[STEAM CARRIAGES AND RAILWAYS.]
No invention of the present century has produced so great a social change as Steam Locomotion on railways. Not only have places that were formerly more than a day's journey from each other been made accessible in a few hours, but the cost of travelling has been so much reduced, that the expense has in a great degree ceased to operate as a bar to communication by railway for business or pleasure.
Though the coaching system in this country had attained the highest degree of perfection, a journey from London to Liverpool, previously to the formation of railways, was considered a serious undertaking. The "fast coach," which left London at one o'clock in the day, did not profess to arrive in Liverpool till six o'clock the following evening, and sometimes it did not reach there till ten o'clock at night; and the fare inside was four guineas, besides fees to coachmen and guards. The same distance is now performed in six hours, at one-third the expense, and at one-fourth the fatigue and inconvenience.
Railway Locomotion, however, forms no exception to the rule, that most modern inventions have their prototypes in the contrivances of ages past. They were used upwards of two hundred years before locomotive engines were known, or before the steam engine itself was invented. The manifest advantage of an even track for the wheels long ago suggested the idea of laying down wood and other hard, smooth surfaces for carriages to run upon. They were first applied to facilitate the traffic of the heavily laden waggons from the coal pits; the "tramways," as they were called, being formed of timber about six inches square and six feet long, fixed to transverse timbers or "sleepers," which were laid on the road. These original railways were made sufficiently wide for the wheels of the waggons to run upon without slipping off; the plan of having edgings to the rails, or flanges to the wheels, not having been adopted till a later period. To protect the wood from wearing away, broad plates of iron were afterwards fixed on the tramways.
Cast iron plate rails were first used in 1767. The flat plates on which the wheels ran were made about three inches wide, with edges two inches high, cast on the near side, to keep the wheels of the "trams" on the tracks. These iron plates were usually cast in lengths of six feet, and they were secured to transverse wooden sleepers by spikes and oaken pegs. The tramways were laid down on the surface of the country without much regard to hills and valleys, the horses that drew the trains being whipped to extra exertion when they came to a hill, and in descending some of the steep inclines, the animals were removed, and the loaded waggons were allowed to descend the hills by their own gravity, the velocity being checked by a break put on by a man who accompanied them.
The chief use of the tramways was to facilitate the conveyance of coals from the pits to the boats; and as the level of the pit's mouth was higher than that of the water, it was an object, in laying down a tramway, to make a continuous descent, if possible, for the loaded trains to run down, the dragging back of the empty ones being comparatively easy. Thus, though "engineering difficulties" were not much considered in the construction of those early railways, engineering contrivances were adopted to diminish the draught, by making the gradients incline in one direction.
Soon after the invention of the Steam Engine had been practically applied to mining purposes, its power was directed to draw the coal waggons on railways. This was done about the year 1808; and, in the first instance, the application of steam power was limited to drawing the loaded waggons up steep inclines. A stationary engine was erected at the top of the incline, and the waggons were drawn up by a rope wound round a large drum. This mode of traction was afterwards extended, in many instances, along the whole railway, so as to supersede the use of horse power. The employment of stationary engines in this manner was continued, even after the invention of locomotive steam engines, to draw the trains up inclines that were too steep for the power of the small locomotives at first used to surmount; nor has this plan been yet altogether abandoned.
The application of steam to the direct propulsion of carriages was a comparatively slow process. It was, indeed, contemplated by Watt, as a substitute for horse power on common roads, though he does not seem to have contrived any means by which it might be done. The first known application of the kind was made by Mr. Murdoch, an engineer in the employment of Messrs. Boulton and Watt, who in 1784 constructed a working model of a steam carriage, still preserved, and which formed one of the most interesting objects in the Great Exhibition of 1851. The boiler of this model locomotive is made of a short length of brass tube, closed with flat ends. The furnace to generate the steam consists of a spirit lamp. The steam is conducted directly from the boiler to a single cylinder, which is mounted on a pivot near the centre, so that by the movement of the cylinder the piston-rod may adapt itself to the varying positions of the crank. The two hind wheels are fixed to the axle, and on the latter is the crank, attached to the piston-rod. A single wheel in front serves to guide the carriage, which is propelled by the rotation of the two hind wheels. The elastic force of the steam is directly applied as the moving power; and after it has done its work in the cylinder, it is allowed to escape into the air.
This first known application of steam as a locomotive power is more perfect in its general arrangements than many steam carriages that were subsequently brought into operation; and in the plan of balancing the cylinder on pivots, we perceive the origin of the oscillating engines, which have been recently introduced with much success in Steam Navigation. By that arrangement there is attained the most direct application of the piston-rod to the crank, with the least loss of power.