the wheels have to run upon this material, they sink into it, and meet with the blocks, which act very powerfully in stopping the trains, or of keeping them in the direction of the road. Should, however, the wheels overtop the blocks, they then meet with the rails, which presents an obstacle, standing at least five or six inches above the surface of the road; which the momentum of the train cannot raise the wheels over, and which effectually prevents it from running any further out of the line of direction of the road. If, therefore, the width on the outside of the rails be such, as that, when the wheels on one side of the carriages are within the line of the rails, the opposite wheels do not reach beyond that width, or to the edge of the embankment, the train cannot by possibility run over the embankment. We, consequently, come to this conclusion, that, where the speed is not greater than twelve miles an hour, and the radius of the curves not less than 400 yards, a width of three and a half or four feet on the outside of the rails, or from n to k, or o' to l, is sufficient; but that, when the speed is increased to twenty miles an hour, or upwards, the width should, at least, be equal to the distance between the rails of the railway.

Upon the London and Birmingham; and the Grand Junction, the width on the outside of the rails is five feet, the distance between the rails being four feet eight inches and a half. On some of the railways, a mound of earth, shewn by the dotted lines at i k, lm, Fig. 3, is raised about two feet high above the level of the road upon the embankment; which acts as an additional, and, we should say, an effectual, security against any danger that can possibly arise, from the trains being thrown over an embankment.

We have gone into this part of the subject rather fully, it being very desirable, in an economical point of view, in the construction of railways, that no greater width should be taken, than what is, absolutely, necessary; at the same time, the safety of the passengers requires, that the width should be such, as to effectually guard, so far as human care can, against any accident.

Supposing the width, between the outside of the rails, to be five feet one inch; between the two lines, six feet; and the breadth on the outside of the rails, five feet on each side; we have, then, the width of the entire road, at the level of the rails, or, between k and l, Figs. 2 and 3, Plate V., twenty-six feet two inches. The only remaining questions for consideration, are the slopes, gk, hl, required for the filling of the road, and the width required for the drainage of the excavations. The depth of the filling is two feet, or two feet three inches, and a slope of one foot horizontal, to one foot perpendicular, is found to be sufficient; although, in some cases, on the embankments, it is made the same slope as that of the embankment, which would be, for the two slopes, i k, lm, four feet six inches, in the former case; and six feet nine inches, where the slopes are one and a half to one; or nine feet, where the slopes

are two to one.

The width of the drainage, c g, hd, Fig. 2, will vary, according to the quantity of water required to be conveyed off; but one foot and a half on each side, at the formation level, is generally found sufficient.

§7.-Width of Excavations.

We have, then, the width of the excavations at the formation level, as follows:

Two lines of railway, including rails,
Width between the two lines,

Do. on the outside of rails,

Do. required for the slopes,

Do. for the drainage,

10 ft. 2 in.

6

which will be the width, fi, cd, Fig. 2, Plate V.

§ 8.-Width of Embankments.

And for the embankments, or g h, Fig. 3, which require no width for drainage, three feet less, or thirty feet two inches. Where mounds are raised on the embankments, as shewn by the dotted lines in Fig. 3, the width, ik, lm, is two feet on each side, requiring thirtyfour feet two inches, where the slope of the filling is one to one; or, thirty-six feet, where the slope is one and a half to one; and thirty-eight feet, where the slope is two to one. The mode of calculating the quantity of earth contained in any cutting, or embankment, has been published: and tables constructed by Mr. Bidder; more elaborate tables have likewise been made the subject of a publication, by Mr. Macniel.

The filling of the Grand Junction railway, is two feet three inches; and on that line, where the slope of the embankments is one and a half to one, the width, at the formation level, is thirty-seven feet; and, where two to one, thirty-nine feet four inches.

§ 9.-Slopes of the Excavations, and Embankments. Having now ascertained the width, at the formation level, it is next necessary to determine the angle to be given to the slopes, ss, of the excavations and embankments. These depend, in some degree, upon the depth of the excavation, or height of the embankment; in the former, when the material is sand, gravel, chalk, or gravelly clay, a slope of one and a half horizontal, to one perpendicular, is quite sufficient; and in excavations, up to thirty or forty feet, this slope has been found to stand very well. In some descriptions of clay, such as the plastic clay of London, and clay of a similar nature, a slope of one and three-fourths, or two to one, is necessary. In all the excavations on the Newcastle and Carlisle railway, through a district sixty-two miles in length, the slopes are made one and a half to one, and they have been found to stand quite well. The sand cutting through the Cowran Hills, on that line, is 110 feet deep, and it is interspersed, in some places, with thin layers of clay, and, yet, it has stood quite firm, with a slope of one and a half to one. The embankments are generally made, with the same slope, as that of the excavations; and it is presumed, that, with whatever slope the excavation will stand, the embankment formed of the material from such excavation will require, but will stand with the same angle of slope, as that of the

excavation.

On all the modern railways, the slopes are covered with a layer of soil, which is procured from the base of the embankments, or from the top of the cuttings; this layer of soil is spread over the face of the slope about six inches thick, or of the thickness which the soil from those places will yield. It is of great importance to the

security of the slopes, that the soil should be laid on as soon as possible, after the excavation is made, or the embankment consolidated; and sown with grass or clover, or both, to get a turf upon it before the slopes are affected by the action of the weather. By doing so, slopes will often stand, where, without the soiling and turf, or when exposed to the action of the weather, they will not stand; ss, in Figs. 2 and 3, shew the soil laid upon the face of the slope.

In these drawings, we have shewn the slope of the excavation to run down to the formation level or bottom of the drain. In some cases, where stone is plentiful, and where there is an excess of cutting, side walls, similar to ef, Fig. 15, are built, to retain the sides of the excavation, the dotted line, p q shewing, in that case, the line of the slope. In such cases, stone drains, similar to that shewn at g, are made to still further diminish the width of the railway. The propriety of doing this is, however, entirely a matter of calculation.

§ 10.-Fencing the Railway.

rqp, and p'q'r', Figs. 2 and 3, shew the mode, generally practised, of fencing the railway. The ditches, rq, rq, are mostly made four feet wide at top, and one foot and a half wide at bottom, and of such a depth as will carry off the water; and the mound, pq, p' q, about the same section, and about two feet high, being formed from the excavation of the ditch.

The ditches, rq, r'q', are, of course, intended to carry off all the water, and effect the drainage of the adjacent lands; the ditches, c g, hd, Fig. 2, being to carry off all the water which falls, or is brought into the excavation, or line of railway.