they form a circular rim, on which the flanged tire is laid. Thus, in Fig. 4, the end of the spoke a, is bent at 1, in the manner shewn in the drawing; and from 1 to 2 forms a portion of the inner rim, the spoke, b, forming a continuation from 2 to 3, and so on, until the circle is complete; the end of the spoke 1, resting on the elbow-bend of the end 2 of the spoke b, and the end of b resting upon the elbow-bend of the spoke c. This is shewn more distinctly, on a larger scale, at D. When, therefore, the bent spokes are thus laid upon the ends of each other, they form a circular rim; the tire is then heated, and laid upon the rim, and, when cooled, the contraction of the iron presses the ends of each spoke firmly upon the elbow-bend of the next spoke, and thus forms a perfect wheel. The under side of the outer tire is rolled concave, with a slight bead, or projection, on each side, shewn at dd, in в, Fig. 4. expansion of the rim, or tire, when hot, allows the inner rim, or spokes, to pass within the projecting bead; and, when the tire contracts, it secures the inner rim firmly within the side beads.

The

ABC, Fig. 5, is another form of this description of wheel, which is called the sector-spoked wheel, each spoke being a sector of a circle. In the construction of this wheel, the ends of the bar of iron, forming the spokes, are inserted into the nave, in the usual manner, being first moulded into the form shewn in the drawing, and the other ends bent into the form of a section, as shewn in the drawing; and, being laid against each other, forms a continuous circle, or rim, upon which the flanched tire is laid, as before described. This construction of the spokes forms a very firm and complete wheel. There are many other modifications, in the construction of this description of wheel, described by the patentee; but those shewn in Figs. 4 and 5, have

been mostly used. This kind of wheel, being formed entirely of wrought iron, except the nave, and the intermediate rim being of wrought iron, it is peculiarly adapted for railways, where the rate of travelling is very great, as there is no risk of breakage, if the material be of good quality; and if the velocity is so very rapid, that the tire becomes heated, and expands, the elasticity of the spokes is quite sufficient to counteract any effect of this kind, and to preserve the stability of the wheel. They have been, almost exclusively, used on the recently made carriages on the London and Birmingham, Grand Junction, and Liverpool and Manchester railways. Several modifications of this form of wheel, have been attempted; but as these are, generally, more in the shape of evasions of the patent, than improvements in the construction of the wheels, we do not conceive it necessary to describe them; more especially as few, if any, have been, as yet, used by the different railway companies.

§ 6. Form of Axles, and Bearings.

The axles, and plan of bearings, or chairs, come next under consideration. For many years after the introduction of cast-iron wheels, the axles, wheels, and plan of bearing were uniformly of one description, for carriages on edge-rail roads. Figs. 1 and 2, Plate VII., shew an improved form of the waggons, now almost exclusively used for the conveyance of coals on private railways. The wheels are all of the description shewn in Fig. 1, Plate VI., with a square hole in the nave, into which the ends of the axles are wedged; the bearings are all within the wheels, and consist of a cast or wrought iron chair, secured to the framing of the carriage by bolts, with a semicircular bearing for the axles. In the early stage of railroad mechanism, the chair, or bearing, was made extremely narrow, not

more than one inch and a quarter in length, and in breadth not equal to the diameter of the axles. It was made thus, under an impression, that the narrowest bearing produced the least friction. Subsequent experience has shewn this to be quite erroneous, and experiments will be hereafter given, which shew this, in a very conspicuous point of view. The length of the bearings is now never less than three inches, but more frequently greater.

