pipe, c, being carried nearly to the top of the chamber, to receive the steam, and being funnel-shaped, or spread out at the top, and nearly filling the chamber, the water is thus separated from the steam, and falls back into the boiler, and the steam alone passes into the steamchamber and cylinders.

The regulator, for increasing or diminishing the supply of steam to the boiler, is placed between the pipe proceeding from this chamber, and the two pipes leading to each cylinder. Fig. 8, shews the regulator on a large scale; c, is the steam-pipe, leading from the chamber, B, and s s, are the two steam-pipes, leading to each cylinder; over the mouth of each of the pipes, s s, a disk, or slide, 1 1, moves back and forwards, alternately closing or opening the mouth of the pipes, as they are moved round. These two disks are fixed upon the horizontal rod, 22, Fig. 1, by which they are turned round; this rod reaches the whole length of the boiler, and, passing through the opposite end, is turned by a handle, 4, as shewn in Fig. 1. It will be seen, that the regulator, a, Fig. 8, is a chamber, with the pipe, c, leading into it from the boiler, and the two pipes, ss, leading from it to the cylinders; and that, as the disk is moved round, the communication is either opened or shut, to the cylinders. These disks are, of course, kept tight against the face of the mouth of the pipes, by the pressure of the steam, but spiral springs are. likewise placed between the arms of the spindle, or rod, 2%, and the brass face of the disk, as shewn in Fig. 8, to keep a constant pressure against the face of the pipes. To resist the contraction and expansion of the rod, 22', as well as to make it steam-tight, in passing through the boiler at the handle, 4; a tube, 33', bored out on the inside, passes through the end of the boiler, and is bolted to it at the end, 3', by a flanch;

the end, 3, of this tube, is conical, into which the rodis made to fit, as shewn in the figure, being pressed steam-tight against it by a spiral screw, fixed within the tube. The rod has a sliding joint at 2, to compensate for the contraction, and expansion, and at the same time allow the disk, at the end, 2, to be pressed tight against the face of the steam-pipes, and the part, 3, steam-tight, at the other end.

As previously stated, in describing the progressive improvement of these engines, the chimney is not of sufficient height or power to create draught of air through the fire, to produce steam sufficiently quick to supply the cylinders, when travelling at rapid velocities; the steam, therefore, after passing through the cylinders, is thrown into the chimney, to create a sufficient draught. t, Fig. 1, shews the pipe through which the steam is thrown into the chimney; an end view of which is shewn at Fig. 11, vv, being the pipes leading from each cylinder, into the single vertical pipe, t, called the "blast pipe."

For the purpose of giving warning to the passengers, that the engine is about to start, or to persons standing or straying about upon the line of railway; a contrivance has been adopted in the shape of a steam-whistle, which produces a very smart and shrill sound, and which can be heard at a very considerable distance. x, Fig. 1, Plates XI. and XII. shews this contrivance fixed to the boiler, within reach of the engine-man. Fig. 11, Plate VI. shews the construction of this, on a large scale, which consists of a pipe, fastened to the top of the boiler, by the flanch or plate, a a; a cock, b, is placed in this pipe, which being opened or shut, allows or prevents the steam from issuing through this pipe; when open, the steam passes into the hollow cup or chamber 11, through the apertures of a plate, shewn in

the plan, 22, and which is placed upon the pipe, at its opening into the bottom of the chamber, 11. The steam then passes around the plate 3 3, between its edge and the side of the cup, 1 1, and, striking with great force against the thin edge of the cup, 44, produces a most powerful, sharp, and shrill whistle.

Fig. 12, Plate VI. is a vacuum valve, for the purpose of allowing the steam to escape out of the boiler, when the pressure is very low, and when the boiler is required to be emptied of steam; they are sometimes attached to the cylinder, and sometimes to the boiler, by the flanch, a a; as will be seen, it is a mitre valve, opening inwards, and, consequently, so long as the steam is above the pressure of the atmosphere, the valve is shut, and prevents its escape. There is, however, a spring in the inside of the valve, which is acted upon by the plate, i, fixed upon the upright spindle, passing through the top of the valve. Upon this spindle, there is a spiral thread, with a nut on the outside of the valve, at c; when, therefore, this screw is turned, the plate, i, presses against the spring, and, acting on the valve, forces it down, and then allows the steam to escape. When in use, by causing the spindle to act upon the spring, any degree of pressure is kept upon the valve, and, therefore, when the steam gets below that pressure, it escapes, and gives notice to the engine man, that the steam is below the proper degree of elasticity.

