diagram, but the internal mechanism will require a section of the engine to shew those parts in detail.

In the annexed diagram, a is the cylinder; b, the main

steam pipe; c, a friction wheel in the centre of the perpendicular frame, which makes the piston move parallel. To the ends of the beam are attached two connecting rods, which work a double crank at the axis, where the motion is communicated by two wheels to the axle, g, to which the propelling wheels are attached; f is a lever by which the valves are worked by the stud on the axis, and i; the two connecting rods which are attached to the end of the lever, work the valve piston, k; d is the common tube slide valve, which is surrounded by steam, supplied from

the main-pipe, where it enters. The lower tube represented as open in the figure, allows the steam to enter under the piston, which is forced up by the steam; at the same time, the steam that was above the piston, escapes down through the tube d, and is at once discharged into the atmosphere. When the engine is to be put in operation, the furnace is charged with ignited charcoal, which soon raises enough of steam to make the carriage move along a rail-road with a number of loaded waggons behind it, round the Lecturer's table, on a circular road, eight feet in diameter.

The preceding diagrams shew the general arrangement of the parts in a locomotive steam-engine on a small scale, and where its velocity is sufficient to carry the whole apparatus along a path without the aid of a fly-wheel. In the ordinary steam-carriage however, it is necessary to employ two pistons working in cylinders connected with the same boiler, and as these act upon cranks at right angles to each other, any required momentum may be obtained without the machinery having its motion checked by the reciprocating action of the working beam.

At the top of Plate IX. a view is given of a steam carriage employed at Wylam Colliery, Newcastle, for which we are indebted to Mr. Hedley, an extensive coal viewer and mineral surveyor in that district. The boiler a, with its connecting frame of wood and iron, is supported by a series of wheels, which rest on the rail road. The furnace mouth and chimney are placed at the same end of the boiler, the flame and heated air taking a circuitous path through the water. A coal-box, b, is intended to supply fuel for the engine during its journey.

The wheels cccc work into each other by means of their connecting teeth, so that when one pair of wheels is put in motion, the whole series revolve on their axis. Two

N

working beams or levers revolve on axes at d, and are attached by a double parallel motion to the piston rods beneath. The piston e is now depressed, and the connecting rod f has pushed the crank into such a position, that it ceases to operate effectually on the impelling wheel. A new impetus is now given to the engine by the second piston and working beam g, so that a continuous rotatory motion is effected, and the carriage impelled forward. The motive for employing so many supporting wheels, is to ensure a sufficient degree of adhesion between the wheels and rail-road that supports them; and also to divide the weight of the engine, and as such prevent its destroying the bars of which the road is composed. The safety valve, which is so essential a part of all steam-engines, is seen at h, and the rest of the apparatus will be sufficiently understood by a reference to our previous description of the engine.

Messrs. William and Edward Chapman have obtained a patent for a mode of effecting the loco-motion of the engine, by means of a chain stretched along the middle of the rail road, the whole length, being properly secured at each end, and at stated intervals. This chain was made to wind partly round, or to pass over a grooved wheel, turned by the engine, of such a form that the wheel could not turn round without causing the chain to pass along with it. When this wheel was turned round by the engine, as the chain was fastened firmly at the end, it could not be drawn forwards by the wheel, the carriage was therefore moved forward in the line of the chain.

The carriages containing the goods were attached to the engine-carriage, and thus conveyed along the rail road.

At intervals of every eight or ten yards, the chain was secured by means of upright forks, into which it fell when left at liberty; this was for the purpose of taking off the

strain from part of the chain, when more than one engine was travelling by it.

The chain was prevented slipping, when the grooved wheel was turned round, by friction-rollers pressing it into the groove. Mr. Chapman had one of his engines tried upon the Hetton Rail-road, near Newcastle, but it was soon abandoned, owing to the great friction which arose from the use of the chain, which would operate considerably against it, and also increase its liability to get out of order.*

A portable high-pressure engine is a desideratum of very considerable importance in the erection of large

buildings, preparing sewers, and other works in which water or ballast is to be raised. On this account we now furnish a view of a small apparatus well calculated for this purpose; and so simple is the arrangement of its parts, that but little of detail will be necessary for a complete illustration of the entire mechanism. The boiler consists of a large cylinder of cast iron, made very strong, and placed with its axis resting horizontally upon short feet or pillars of cast iron: the boiler has a flanch at one of its ends, to screw on the end or cover, which has the requisite openings for the fire door, the man hole, the exit for smoke, and the gauge-cocks. The fire is contained within the boiler, in a cylindrical tube of wrought iron, A, which is surrounded with water on all sides.

At the part where the flue enters the chimney is a small door, to remove any soot that may have accumulated. On the top of the boiler, is a safety-valve, kept down by a lever and weight, to allow the steam to escape in case it becomes so strong as to endanger the bursting of the boiler. The steam cylinder, c, stands in a perpendicular direction, and is inclosed within the boiler, except a few inches of its upper end, at which the four-passaged cock is situated, and the flanch which screws on the lid with the stuffing-box for the piston-rod to pass through. The boiler has a projecting neck, into which the cylinder is received, and it is fastened in its place by a flanch round the upper end of the neck of the boiler, which is united by screws to a flanch projecting from the cylinder at about one-third from its top flanch. The upper end of the pistonrod is fastened to the middle of a cross-bar, which is placed in a direction at right angles, to the length of the boiler, and guided in its ascending and descending vertical motion, by sliding upon two perpendicular iron rods, fixed to the boiler, parallel to each other, being connected