was the throwing of 499 to 596 gallons of water per minute. The duties of these engines ranged from 5,882,000 to 14,026,000 foot pounds per 100 pounds of coal, and the water evaporated from and at 212° F. ranged from 2.26 to 5.87 pounds per pound of coal. The range of duties was about 10 per cent. as great as that. of fair to high grade stationary pump ing engines; but it must be understood that fuel economy is a secondary matter in a fire-engine, the main object being to get the engine to the fire and throw the maximum of water in the minimum of time after the alarm. To enable the engines to be drawn by horses at a high rate of speed. lightness is essential. Fire-engines mounted on fire-boats, like those used by New York, Detroit, and other cities, may be designed with less regard for weight and with more con sideration for fuel economy; but here, also, quick ness and effectiveness of service ranks first, so the chief advantage of such fire-engines is that they may he made practically as capacious and powerful as is desired, and may approach fires closely from the water-front side, where the ordi nary steam tire-engine cannot be driven. The fire-boat Robert .t. Wyck, for the New York Fire Department, put in use in April, 1898, has two sets of pumps, which on test delivered about 3200 gallons of water per minute each, with pump pressures of about ISO pounds. The tire-boat Itelu ye, built in 1900 for the city of Detroit. was designed to have two sets of vertical, triple-expansion pumping engines, with 14-inch steam and 8-inch water cylinders, all of 11.inch stroke, and with a combined capacity of 6000 'gallons per minute. Two huge nozzles were in eluded. besides 20 connections for hose. Besides steam, gasoline engines are sometimes used for driving the pumps of portable engines, being designed particularly to replace the small hand-worked tire-engines used in villages.
Chemical fire-euyines and extinguisthers range all the way from apparatus mounted on wheels and propelled by horses or men to small tanks carried on a tireman's back, or small hand foree pumps. The aim of all such devices is to smother the lire by means of some gas, such as carbonic acid gas. The larger and more effective appara tus include a generating tank or tanks, in which water and soda are placed, with an agitator to aid in dissolving the soda, an acid-feeding cham ber, and the necessary hose. If the generating apparatus is in duplicate, with proper hose con nections, continuous streams may be thrown; otherwise the stream will cease while recharg ing is in progress. The water serves as a medium to carry the gas, and the gas is the motive force for the water. Small quantities of water are required, as compared with fire-engines, thus permitting a relatively light apparatus and small and easily managed hose. For incipient fires, or some of those where water is inetheient, the chemical apparatus is very useful, and it may be employed to advantage in some cases where the cost of steam fire-engines is prohibitive. It is considered advantageous to combine the chemical engine with an ordinary hose-wagon, and thus cope with small fires in an effective and satisfactory manner. See FIRE-EXTINCT:18'1ER. For further information on fire-engines, see FIRE