Fig. 13, Plate VI. is a syphon oil cup, for the purpose of keeping up a regular and constant supply of oil to the various working parts of the engine; it is fastened to the parts where required by the screw, a, the oil being put into the chamber, b, of sufficient quantity to serve a journey, or day's work, of the engine; it is made to feed down upon the bearing by a cotton wick.

Fig. 15, Plate XI. is a valve, or ball-clack, which is used for the force pumps supplying the boiler with water. From a to b, is a pipe, on the top of which, at a, it is mitred, and the ball rests upon this mitre; the upper part being open from a to c.

Mode of admitting the Steam into the Cylinders, and of working the Engine.

Having thus described the form and construction of the boiler, and the manner in which the steam is generated, we have now to explain the mode of transmitting the steam into the cylinders, and the plan of producing the locomotion of the engine. The cylinders, as previously stated, are placed horizontally, as shewn in Fig. 1, Plate XI., and in the same plane with respect to each other; A, Fig. 1, representing one cylinder, and D, Fig. 3, the other. These cylinders are fixed to the frame-work of the boiler, and, being within the chamber, into which the heated air from the tubes is thrown, in its passage to the chimney, they are always kept at a high degree of temperature. 5, and 6, are the pistons, 55, being the piston-rod, and 59, the connecting rod, of one cylinder; and 6 6, the piston-rod, and 6 10, the connecting rod, of the other; the former represents the connecting rod and crank, in a line with the cylinder, and the latter the crank, at right angles with the line of the cylinder.

The parallelism of the piston-rod is effected generally by the use of slides, as being most convenient for this description of engine; 8 8, Figs. 1 and 3, are the stuffing boxes or glands of the cylinders; and Figs. 12, 13, and 14, shew the slide-bars, constituting the parallel motion for the piston-rods. a, b, c, d, Fig. 13, is an end view of the two plates, fixed parallel with the line

of the centre of the cylinder, and crank axle. Fig. 14 is a plan of the same plates, the upper ones, cd, being removed to shew the slide; e e, is the cross-bar to which the piston-rod, 6, is attached, as shewn in Fig. 12; and to which the end of the connecting rod, 10, is likewise attached, as shewn in Fig. 14; this cross-bar is inclosed within the brass carriage, 1, 2, 3, 4, Fig. 13, resting on 1, 2, as shewn in Fig. 14; and 3, 4, forming the cover; this carriage slides within the parallel plates, a, b, c, d, and thus the parallelism of the ends 5, and 6, of the piston-rods, is effected, while the stuffing-boxes, 88, and pistons, preserve the rectilinear motion of the other end. One end of the connecting rod, therefore, keeps up an alternating rectilinear motion, and the other, by means of the crank, a continued rotatory motion, by which means the locomotion of the engine is effected. We have said, that the drawings shew one of the cranks in a line with the centre of the cylinder, while the other is at right angles with it; this is necessary to secure a continued and certain rotatory motion to the wheels, and to accomplish this, it is necessary to have two cranks upon the driving axle of the engine. Figs. 9 and 10, Plate XI. are two views of the axle, upon which the propelling or driving wheels are fixed, which move the engine. This axle is cranked in two places, at E, and F, as shewn in the two drawings; a a being the part where the chair rests upon, and bb, that part whereon the wheels are fixed. The axle is cranked in such a manner, as that when one crank is horizontal, the other is vertical, and vice versâ, being at right angles with each other; thus, in Fig. 9, the crank, E, is horizontal, and F, vertical; and in Fig. 10, the crank, E, is vertical, and F, horizontal. The cause of this, as explained previously, being to ensure a continuous rotation to the wheels, by either