"But these scantlings of iron (as I may call them) were not such as those which are now laid in some places ; they were about five feet long, four inches broad, and one inch and a quarter thick, with three holes, by which they were fastened to the rails, and very complete it was both in design and execution. Hence it was not difficult, if two persons on horseback should meet on this road, for either to turn his horse out of the road, which, on the railways now introduced, would be attended with some serious doubt as to the consequences. But it would be impossible on the best railways to afford that facility of travelling which we now enjoy on a spacious well-managed road ; and in my opinion would prove of greater detriment than all the obstacles we have to deplore in the present un, comfortable state of the roads." We have extended our extract from Mr. Hornblower's letter thus far, to show, that however inadmissible the employment of edge-rails or turned-up tram-plates are on the public roads, the same objection or difficulty of travelling does not apply to the " scantlings of iron " employed at Colebrook-dale ; on which point we shall hereafter have some remarks to make.
The introduction of metallic surfaces to the wooden rails was, however, at first productive of serious evils ; for the resistance or adhesion to the surface in descending inclined planes was thereby so much reduced, that the ordinary brake was found to be quite ineffective in counteracting the force of gravity. Recourse was therefore had to the double or self-acting inclined planes, by which the surplus force of gravity of the load descending one plane was employed to drag up the empty waggons on the ascending plane. At this period of time the steam-engine was employed in raising mineral from the pits by means of ropes coiled round barrels; the application, therefore, of a similar process to the raising of a train of loaded waggons up an inclined plane became obvious, and was extensively adopted in the north of England.
The introduction of cast-iron plates, having an upright ledge, was originally effected by Mr. Carr, at the Sheffield colliery, about the year 1776. These were at first called plate-rails, but are now usually distinguished by the term tram-plates, from the circumstance of their being used for trams or waggons to roll upon. The form of these, as used in the under-ground colliery at Sheffield, belonging to the duke of Norfolk, is delineated in the following figures. Fig. 1 being a plan, and Fig. 2 a transverse section of Fig. 1, through the dotted line a b; c c are the plates, 6 feet long, of the sectional shape shown at c c, Fig. 2; at each end of the rails holes were cast, through which stout nails were driven into the sleepers d d d, made of wood, in the first instance, and afterwards of blocks of stone, by Barnes, Outram, and others.
In many of the railroads where horse-power is employed to draw the car riages, the animal is frequently required to check the velocity of the waggons, so that they may not exceed a certain degree of motion ; and when a horse is pressed beyond his power of resistance, he necessarily quickens his pace ; if, under these circumstances, he makes a trip, he is almost sure to fall, and then to suffer severe, if not fatal injury, by being forced down the declivity. To prevent such serious accidents, Mr. Le Caen, of Llanelly, in Caermartliensbire, about thirty years ago, constructed a brake of great simplicity, which cannot fail of checking or stopping the carriages under such circumstances, and is therefore deserving of more public notice than it has hitherto received. In the following engraving we have shown the application of this contrivance to a common Welch cart used upon rails. a represents the brake, which we have shown as made of iron, it being in the original a very clumsy mass of wood, shod with iron; the shoe or skid ought to be somewhat broader than the tire of the wheels ; the top of the brake turns upon a pivot at b, and the lower part is connected by a strong chain o to the shaft d. The shafts are jointed at e to the frame of the cart or waggon ; and when the horse is upon his legs, the shaft-chain and brake are in the several positions shown by the dotted lines at/g h, the latter, which repre sents the brake, being then quite clear of the wheels es well as the rails ; but when the horse falls the shaft takes the inclined position shown at d, and the skid of the brake a, by its weight, is thrown under the wheel, which it takes off the rail; the rolling motion is thus changed into a sliding one, and the great friction thus induced either stops the descent of the carriage, or retards it suf ficiently to prevent serious injury resulting. In a letter to the Society of Arts,
in London, Mr. Le Caen observes:—." To prevent the'greet trouble arising from turning a waggon round upon s railroad, it would be better to have a brake to each of the four wheels; in which case, after the waggon has discharged its load at the place of destination, the chains c may be loosened from the shafts, and fastened upon hooks so as to keep the brakes suspended over the road; the bolt at e which attaches the shafts to the body of the waggon, is then to be removed, and, with the shafts, placed in a similar manner on to the other end of the waggon, which now becomes the fore part, the horse drawing it back to be again loaded. Whenever the waggon is ascending, the checks behind the waggon may occasionally be let down and used as rests to relieve the horse when necessary. ' In the construction of all surface railways, the first object considered is the direction of the road, which, in all cues, should be so formed, and with such declivity as may be best calculated not only to suit the nature of the ground through a hich it passes, but also the trade to be carried on upon it. If, for example, as frequently happens to be the case, nearly the whole traffic of a country is in one direction, the road should then obviously decline that way, so that the waggons and their contents may descend on this inclined plane as much as possible by their own gravity. But in all cues particular attention ought to be paid to the extent of the trade upon the railway, so that the inclination may be as nearly as possible proportioned thereto, consequently, the draught each way equalized; and in cases where the transit of merchandise to and fro should be nearly equal, it would be most beneficial to have the railway level : but it sometimes may happen that the nature of the ground is such as not to permit that declivity or level best suited to the trade ; the line should, in that case, be varied, and, if possible, the inequalities made up an as to bring it as near as possible to the proper standard, if it can be done at any moderate expense; but when the inequalities happen to be such as to render this impracticable, the only resource to be found is in inclined planes. For example, where the differences of level between the two extremities of road are such as would render an.equal declivity too steep, then the road must be carried either on a level, or with the due degree of slope as far as practicable, and then lowered by an inclined plane, on which the waggons are gently let down by a brake, and dragged up by an additional power to that which is made use of for drawing them along the road. But in the laying out and formation of all railways, much depend. upon the skill and judgment of the engineer, as it is quite impossible to lay down any general plan to suit all cases ; for, it must be recollected, every situation presents some peculiar circumstances. When once the line of railway is fully determined upon, the next step is to form the road, which requires much attention ; it must be of sufficient width to contain the opposite rails, and for forming a footpath on one side. There is no prescribed distance between the rails, as, in some cases,preference is given to long narrow waggons, and in others, to thole of a broad short shape; consequently, the distance the rails varies from three to four and a half feet; hence from nine to twelve feet has been usually apportioned for a single road, and from fifteen to twenty for a double one.