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

(Plan of Trevithick & Vivian's Vibratory Engine, and its application a a Sugar-cane Mill. 1802.)

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 workman 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 > 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; C C, 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,

one upon the fly-wheel shaft, G, the other upon the crank shaft, L; these wheels and crank are for the purpose o working the lever, R, in fig. 2, which lever gives immediate motion to the air-pump, P, and the cold and hot water pump; T is an iron bar for supporting the shaft; M is a slide valve for opening and shutting the communication of the steam pipes, marked N N N, and is described in figs. 3, 4, 5, 6, and 7; a motion for the slide valve is taken from the crank shaft, L, by levers, or otherwise, as the nature of the valve may require. The parts so combined form a perfect engine, without requiring any fixture of wood, or any other kind of framing than the ground it stands upon, which is transferable without being taken in pieces, the motion of the fly-wheel shaft giving circular power to any process or manufactory requiring circular motion, or irrigating land, or for the various purposes of agriculture. Figs. 3, 4, 5, 6, and 7, represent various forms of the new slide-valve, in its application to the steamengine; the principle of which consists in moving in a circle, part of a circle or straight line, by means of flat surfaces or faces (or nearly so) sliding or moving upon each other, for the purpose of uniting the necessary apertures in the steam pipes or cylinders. or cylinders. Fig. 3. is a view of a circular flat sliding valve; the dotted lines show the avenues to the steam pipes. a 1, is a figure representing the upper or moveable part of the slide valve, fig. 3. where the conducting or uniting cells are formed: there is a circular spring for compressing a 1 to the face of the slide valve in fig. 3, so as to render them perfectly steam and air tight, which perfection they will naturally acquire by constantly rubbing upon each other. Figs. 4, 5, 6, and 7, show four varieties of the slide valve, for working double or single powers. a 2, a 3, a 4, and a 5, contain the cells for conducting to the different apertures or steam ways. Any further description is unnecessary, as the drawings will convey to any one the principles of these inventions."*

Specification of Patent.