period a motive for preferring the other; and this wear was considerable at first, owing to the narrow surface of the rails; afterwards, when the bearing of the rails was made greater, and now, since the introduction of case-hardened wheels, this objection is entirely removed. Certainly, when the wheels were indented, the increase of friction would almost amount to the difference between the two rails, and this might cause an uncertainty which of the two to be preferred. This having ceased, and the other reasons for preferring the edgerail still remaining good, together with the saving of weight, by the more proper distribu

tion of the metal to resist the transverse strain of the carriages, renders it no longer a subject of dispute that the edge-rail is decidedly the best.

CHAPTER II.

OF CARRIAGES ADAPTED TO RAIL-ROADS.

It is very obvious that the form of the carriages will depend, in a great measure, upon the nature of the goods to be conveyed in them; many kinds of goods requiring a different sort of carriage. To attempt to give plans of the different forms of carriages to be used upon Rail-ways would be an endless task; I shall, therefore, confine myself principally to the description of the wheels and axles, or other parts, which the nature of the road require should be always of the same form and construction.

The carriages, or, as they were termed, waggons," used in the first introduction of Rail-ways, were, and still remain, where employed in conveying coals, the frustrum of a pyramid, or in the shape of a hopper; being much broader and longer at the top than at the bottom: the Rail-roads almost universally descending towards the depôt, the fore-wheels were made of greater diameter than the hind

;

wheels, according to the angle of the road the object being to keep the waggon in a horizontal position; the fore end of the waggon, resting on the large wheels, was also made to project considerably further beyond the perpendicular line of the axles of the fore than the hind-wheels, so that the centre of gravity of the load was not midway between the wheels, but much nearer the large wheels than the smaller, and, consquently, laying a greater weight upon them than upon the latter. This form of the waggon has gradually given way to wheels of the same size, and the body of the carriage square, and placed equally upon the two axles, as shown in Fig. VII Plate IV.

The wheels were, for a long period, made of wood, composed either of one entire piece, or of two or three pieces fastened together. The mode of making the latter was by joining the pieces together by wooden pins, and securing them by flat slips of iron, in the shape of an S, nailed upon the line of the joining. The periphery of the wheels was hewn into the proper shape, by the workmen, with the axe, with a projection on one side to keep them upon the rail. The axles were made of wrought-iron, and fixed firmly into the centre of the wheels, and, consequently, turned upon

the bearing with the wheels. From the very probable inaccuracy of the workmanship, it is not likely the periphery of the wheels would be perfectly circular, which would cause a sort of jolting or undulatory motion to the load, and thus increase the draught.

To one side, or, in some instances, when steep declivities were to be descended, to both sides of the waggon a brake or lever was attached, which was made to press upon the wheels of the carriage, and regulate the velocity.

a, b, Fig. VII. Plate IV. Is the brake or lever, which is called a "convoy;" it is fixed upon the bolt or pin d, projecting from the frame of the carriage A B, which serves as a fulcrum; upon the brake at c c are attached two pieces of wood, which, when the end b of the lever is depressed, acts against the wheels and checks their velocity. At first, these convoys did not extend beyond d, acting upon the hind-wheels only as a lever of the second kind; and when very steep declivities are to be passed there were two, one on each side, united together at the end b by a bar of wood or iron ́extending across that end of the waggon, thereby enabling one man to work them both: it was a comparatively modern improvement to extend the lever beyond d, and thus embrace both wheels.

The arm or lever of these convoys are either made of wood or of iron; when of wood, pieces of beech, c c, called "breasts," are nailed on, which are renewed when worn away when of iron, they are bolted, as shewn in the drawing, the iron being flattened for that purpose. The end b is kept up by a hook, when the convoy is not used, to

prevent the parts c c from touching the wheels. In some cases, another lever is used, to give additional power to the man in pressing down the end b; this is accomplished by fixing it with a chain upon the frame of the carriage, the chain acting as the fulcrum; another chain, a little from this, reaches to the end b, to which it is attached, so that by pressing down the end of the second lever, which is prolonged for some distance behind the end of the waggon, the required purpose is effected.

It seems uncertain at what precise period cast-iron wheels were first introduced. In a dictionary of the arts and sciences, published in 1754, a drawing is given of a cast-iron wheel used upon carriages to convey stones from a . quarry near Bath, said to be "a great improvement in some carriages and waggon-ways made use of at the coal-mines near Newcastle;" from whence we may suppose they had not been used there at that period. How long after this they were adopted, I cannot learn; but, in 1765, two wooden and two cast-iron wheels were mostly in use, the wooden ones retained for the application of the brake or convoy.

Great reluctance was shewn, even down to a very recent date, to relinquish the employment of wooden wheels; many objections were urged against the others, their liability to break, to cut the rails, their insufficiency to present an adequate hold to the brake. At first the castiron wheels do not appear to have been pro