A "jack-head" pump, _N_, is driven by a small beam deriving its motion from the plug-rod at _g_, raises the water required for condensing the steam, and keeps the cistern, _O_, supplied. This "jack-head cistern" is sufficiently elevated to give the water entering the cylinder the velocity requisite to secure prompt condensation. A waste-pipe carries away any surplus water. The injection-water is led from the cistern by the pipe, _P P_, which is two or three inches in diameter, and the flow of water is regulated by the injection-cock, _r_. The cap at the end, _d_, is pierced with several holes, and the stream thus divided rises in jets when admitted, and, striking the lower side of the piston, the spray thus produced very rapidly condenses the steam, and produces a vacuum beneath the piston. The valve, _e_, on the upper end of the injection-pipe, is a check-valve, to prevent leakage into the engine when the latter is not in operation. The little pipe, _f_, supplies water to the upper side of the piston, and, keeping it flooded, prevents the entrance of air when the packing is not perfectly tight. The "working-plug," or plug-rod, _Q_, is a piece of timber slit vertically, and carrying pins which engage the handles of the valves, opening and closing them at the proper times. The steam-cock, or regulator, has a handle, _h_, by which it is moved. The iron rod, _i i_, or spanner, gives motion to the handle, _h_. The vibrating lever, _k l_, called the _Y_, or the "tumbling-bob," moves on the pins, _m n_, and is worked by the levers, _o p_, which in turn are moved by the plug-tree. When _o_ is depressed, the loaded end, _k_, is given the position seen in the sketch, and the leg _l_ of the _Y_ strikes the spanner, _i i_, and, opening the steam-valve, the piston at once rises as steam enters the cylinder, until another pin on the plug-rod raises the piece, _P_, and closes the regulator again. The lever, _q r_, connects with the injection-cock, and is moved, when, as the piston rises, the end, _q_, is struck by a pin on the plug-rod, and the cock is opened and a vacuum produced. The cock is closed on the descent of the plug-tree with the piston. An eduction-pipe, _R_, fitted with a clock, conveys away the water in the cylinder at the end of each down-stroke; the water thus removed is collected in the hot-well, _S_, and is used as feed-water for the boiler, to which it is conveyed by the pipe _T_. At each down-stroke, while the water passes out through _R_, the air which may have collected in the cylinder is driven out through the "snifting-valve," _s_. The steam-cylinder is supported on strong beams, _t t_; it has around its upper edge a guard, _v_, of lead, which prevents the overflow of the water on the top of the piston. The excess of this water flows away to the hot-well through the pipe _W_.