Various opinions exist not only about the preferable form of rails, and modes of fixture, but also regarding the weight or load proper to be carried upon them. This was long regulated at the Newcastle collieries, by making the wagon a measure of capacity connected with the duty on the chaldron of coals carried coast wise; when the wagon and its load were made to weigh about four tons. The inconveniencies of these ponderous vehicles were for a long period little attend ed to, especially on the tram or wooden railways, laid with their whole length bearing upon the ground. But when the expense of a metal railway, capable of sus taining such loads, came to be considered, the pro priety of using smaller wagons was obvious. Such heavy loads are attended with much inconveniency; they distort the" best laid rails by shaking the whole fabric of the road, and ultimately produced much more friction than the introduction of a few additional axles in the use of smaller wagons. When the wheels of such vehicles get off the tracks, it becomes often a work of great difficulty and stoppage to replace them. WVc are, therefore, of opinion, that a load of from one ton to a ton and a half, independently of the weight of the wagon, should be the maximum upon four wheels. The axles of the wagons should be made straight, and the wheels set at right angles upon them, and care taken that the whole is strong enough, not only for working with a precise weight, but for sus• taining the casualties of the road. Railway wagons should not exceed the weight of ten or twelve cwt.; they are generally made of hard wood, and sometimes of plate iron; they ought to be of a square form, with perpendicular sides, rather low and broad, which will make them tpavel more steadily in stormy weather than when they arc high. To carry a ton and a half of coals, for example, they will measure about six feet in length, four feet in breadth, and 1 foot in depth.
In the formation and superintendence of public rail ways, it is obvious that considerable attention ought to be given to enforce suitable regulations as to the height and construction of the wagons. In many instances, railway wagons may be advantageously hung upon springs. It seems also a simple and economical me thod to have the body of the wagon, containing the weight, hung on chains, allowing it a natural swing when any irregular motion or unexpected obstacle oc curs.
Regarding the size of wagon wheels, and their con nection with the axle, various opinions exist. Some have the wheels fixed dead upon the axles, like the an cient cars, or those still in use in the Irish cart. Others have both wheels and axles fitted for rotatory motion. But the more general, and we would say preferable mode, is to have the axle fixed and the wheel revolving. On a railway, where obstacles are not supposed to be met with, as on the common road, the wheels are made comparatively small, which affords a rising or favoura ble line of traction. To determine this point beyond dispute, and also to ascertain the friction upon axles of various dimensions upon the great scale, would resolve an important problem in mechanics. Perhaps a railway wheel of fifteen inches diameter, ought to be considered the minimum, and thirty inches the maximum size. These dimensions are favourable to the yoke, and to the purposes of loading and discharging, while to exceed them would add to the weight of the wagon without obtaining much advantage. Wagon wheels are gene rally made of cast iron. To prevent their wearing un equally, Messrs. Stephenson and Losh, of Newcastle, obtained a patent for hardening the rims of railway wheels.
It has long been a desideratum in the construction of wheels and axles to preserve the grease, and at the same time exclude the dust of the road. This has, in
a great measure, been effected in mail coaches, and other carriages, which travel at speed, but has been less attended to in vehicles which move at a slow pace. The consequence is, that upon railways the grease may often be seen dropping with fullness from the linchpins of one wagon, while the dry axles of another announce its progress upon the road by the most discordant sounds. Mr. Taylor, seeing the disadvantage of this state of things on the railways at his coalworks near Ayr, encouraged his millright in devising a remedy for this evil, which has at length been effected in a very simple manner, by which he is enabled to have the outward end of the nave of the wheel close, as delineat ed at letter e in Fig. 3. Plate CCCCLXXVII. the com mon linchpin, shown at e, Fig. 2. being dispensed with This is effected by means of an appendage fixed to the axle at d, Fig. 3. which we shall teitn a lever linch, the extremity of which at e falls into a groove cut on the nave of the wheel marked e e', which keeps it in its place. Letter f is a swivel bolt, which keeps the lever-linch d and e' into the groove e e' above alluded to. A model of this apparatus has been pre sented by Mr. Taylor to the Highland Society, that the person to whom he gives the merit of the invention may meet with some encouragement, and that the public may be put in possession of this improvement. In practice, however, it may perhaps be found that additional trouble will attend the exact adjustment of the wheels to the axle, which, for the prevention of friction both in the socket or bush of the wheel, and in the groove of the new lever•linch is a matter worthy of due attention.
In concluding this article, we cannot help remarking that the time is not very remote, when from ten to fifteen cwt. was considered a lair load for an ordi nary horse upon the common road. But by recent improvements in the line of draught, and the smooth ness of the surface, this load has been at least doubled. Further, by the introduction of the railway system, we now speak confidently of a single horse doing a day's work, upon a level line of edge railway, with as many tons as he formerly did with hundred weights on the common road. Nor is this all ; for the Trevethic, or high-pressure-engine, has been mounted upon a rail way carriage, and made to drag upwards of fifty tons of coal, exclusively of the weight of the wagons. Where the draught is upon an inclined plane or up hill, a row of cogs or teeth must be laid along the outside of one of the rails, into which a wheel, with corresponding teeth, is made to work, and being im pelled by the steam, the engine-wagon gives motion to the whole train. Upon a level road, or when the acclivity is very little, the wheel with teeth is not found necessary, and in that case the power is communicated immediately to the common wheels of the steam-wa gon ; but in wet weather, when the friction is less, the wheels of the steam-wagon sometimes revolve with out dragging its load or moving progressively. This contrivance has now been a good many years known to the public, and has been suggested as applicable to carriages travelling at speed, even upon the common road, but as yet it has not become general in any form. We are, however, happy to see that it is still regarded favourably by the public, and have every reason to hope that time and practice will render it more perfect ; be ing that description of machine which speculation can not complete, and which practice alone will bring to maturity.