§ 11.-Coating the Railway, or, forming and draining the Foundation for the Blocks.

We now come to a most important part of the construction of railways, viz., forming a foundation for the blocks, and laying down the rails. The line having been formed to the proposed inclination longitudinally, it is then levelled transversely, or a little convex, with a rise of three or four inches in the middle, so that the water may fall towards the ditches on each side. But, as the material constituting the base of the railway, in the excavations, and embankments, will, in a general way, be gravel, clay, or other earth, which would retain the water, and which the blocks would sink into when subjected to the action of the carriages upon them; it is necessary to cover these surfaces over with some material, which will allow the water to drain off from the bottom of the blocks, and which will likewise form a sufficiently firm foundation for the blocks to rest upon. This is generally done by a layer or coating of sandstone, or other stone, broken into small pieces, and spread upon the line of formation of the railway. 1, 2, Figs. 2 and 3, or a a, Fig. 12, shew this layer of stone, with the blocks resting upon it. This broken stone, therefore, serves as well for a firm foundation for the blocks, as for a drain to carry off the water. The thickness of coating, or broken stone, laid on, is generally nine to twelve inches, the stones not being larger than will pass through a ring two and a half inches in diameter; but when the blocks are set upon this as a foundation, a little sand, or stone broken extremely small, is put upon the larger sized coating, to make the block bear more firmly. When the railway is laid down, it is then filled up between the blocks, and on each side, to the level of about three inches above the top of the blocks;

with small gravel, sand, marl, or any material of that kind, which will consolidate sufficiently hard, around the blocks, to keep them steady and firm. In some cases, the under coating is not spread across the whole width of the formation, but only sufficiently wide to act as a support and drain to the blocks, the remainder of the width being filled up with gravel or sand.

Where good sandstone coating can be obtained, nine to twelve inches are found quite sufficient, generally, to keep the blocks and road effectually free from water; but, where good coating cannot be obtained, or where the width of the road is very great, it is, therefore, necessary to have recourse to a different mode of drainage. In these cases, a stone, or brick drain, is carried along the middle of the line; with similar cross drains running from it into the side ditches, at certain intervals. Figs. 4 and 5 will shew the manner in which this is done. Fig. 4 being the plan, and Fig. 5 an elevation, a b, are the centre drains; and ef, ef, the cross drains, running from the centre drain into the side ditches, cd, c d. These drains may either be made with bricks or stone, as may be found most economical, the dimensions varying from four to six inches square. Similar drains are formed on the embankments, the side drains, in this case, running down the slopes, to carry off the water to the side ditches. The necessity for these drains depends, however, much upon the nature of the subsoil of the excavations, and the material forming the embankments.

§ 12.-Setting the Blocks.

The drainage having been effected, and the under coating having been all spread upon the line, the next operation is, setting the blocks.

On all the excavations where stone blocks can be had at a moderate cost, and on the embankments which are

sufficiently consolidated, stone blocks are, decidedly, the best support for the rails; but, upon high embankments made of clay, and which are constantly settling down, it is found most advisable, in the first instance, to lay down wooden sleepers, stretched across from one rail to the other. Figs. 3 and 4 exhibit both modes; A B represent stone blocks; and c D, wooden sleepers. The stone blocks now laid down are never less than two feet square, by one foot thick; and they are generally laid down diagonally, as shewn in Fig. 4. The reason for laying them thus, is, that they act with greater effect transversely, in steadying the rails; and the workmen can have access to all the four sides, to put the block right in case of displacement, which cannot so well be done, when the blocks are laid at right angles to the line of road. Setting the blocks is of great importance, as upon its being well done, depends the permanent stability of the road. The old method was, after having spread the bottom of the excavation, or top of the embankment, over with a layer of ashes, or small stones, or gravel, to place the blocks upon this, with the chairs and rails attached to them; workmen were then employed to push the ashes, or sand, underneath the blocks, with narrow shovels, at the same time beating upon the upper side of the blocks with heavy mallets, until the rails were at the proper level. In this manner of setting the blocks, it will be seen, that no firmer seat, or greater solidity could be given to the foundation, than what was effected by the blows of the mallets upon the blocks; which having little effect in compressing or consolidating the foundation, when the carriages came to run upon the rails, the blocks immediately sunk down, and it required the workmen to be constantly pushing ashes or sand underneath, to raise them to their proper level, until they came to a permanent seat; or, in fact, until

the seats of the blocks became sufficiently firm to resist the weight of the carriages passing over them, or until the carriages had no effect in depressing the blocks.

In laying down the Liverpool and Manchester railway, Mr. Stephenson adopted a plan, by which, in setting the blocks, the foundation was, in the first instance, compressed and consolidated to such an extent, that the weight of the carriages had no effect in causing the blocks to yield. This was done by the impact of the blocks themselves, the principle being, in setting the blocks, to employ a force, weight, or impact, upon the foundation whereon they were to rest, greater than the weight or effect imposed by the action of the carriages upon that foundation; and, consequently, the latter could have no effect in further compressing the foundation, and causing it to yield, or be depressed. To effect this, he made use of the block itself, by successively lifting it up, and allowing it to fall upon the seat, whereon it was intended permanently to rest. The block was raised by every operation to such a height, as that the impact or blow upon the coating or foundation, when let fall, was much greater in effect than the direct weight or pressure of the carriages.

This system of setting is, however, entirely subverted, if the foundation, whereon the coating is laid, be not perfectly firm and solid. The least subsiding or sinking of the foundation, renders all this care, of effecting a firm seat for the blocks, useless. Upon excavations well drained, it may be adopted with complete effect; and if well done, and if the blocks are sufficiently large, they require very little care in keeping right afterwards. Upon well consolidated embankments also, this plan of setting can be practised with like effect; but in yielding embankments, made of clay, and before they become

perfectly consolidated, the whole expense of thus setting the blocks is rendered useless by the least yielding, which destroys the foundation, which so much care and expence have been bestowed to form.

The mode which Mr. Stephenson used for thus setting the blocks, is as follows; and the same plan is now practised in setting the blocks, upon all the modern railways. A lever, about twenty feet long, is fixed upon a portable stand, the lever being sufficiently strong to lift one of the blocks, but otherwise very flexible; the stand is about five feet high, the fulcrum of the lever being placed at such a distance from one end, that a man can readily lift one of the blocks. A chain fixed to the short end of the lever is fastened to the chair of the block; it is thus lifted or jerked up, about a foot high, and then let fall upon the coating, and this is repeated a great many times; another man, at the same time, throwing underneath the block, sand, or fine gravel, until the successive blows effect a solid and firm foundation, and the block is firmly seated upon the coating of the road. At each of the times when the block falls, the attendant, by proper squares and sights, causes it to fall on the proper place, and, at last, to be firmly seated; not only level transversely, but, also, correctly ranging, with the longitudinal level, or general inclination of the road.

In this manner, the blocks are all set, along the whole line of road, or along certain lengths, before the rails are keyed to the chair; but the blocks, being set perfectly parallel with the general inclination of the road, and properly level transversely, and the chairs being all of the same height, when the rails are keyed down, they, of course, form a perfectly correct line of road. It need scarcely be added, that, when the blocks are once seated, they should not, on any account