Fig 4, Plate VII., shews an improved plan of this kind of bearing, which is much used, for carriages of the description of Figs. 1 and 2; a a, are the bolts which secure the chair to the framing of the carriage, b b, the upper part of the chair, with a semicircular bearing, e, representing the end of the axle. Until recently, the lower side of the axle was exposed, and the dust of the railroad operated very injuriously to the progress of the carriages; a cap, d, is now fastened by the bolts, 1 1, to the upper part of the chairs, which protects the axle from the dust of the road. The oil is applied to the upper side of the axle, through the hole, 2; and there are two modes of securing a continual supply of oil, or other lubricating matter, to the axle. When oil was used to lubricate the axles of the carriages, on the Liverpool and Manchester railway, the plan introduced by Mr. Stephenson, was a tin box, containing the oil, placed upon the frame-work of the carriage, from which a piece of cotton wick proceeded, and which was inserted down the hole, 2, Fig. 4; and which, acting as a syphon, kept up a continual supply to the axle. The other plan, which was first introduced by Mr. Booth, was, to use such a description of lubricating matter, as would melt with a moderate degree of heat. This was placed in a box, in the frame-work of the carriage, immediately above the bearing of the

axle, with a hole to communicate therewith ; the lubricating matter was, therefore, constantly in contact with the axle; and when the latter became in the least degree heated, for want of oil, the heat produced a fresh supply. Mr. Booth has a patent for a kind of lubricating substance of this description, which consists of a solution of the common washing soda of the shops, in the proportion of half a pound of the salt to a gallon of pure water; to one gallon of this solution, three pounds of good clean tallow, and six pounds of palm oil are added; or, instead of the mixture of palm oil and tallow, ten pounds of palm oil, or eight pounds of firm tallow. The whole mixture is heated to about 200° or 210° of Fahr., and well stirred, or agitated, until the composition is cooled down to 60° or 70° of Fahr., and has obtained the consistency of butter, in which state it is ready for use.

The kind of bearing, previously described, is used where the wheels are on the outside of the frame-work of the carriage, or where the bearing is on the inside of the wheels. In many carriages, and especially those for the conveyance of bulky goods, it is necessary to have a greater width of frame-work, than that which can be obtained within the wheels; and, hence, it is necessary to elevate the frame-work of the carriage above the wheels, and increase its width; in which case the bearings are placed on the outside of the wheels. Independently of the increased accommodation which such a form of carriage presents, there are other considerations, which make a bearing outside the wheels, preferable to one within the wheels. In the latter case, the size of axle is necessarily large to resist the shocks, as well as the direct weight of the load; and when the wheels are of large diameter, the twist upon the axles is very considerable. With inside bearings, therefore,

the chair, or semicircular bearing, cannot be of less diameter than the size of the axle; but outside bearings not being subject to the twisting of the wheels, the diameter of the axle, at the bearing, can be made much less; and, if we suppose the same resistance acting on the surfaces in both cases, the friction should be in the direct ratio of the diameter of the axle at the points of bearing, and, consequently, greater with the inside than outside bearing. Carriages carrying about four tons of goods, and with three-feet wheels, require axles, at least, three inches and a quarter in diameter, which must be the size of the bearings inside the wheels; whereas the outside whereas the outside bearings may be reduced to two inches, and thus diminish the resistance considerably.

Figs. 5, 6, and 7, Plate VII., shew a plan of axle and bearing on the outside of the wheels; a is that part of the axle, on which the nave of the wheel is fixed; bb, shewing a part of the nave, and c the end of the axle, which constitutes the bearing portion; in this bearing, the axle diminishes in diameter in three divisions. Fig. 8, is another plan, which is more generally adopted, than the preceding. Fig. 6, shews a section of the bearing, or chair, through the middle; this chair consists of a cast-iron box, 1, 2, 3, 4, in two pieces, separated at 4', and fastened together by bolts, the holes of which are shewn at 5, 6, on the plan Fig.7; one of the bolts is shewn by the dotted line, d, Fig. 6. The extreme end of the axle, it will be seen, is increased in diameter, for the purpose of preventing the chair from sliding outwards, and, therefore, it necessarily causes the chair to be made in two pieces; ie, ie, are the upper and lower brass parts, which rest on the axle, and surround it, and which are enclosed by the cast-iron chair, 1, 2, 3, 4. A cavity, or chamber, at f, is cast in the chair, to con