Page:Popular Science Monthly Volume 47.djvu/509

Rh engines have piston pumps; the Silsby engines have rotary pumps, and the La France Engine Company manufactures two distinct styles of engines—one with a piston pump and one with a rotary. The piston pump needs no description here, but it will be well to say a few words in regard to the rotary pump. The engine in this case is composed of two cams, which to the uninitiated are irregular cog-wheels with alternating large and small cogs, working in a steam-tight case. The steam entering from one direction forces these cams to revolve with great rapidity. The pump is composed of cams somewhat similar, which are connected with the engine cams, and when revolving suck the water and force it through the discharge pipe with great pressure. The capacities of steam fire engines differ from three hundred gallons per minute in the smallest sizes up to twelve and thirteen hundred gallons per minute in the largest.

Self-propellers are very little used at the present day. Boston, Providence, Hartford, New York, Brooklyn, Detroit, Chicago, Milwaukee, and other cities, have all tried them, but they have been very generally discarded for engines drawn by horses. Hartford is a notable exception to the list, there being two self-propellers in her department. The latest of these is an Amoskeag engine by the name of Jumbo, and has a capacity of thirteen hundred and fifty gallons per minute. This is probably the largest land fire engine in the world. The city departments are always furnished with the larger sizes of engines drawn by horses, but in many towns engines of lighter draft, that can be drawn by men, are often used. Crane-neck and straight frames are both used, but the former are more common. The American Fire Engine Company make a combination engine and hose wagon called the Columbian engine. The wagon part is forward, and the engine and boiler are over the rear wheels. This is very convenient in suburban departments, as it reduces the number of pieces of apparatus. The fire-engine makers of the United States supply the home market exclusively, and a number of machines have been sent to Canada and to foreign countries.

The most powerful allies of the land engines are fire boats, that are now used by all large cities bordering on the water. The capacity of a fire boat is often equal to that of ten to twenty land engines, and is limited only by the size of a boat that can be worked quickly and easily among the crowded shipping of a harbor. As has been seen, New York had a floating hand fire engine in use during the early part of this century, but it was not in service for any length of time. After steam vessels came into general use, harbor tugs were often provided with fire pumps, that they might aid in extinguishing fires on the water fronts. The first boat built expressly for fighting fire was launched in 1872,