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 aud 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. 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.

This ingenious apparatus, though possessing much merit, infringed, it appears, on the patent right of Messrs. Boulton and Watt, and the patent was, therefore, repealed in 1803. An engine on this plan has been at work many years at St. Peter's Quay, on the river Tyne, and is found to answer uncommonly well.

Mr. Woolf's very excellent and ingenious boiler (patented in 1803) comes next under our notice. The great utility of this apparatus induces us to give the specification, togethe with Mr. Woolf's own remarks, in full.

"Mr. Woolf's improved apparatus consists, first, of two or more cylindrical vessels properly connected together, and so disposed as to constitute a strong and fit receptacle for water, or any other fluid intended to be converted into steam, whether at the usual heats, or at temperatures and under pressures uncommonly high; and also to present ap extensive portion of convex surface to the current of flame or heated air or vapour from a fire. Secondly, of other cylindrical receptacles placed above these cylinders, and properly connected with them, for the purpose of containing water and steam, and for the reception. transmission, and useful application of the steam generated from the heated water, or other fluid. And, thirdly, of a furnace so adapted to the cylindrical parts just mentioned, as to cause the greater part of the surface of all and each of them, or as much of the said surface as may be convenient or desirable, to receive the direct action of the fire, or heated air and vapour.

"One of his boilers, in its most simple form, consists of eight tubes, made of cast-iron, or any other fit metal, which are each connected with a cylinder placed above them. The fuel rests on the bars, and the flame, heated air, and vapour, being reverberated from the part above the two firstsmaller cylinders, goes under the third, over the fourth, under the fifth, over the sixth, under the seventh, and partly over and partly under the eighth small cylindric tube. When it has reached the end of the furnace, it is carried to the other side of the wall, built under and in the direc. tion of the main cylinder and then returns under the