Method of Working.—­Turn the wheel so as to permit a small quantity of water to flow to the instrument.  Open the steam cock connecting the apparatus with the boiler.  Turn slightly the handle, which will admit a small quantity of steam to the apparatus; a partial vacuum is thus produced, causing the water to enter through the supply pipe.  As soon as this happens, which can be observed at the overflow pipe, the supply of steam or water may be increased as required, up to the capacity of the instrument, regulating either by means of the wheel and handle, so as to prevent any overflow.  The quantity of water delivered into the boiler, may be varied by means of the stop cocks on the steam and water pipes, without altering the handles on the injector; a graduated cock on the water supply pipe is very convenient for this purpose.

The machines are manufactured by Wm. Sellers & Co.  Philadelphia.

As an example of Portable Steam Engines, of which there are large numbers in this country of different manufacturers, we give the representation (fig. 67) of one made by J.C.  Hoadley, of Lawrence, Mass.

[Illustration:  Fig. 67.]

In these machines, the rules and proportions of the locomotive engine are adapted to the requirements of stationary power, for all purposes under forty horse power.  The leading ideas are:  high velocity, high pressure, good valve motion, large fire-box, numerous and short flues, and steam blast.  The characteristic features are:  great strength of boiler, fully adequate to bear with safety 200. lbs. pressure per sq. in., great compactness and simplicity, large and adjustable wearing surfaces, and the entire absence of all finish, or polish, for mere show.

The cylinder is placed over the centre of the boiler, at the fire-box end, so that the strain due to the engine is central to the boiler (which serves as bed plate); the starting valve is under the hand of the engineer when at the fire door; and both ends of the crank shaft are available for driving pulleys.

For the sake of compactness, the cylinders are set low, by means of a depression in the boiler between the stands of the crank shaft, to admit of the play of the crank and connecting rod.  All the parts are attached to the boiler, which is made of sufficient strength to bear all extra strain due to the working of the engine.

They have feed water heater, force pumps, Jackson’s governor and valve, belt for governor, belt pulley, turned on the face, steam gauge; everything, in short, necessary to the convenient working of a steam engine.  All engines are fired up and tried before they leave the shop, and they are warranted tight, safe, and complete.

A strong and convenient running gear, so arranged as to be easily attached and detached at pleasure, is furnished, if desired; forming, when separate, a useful wagon.

[Illustration:  Fig. 68.]