frame are firmly fixed. G represents a cock for conducting the steam, as may be more clearly seen by observing fig. 2, which is a plan of the top of the cylinder. b, Figs. 1 and 2, represent the passage from the boiler to the cock, G; this pasage has a throttle valve, or shut, adjustable by a handle, so as to wiredraw the steam, and suffer the supply to be quicker or slower. The position of the cock is such, that the communication from the boiler, through b, by a channel in the cock, is made good to d, which denotes the upper space of the cylinder above the piston, at the same time that the steam pipe, a, (more fully represented in Fig. 1.) is made to afford a passage from the lower space in the cylinder beneath the piston to the channel, C, through which the steam may escape into the outer air, or be directed or applied to heating fluids, or other useful purposes. It will be obvious that, if the cock be turned one quarter of a turn in either direction, it will make a communication from the boiler passage, b, to the lower part of the cylinder, by or through a, at the same time that the passage r, from the upper part of the cylinder, will communicate with C, the passage for conveying off the steam. PQ is a piston rod moving between guides, and driving the crank, R S, by means of the rod, QR, the axis of which crank carries the fly, T, and is the first mover to be applied to drive the machinery at S. X Y is a double snail, which in its rotation presses down the small wheel O, and raises the weight, N, by a motion in the joint, M, of the lever, O N, from which downwards proceeds an arm, M L, and consequently the extremity, L, is at the same time urged outwards. This action draws the horizontal bar, L I, and carries the lever handle, H I, which moves upon the axis of the cock, G, through one-fourth of a cir cle. It must be understood that H I is fore-shortened, (the extremity, I, being more remote from the observer than the extremity, H,) and also there is a clack or ratchet wheel on the part, H, which gathers up during the time that Lis passing outwards, and does not then move the cock, G, but that, when the part X, of the snail opposite O, that is to say, when the piston is about the top of its stroke, then the wheel, O, suddenly falls into the concavity of the snail; and the extremity of L, by its return, at once pushes I H through the quarter circle, carries with it the cock, G, and turns the steam upon the top of the piston, and also affords a passage for the steam to escape from beneath the piston. Every stroke, whether up or down, produces this effect by the half turn of the snail, and reverses the steam ways, as before described; or the cock may be turned by various well-known methods, such as the plug with pins or clamps striking on a lever in the usual way, and the effect will be the same, whether the quarter turns be made backward or forward, or by a direct circular motion, as is produced by the machinery here represented; but the wear of the cock will be more uniform and regular, if the turns be all made in the same way.' The same specification likewise describes a very simple and ingenious method of giving motion to the fly wheel, by making the piston rod of an inflexible bar, and connecting it at once with the crank. The cylinder and boiler are allowed to vibrate on pivots, and thereby follow the revolving of the crank. The drawing here given represents also the outline of a machine for rolling sugar canes, thereby showing at once the connexion of the engine with the machinery of the mill. "In the subjoined diagram, the working cylinder, C, with its piston, steam pipe, nozzle and cock, are inserted in the boiler, as here delineated. The piston rod drives the fly, upon the arbor of which is fixed a small wheel which drives a great wheel upon the axis; the guides are rendered unnecessary in this application of the steam engine, because the piston rod is capable, by a horizontal vibratory motion of the whole engine upon its pivots, O, to adapt itself to all the required positions; and while the lower portions of the chimney partake of this vibratory motion, the upper tube, E F, is enabled to follow it by its play upon the two centres or pivots in the ring above. In such cases, or constructions, as may render it more desirable to fix the boiler with its chimney and other apparatus, and to place the cylinder out of the boiler, the cylinder itself may be suspended for the same purpose upon trunnions or pivots in the same manner, and one or both may be perforated, so as to admit the introduction and escape of the steam, or its condensation. And in such cases, where it may be found necessary to allow of no vibratory motion of the boiler or cylinder, the same may be fixed, and guides be used. The manner in which the cock is turned. is not represented in the two drawings, but every competent workinan will, without difficulty, understand how the stroke of pins duly placed in the circumference of the fly, and made to act upon a cross fixed on the axis of the cock, or otherwise, will produce the motion. The steam which escapes in this engine is made to circulate in the case round the boiler, where it prevents the external atmosphere from affecting the temperature of the included water, and affords by its partial condensation a supply for the boiler itself, and is or may be afterwards directed to useful purposes." This latter plan, namely, the vibrating cylinder, looks well in theory, but we fear in practice it would be found very imperfect. Reciprocation, as we have shown, is a great destroyer of power, and here the whole engine, boiler, water, cylinder, fire-grate, and all the apparatus, are constantly moving backwards and forwards, and all this, too, merely to dispense with the guide wheel and connecting rod. Mr. Matthew Murray, of Leeds, obtained a patent for a Portable Engine, in 1802, which displays much novelty and ingenuity. The annexed figs. 1. and 2. represent front and side views of the combination of parts of this engine. "A the steam cylinder; B the piston rod; CC, connecting-rods, for connecting the piston rod to the pin in the wheel D; E a wheel, fixed to the side of the cistern I, with the teeth inwards, to admit the teeth of the wheel, D, for the purpose of giving a parallel direction to the rods, CC; F a plain wheel, upon the fly-wheel shaft, G; the wheel, F, is furnished with a double conical centre, for the wheel, D, to run upon; I is a cistern or frame of plates, on and in which the whole combination of materials constituting this engine is fixed; K K two wheels, |