different it is from that of a carriage moving upon the hard and almost perfect plane of an iron railway, which allows the wheels to roll with undeviating regularity, and with only a very slight resistance. On the common paved and gravelled road, the varieties of the surface cause a constant succession of violent concussions and vibrations of the machinery, rendering those parts that are connected liable to be strained or broken, and those that work near together, to strike or rub against each other. In every experiment some defect is discovered; then the alteration of one part generally entails the alteration of another, and each successive alteration is scarcely made, than the active mind of the inventor discovers something better, and another arrangement of parts is the result. Thus, while improvement succeeds improvement, time proceeds, which induces those persons, who know nothing whatever of the subject, but who wish to appear sagacious, to assert success to be impossible, and to ridicule every attempt to attain it. It happens, too, sometimes, that deterioration, instead of improvement, takes place by the successive alterations, and thus the original strongly-framed machine gets cut to pieces, and requires numerous patchings and bracings, that do not confer an adequate strength to compensate for the increased weight.

A four-wheel locomotive carriage, possessing all these disadvantages, and weighing nearly three tons, was started on the 5th March, 1829, on Epping Forest. This ponderous mass of iron and wood was provided with two working cylinders of only 3 inches in diameter, the power of which was applied to the hind-wheels. The steam was supplied by two tubular boilers, each forming (by the arrangement before described) a hollow cylinder, four feet six inches long, with an internal diameter of one foot nine inches, where the fire was made. With this apparatus the carriage, loaded with fifteen passengers, was propelled several miles on a rough gravelled road, across Epping Forest, with a speed varying from twelve to fifteen miles the hour. It should here be observed that the tubes of which the boilers were composed, were the

common gas tubes, in which the seams are formed by bringing the edges together, where they are welded. This process of welding is effected by machinery with great rapidity, and although it answers very well for cold gas at the ordinary pressures, is not adapted for sustaining the pressure of very high steam, together with the effects of the fire, and was only employed in the present instance as a temporary experiment, which also proved its inadequacy, by the seams of one of the tubes opening, and letting the water out of one of the boilers, extinguishing its fire and reducing the intensity of the other, there being a communication between them. Thus circumstanced, with only one boiler in operation, the carriage returned home, at the rate of about seven miles an hour, carrying more than twenty passengers,—at one period, it is said, a much greater number; shewing that sufficient steam can be generated in such a boiler, to be equal to the propulsion of between five and six tons weight.

In consequence of this flattering demonstration that the most brilliant success was attainable, the proprietors dismantled the carriage, and commenced the construction of superior tubular boilers, in which the tubes were of the same internal diameter (one inch), but of greater strength, being three-sixteenths of an inch thick, and the seams welded with a good overlap. Here, however, a new source of vexation took place, from the proprietors not being practically experienced in the quality of iron proper for such purposes, which should be either the very best charcoal iron, or a quality similar to that manufactured by Messrs. Adams, of "Wednesbury Forge," and distinguished by the term best box-plates, being used for making the wrought iron boxes to coach wheels. Iron of this kind is so exceedingly tough and malleable, as to" work like lead" (as smiths significantly describe it), under the hammer. The "best London scrap," the "B B," and many other sorts, that are recommended by dealers as of "superior" quality, are decidedly unfit for making tubular high-pressure boilers, wherein the tubes are much bent. Every boiler manufactured by Messrs. Anderson and James, of other kinds

of iron than those above recommended by us, failed; that is to say, fissures were either opened in the bending of the tubes to the required form, or were subsequently opened in the working of the boilers, so as to render them unfit for the object designed. From these causes, great delays and expenses were incurred, and it was not until the month of November 1829, that a small carriage was brought out, represented by the sketch on the preceding page.

The figure exhibits a side elevation, and from its diminutive size, (as shown by the scale) was not intended to carry any inside passengers, but to be employed to drag another carriage behind it. The boilers, four in number, were wholly of wrought-iron tubes, three-fourths of an inch in diameter; and although on the same principle as Mr. James's boiler, previously described, the form of each (instead of circular,) was that of an oblong ellipse, in an upright position, for the purpose of getting as large a surface of metal as possible exposed to the heat of the furnace; as by this arrangement, nearly two hundred tubes, measuring upwards of four hundred feet, were inclosed in a space four feet wide, three feet long, and two feet deep, including the furnaces, (which were inside the boilers), besides the flues and ash-holes. The steam from each of the boilers was conducted into one very strong tube above, of an inch and a half diameter, to supply the engines; each of the pipes of communication to it being provided with stop cocks, to cut off the communication of any boiler that might become unserviceable by leakage, without affecting the pressure on the other boilers. The power was applied through the medium of four working cylinders, which might be considered as separate engines, being fitted so as to work independently of each other, although they might more properly be considered as pairs, each pair acting upon a distinct crank, (the throws of which were at right angles to each other,) that gave motion to its respective hind wheel, on the principle described at page 531. These cylinders were only a foot long, three inches and a half outside, and two inches and a quarter inside, diameter; the pistons were metallic,

making a nine-inch stroke. The cylinders were posited vertically, and vibrated upon trunnions, through which were made the induction and eduction passages, covered by conical valves, forming an external shell to the trunnions, close to their bearings in the plummer boxes.

These engines were arranged at a, in a row across the carriage. The steam, after working the engines, passed through two copper tanks, which heated the water therein to such a temperature above boiling, as to melt the soft solder externally upon the vessels, and rendered it necessary to substitute hard solder; the steam was carried thence to the chimney-funnel to escape. At c is a door, which space across the carriage, and also that at d, were for the use of the man who attended to the furnaces and boilers, besides being used as a receptacle for fuel; at the sides, roof and bottom of this room were plate-iron shutters, to afford constant draughts of air, as the heat would otherwise become insupportable. The engineer sat on the hind seat p; and at e, over the engines, was a sheet-iron flap, like the lid of a box, and at ƒ sliding doors, enabling the engineer to keep his eye upon the working parts, and by his spanners and other tools to rectify, if required, any slight defect that might take place; his situation likewise permitting him to give directions to the furnace-man, and to hold communication with the guide, who sits on the box q. At h is the steering apparatus, consisting of an external case, containing a vertical shaft, at whose upper end is fixed a bevelled pinion, which is acted upon by a small bevelled wheel fixed into the axis of the double-handled winch i i. By turning these handles, therefore, the shaft is caused to revolve, and to give motion to gear at the lower extremity, which acts upon a toothed sector 1, attached to the fore axletree, and thereby turns the fore wheels into the required positions. The lower gear, which is contained in a box k, is adapted to increase the force with a reduced motion, so that the guide, who is able to turn the handles i i quickly, operates with great energy upon the toothed sector, and to overcome with facility the most prominent of ordinary 24.

4 c