common gas tubes, in which the seams are formed by bring ing 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 tous 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 obstacles in the road. This guiding action being administered with a multiplying power, through the complex medium of toothed-wheels, was found to be far more effectual and convenient, than when a long lever of a more simple form was used; besides that the latter was somewhat dangerous to the guide, who was rendered liable to receive severe blows by the motion of the long handle, when the wheels happened to be turned aside by the opposition of stones lying in the road. At m is a lamp, not only useful for lighting the road before the carriage, but serving also (as the prow of a vessel to a mariner,) to steer by.. The chimney-funnel was made double, the space between the external case n, and the internal smoke flue o, being for a current of air to prevent the otherwise unpleasant radiation of heat laterally. The fuel preferred was a mixture of coke and wood charcoal, which produced a good heat, and gave off but little black smoke. The motion was communicated to the separate axles of the hind wheels by spur-gear of two velocities, changeable at pleasure, as the state of the road or other circumstances might require: this gear was enclosed in boxes, as shewn at h, and the whole machine was placed upon springs, except the guiding apparatus, which was purposely arranged otherwise, as exhibited in the engraving. The body of the carriage was placed no higher than necessary to obtain security from overturning, and the most perfect safety from personal danger by the sudden extrication of steam, should it happen that a tube were to burst, which was barely possible. In the numerous experiments made with this carriage, in which the writer had an opportunity of riding, the greatest speed obtained upon a level, on a very indifferent road, was three miles in twelve minutes, (which is at the rate of fifteen miles the hour,) and that was the greatest distance ever ran by it, without some accident occurring to the machinery. The vibration of the parts, either injured or broke something; but what was almost uniformly the case, some of the joints or connexions of the |