axis at f. The upper part of the spindle is furnished with a socket h, which is allowed to ascend when the centrifugal force of the governor increases. Should, however, its motion decrease, the balls jj will descend, while the socket h will ascend, and with it the lever l.

c. A rod connecting the levers 7 and b, which by their joint action communicate the motion of the governor to the throttle-valve a, so that when the engine is at rest the balls jj will also be resting against the arms kk, the upper end of the levers ee will be brought nearer to each other, and the rod c being raised, the throttle-valve will be turned in a horizontal direction, thus allowing a large portion of steam to pass through the pipe C.

DD. A pipe connecting the top and bottom of the cylinder with the throttle-valve a. steam-pipe c E. The eduction-pipe, passing down to the condenser.

The valves no have each a cylindrical tube or spindle passing through the stuffing-boxes r and s, to the upper end of which are screwed two other stuffing-boxes t and u, so that both valves are allowed to slide up or down without permitting the steam to pass.

p. q. Two other valves similar to n o, whose spindles pass through the stuffing-boxes tu.

Fig. 2. Is a front view of the two sliding bars which are intended to give motion to the valves

nopq. These bars are kept in a perpendicular direction by the pieces, and the guide 1. In the lower ends of the bars are two friction rollers 3 3, which are acted upon by the two eccentric wheels 4 4, and raised and depressed alternately by the upward and downward stroke of the engine.

The horizontal shaft Z derives its motion from a similar shaft Y placed at right angles, communicating by means of beveled wheels with the crankshaft.

9, 10, 11, and 12, are four arms, fixed to thebars v v, and w w, for the purpose of moving the valves.

13. A lever or handle revolving upon a stud screwed in the pipe E, which, by its action, is made to open and shut the steam-valves when the engine is first set to work.

18. A mercurial or barometer gauge for measuring the pressure of the steam above or below that of the atmosphere. One end of the barometer-gauge enters the steam-pipe DD, while the other is open to the atmosphere and furnished with a gauge.

The communication between the barometergauge and steam-pipe may be closed at pleasure by the stop-cock 19. In the lower or bent part of the tube is placed a quantity of mercury, and it will be evident that upon opening the cock 19, the pressure of the steam endeavouring to

pass by the pipe DD, will be counterbalanced by the pressure of the atmosphere. Should, however, the elasticity of the steam exceed that of the atmosphere, the mercury. will be raised in the outer leg of the gauge, and the difference in the altitude of the two columns will show the working power of the steam. When the altitude of the column 18 exceeds that of 19 two inches, the pressure of the steam will exceed that of the atmosphere nearly one pound per square inch.

A nearly similar instrument is also employed to ascertain the degree of rarefaction in the condenser. It consists of a bent iron tube 21, the lower end of which opens to the condenser. The mercury is poured into the tube at the open end 23, and the stop-cock 22 being opened, the mercurial column at 23 will be depressed, while that on the opposite side will be raised in a proportionate degree. This effect is produced by the vacuum formed in the condenser. If the condenser and air-pump are in good order, the mercury will descend about fourteen or fifteen inches, which will indicate a pressure of so many pounds upon the square inch. So that if we refer to the two gauges, it will be found that the total amount of power, or acting force upon the piston, will be represented by the difference in the altitude of the two mercurial columns added together.

To put the engine in action, the fly-wheel W, Plate IV. must be turned till the crank T is in

a horizontal direction, when the piston will be in the middle of the cylinder B, and the eccentric wheel 4 on the upper side of the shaft Z. The bar ww, will also be raised, together with the valves o and p, and the handle 13 being turned, a passage will be opened for the steam to blow from the pipe C, and thus expel the atmospheric air, which previously filled the different parts of the engine. When this is effected, and the temperature of the engine raised, the lever 13 must be turned to its original situation; the bar vv, together with its valves, will descend, and the steam will be shut off from the upper side of the cylinder; while, at the same time, the passage will be stopped between the under side of the piston and the condenser. The injection-cock must now be opened, which will admit a small jet of cold water into the condenser, and a vacuum will be formed above the piston, while the steam is entering beneath with a pressure equal to or greater than that of the atmosphere.

The piston-rod being thus made to ascend in the cylinder, the opposite end of the beam Q will be depressed in a proportionate degree, and the rod S, as well as the crank T, will also descend, and a rotatory motion be produced. The fly. wheel will also have acquired a sufficient degree of momentum to carry the crank past the perpendicular, and the piston will have arrived at the top of the cylinder; the situation of the valves

being reversed by the action of the excentric wheels, and a continuous motion is thus produced.

The High-pressure Engine, in its most simple form, may easily be described by reference to the following diagram.

E

The cylinder A is furnished with a piston and rod B, the latter being made to fit air-tight in a stuffing-box at the top of the cylinder. A fourway cock C is also provided for the admission of highly elastic vapour, and its subsequent discharge into the atmosphere. The action of the four-way cock will be best understood by the section D; in which E represents the waste-pipe connected with the chimney, while two other apertures serve to convey the steam alternately to the upper and under side of the piston, and a third

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