"But," it may be asked, "why is a fire not always kept burning, and steam constantly at high pressure?" The answer is that a constant fire, whether of coal or of oil, would cause soot or smoke to accumulate; while the Bunsen gas-burner affords as clear a heat as any, and maintains the water at a great heat, or even at boiling-point. Near the funnel, but not so high, rises a large, gleaming metal cylinder, closed and dome-shaped. This is the indispensable air-chamber, without which even the powerful force-pumps could not yield so steady and persistent a stream. A small air-chamber is now added to the suction-pipe by which the water is drawn to the engine. The use of the air-chamber in connection with this pipe greatly steadies the engine, the vibration caused by the throbbing of the powerful machinery as it draws and forces along such a quantity of water being very great. The nozzle of the hose belonging to one of the largest steam fire-engines measures 1¼ inch in diameter, some nozzles being as small as ¾ inch; and a large column of water is being constantly driven along the hose at a pressure of a hundred and ten pounds to the square inch, and forced through the narrow nozzle; here it spurts out, in a large and powerful stream, to a distance of over a hundred feet. It is obvious, therefore, that the power exerted by the steam-driven force-pumps and air-chamber is very high; and although such an engine may be in some folks' opinion only a force-pump, it is a force-pump of a very elaborate character; and not inexpensive, the average price being about £1,000. Every steam fire-engine carries with it five hundred feet of hose. The hose is made in lengths of a hundred feet, costing about £7 a piece, without the connections. If you examine a length, you will find it made of stout canvas, and lined with india-rubber, the result being that, while it is very strong, it is yet very light. Miles of it are used in the service; and upstairs in the hose-room you will find a large stock kept in reserve. Every piece is tested before being accepted. [Illustration: POWERFUL STEAM FIRE-ENGINE FOR THE METROPOLITAN FIRE-BRIGADE. _Capacity, 350-400 gallons per minute. Delivered to the brigade, February 9th, 1899, by Messrs. Shand, Mason, & Co._] Water is forced through it by hydraulic power at a pressure of three hundred pounds to the square inch, so that when at work, with water rushing through at a hundred and ten pounds' pressure, it is not likely to split and spill the liquid on the ground. The splitting of hose in the face of a fierce fire would be a great calamity. When charged with water, its weight is very heavy; and to enable it to be carried more easily, a loop called a "becket" is attached at distances of about ten feet. The greatest care is taken of the hose. When it is brought back, drenched and dripping, from a fire, it is cleaned and scrubbed, and then suspended in the hose-well to dry.