The various styles of engine are all vertical in their action, and in all the pumps and steam cylinders are firmly and directly fastened to the boiler, the steam cylinders being attached directly to the steam dome.  This arrangement obviates the necessity of carrying steam to the cylinders through pipes of considerable length, and the machine has very little vibratory motion when in operation—­so little that it is not necessary to block its wheels to keep it in its place, or to take the weight off the springs before commencing work.

The pumps are placed on the engines as near the ground as they can be with safety, and are arranged so as to attach the suction and leading hose to either or both sides of the machine, as may be most convenient or desirable, so that less difficulty will be found in placing an engine for work, and when required to draw its own water, it has only to draw it the shortest possible distance.

Each engine has two “feed pumps” for supplying the boiler, and also a connection between the main forcing pumps and the boiler, so that it can be supplied from that source if desirable.  The tank which carries the water for supplying the boiler is so placed that the water in it is always above the “feed pumps,” an advantage that insures the almost certain working of these pumps.  These pumps are of brass, the best locomotive pattern, and one of them running with the engine, when at work, furnishes an ample supply of water to the boiler.

[Illustration:  Fig. 75.]

The engines are exceedingly portable; they can be turned about or placed for service in as contracted a space as any hand engine, and two good horses will draw a first-class engine with the greatest ease, carrying at the same time water for the boiler, a supply of fuel sufficient to run the engine two hours, the driver, the engineer, and the fireman.

Fig. 75 is a representation of the class of steam fire engine built by Silsbee, Mynderse & Co., Seneca Falls, N. Y. under Holly’s patent.

The boiler is vertical, with vertical water tubes passing directly through the fire.  These tubes are closed at the bottom and open at the top, where they pass through a water-tight plate, and communicate with the water in the boiler.  The arrangement of the tubes causes a constant current, the water rising on the outside of the tubes as they are heated, and its place being supplied by a current flowing downward through the tube to the boiler.  The smoke and flame pass among the tubes up through flues.

Both engine and pump are rotary, and of the same type.  They consist essentially of two elliptical rotary pistons, cogged and working into one another in an air-tight case.  The pistons fit close to the inside of the case, and gear into each on the line of their conjugate diameters.  The action is somewhat similar to the old-fashioned rotary pump, consisting of two cog wheels in gear with, each other, the spaces at