a. Cross rail on which a guide is fixed to confine the air-pump rod in a vertical position.

b. The condenser.

c. The cold water cisterns, connected by a pipe d.

e. Eduction pipe, or passage for the steam from the cylinder to the condenser.

f. Injection cock, to admit the cold water into the condenser.

g. Foot valve, at the bottom of the air-pump, and communicating from thence to the condenser. h. Hand gear, for, stopping or starting the engine.

i. A rod, connecting the hand gear with an excentrick, fixed on the crank-shaft; the action of which communicates a vibratory motion to the rod i.

1. Connecting-rod, and double-ended lever m, fixed at the extreme end of a spindle, while a beviled wheel is attached to the other; the latter of which works the spindle of the steam-cone n.

o. The steam-cone, or cock, for admitting the steam from the boiler to the cylinder; beyond which is a contrivance for shutting off the steam, at the half, or any other part of the stroke, by which a very considerable saving in the steam, and consequently in the fuel, is effected.

It will very readily be seen, that the cone employed in this engine, for regulating the passage of the steam from the boiler to the cylinder, differs

very materially from the valves in Messrs. Murray and Wood's engine, and a slight examination of the sectional view in Plate V. will shew that the greater degree of friction that must of necessity attend the former contrivance, is more than compensated by its superior tightness and simpli city.

A. represents an end view of the cylinder and

steam-cone.

B. Side view of ditto.

C. Plan of ditto, taken at the horizontal line D. E. Steam-pipe.

F. Pipe, communicating with the condenser. G. Steam-cone, ground into its seat, and connected with the grease-cup H, by the means of which a regular supply of oil is furnished.

I. Plan of the steam-cone and passages, by which a communication is alternately opened between the steam-pipe and the upper end of the cylinder, and the condenser and the lower end of the cylinder, and vice versa.

When we consider the reciprocating steam engine in its present most improved state, both with respect to the admirable expedients for adapting it to the end proposed, and the skill displayed in the workmanship, we may almost venture to conclude that it has reached its utmost degree of per. fection; and yet it must be acknowledged, that it absorbs nearly half the power of the steam employed in friction, and in alternating its movements. This fact will be apparent by cal

culating what pressure on the piston of a reciprocating condensing engine, would be required to produce its nominal power; and it will be generally found, that (with the common speed) this will be obtained by accounting only from six to seven pounds pressure, per square inch, on the piston of small power engines; seven to eight pounds as to engines of from ten to thirty-horse powers; and from eight to nine pounds as to engines of larger powers, though the actual pressure on the piston is nearly sixteen pounds.

We have seen, that steam engines were, in the first instance, used for raising water, for which purpose the alternating motion of the beam is well adapted; at present, however, by far the greater number of reciprocating steam engines are required to impart a rotatory motion to the machinery attached to them.

The loss of power, to which we have already alluded, together with the expense of the construction of the reciprocating engine, have induced numerous attempts to invent an engine imparting a rotatory motion in the first instance; and the recent application of this prime mover to the purposes of navigation, has also acted as an additional stimulus to the attainment of so desirable an object, the inconveniences of a reciprocating engine being most sensibly felt in steam-vessels. Hitherto, however, those attempts have been attended with only partial success; for though many patent inventions have come under our observation, the

principal of which will be found in the Appendix attached to this work, they have altogether failed in attaining any decided superiority over the reciprocating engine, either from excessive friction, or the expense and nicety of workmanship required both in their construction and repairs.

Those difficulties appear to be obviated in Messrs. Masterman's Rotatory Engine, in a much greater degree than in any other that has come to our knowledge: the entire friction of one of those engines (without a condenser) having been proved, from actual experiment, not to exceed half a pound per square inch on the valves; the expense of construction being very considerably less than that of reciprocating engines, particularly in the larger powers, and the extraordinary simplicity of its parts securing it from almost any expense for repairs.

For steam navigation it appears admirably adapted, and when used with mercury instead of water, combines, in an eminent degree, economy of space and fuel; and this, in the latter case, it 'will be evident must be very considerable, on account of the almost total absence of friction.

Plate VII. Fig. 1. is a vertical and central section of the revolving part of the engine, called the troke, which is composed of a centre a, called the nucleus, of six hollow arms b, 1 to 6, called radii, and of a hollow ring cc, called the annulus.

Fig. 3. represents the nucleus; one end m is a perfect circular plane, called the face; six holes

of similar figure and dimensions are sunk in the face at equal distances from each other, following a direction parallel with the axis e, until half way through the nucleus, then, assuming a direction at right angles with the axis, they open in the periphery of the nucleus.

The axis passes through the centre of the nucleus at right angles to the plane of the face. The annulus consists of six equal parts, in each of which is fixed a steam-tight valve, exactly similar, and opening in the same direction by a hinge placed in the side of the annulus nearest the axis.

The rods which form the hinges of the valves, project through stuffing-boxes in the side of the annulus; and on each of these projections is placed a lever, at such an angle with the valve as to point to the axis when the valve is half open; and at the extremity of each lever is a weight d, more than sufficient to counterpoise the weight of the valve against which it acts. In the side of the annulus nearest the axis, are six holes at equal distances from each other; these holes are connected with the holes opening in the periphery of the nucleus by means of the hollow radii b, 1 to 6, thus forming a steam-tight communication between each hole in the face and the inside of the annulus.

Fig. 4. is a section of a metal plate or mask, which is of equal diameter with the face, having one side ground perfectly flat.

Through the centre of the mask is a circular