now no standard of width whatever, in any of the railway bills, which pass the legislature; and it is, therefore, left to the discretion of the railway companies, or their engineer, of what width the railway shall be constructed. The Great Western railway has been made seven feet wide, between the rails, by the engineer, Mr. Brunel, jun. ; and the railways recently constructed, and now in operation, in Scotland, are five feet six inches wide; some of the old railways being four feet six inches. It is impossible to conceive the confusion, which may be the result of this departure, of the legislature, from a standard width for all railways; especially if railway companies, and engineers, follow the dictates of their own opinion, without reference to the general convenience of the public. The delay, expense, and inconvenience, of changing from a line of railway, of one width, to another of a different width, where despatch, and rapidity of travelling, is the great characteristic of the system, must be inconceivable. It is due to the public, that a full and comprehensive enquiry should be instituted, by the legislature, to determine the proper width, now to be adopted; not only with reference to all railways to be made in future, but, likewise, with reference to those already made and when a conclusion is come to, and the best width, under all the circumstances, determined upon, it should be made a standard, in all railway bills, and should not be allowed to be departed from, under any pretence whatever.

;

Without presuming to determine upon so important a question, on which there is a great difference of opinion, amongst engineers; we shall, for the present, assume the width between the rails to be four feet eight inches and a half. The breadth, of the bearing part of the rails cannot vary much; about two inches

and a half, seem to be the width agreed upon by almost, if not all, the engineers of the different lines. of railway in England. The width between the outside of the rails will, therefore, be five feet one inch and a half; or five feet one inch, if the breadth of the rail itself, be two inches and a quarter.

same.

5.-Width between the Two Lines.

The next consideration is, the width between the two lines of railway. Upon the Liverpool and Manchester, the width was made the same as that between the rails, viz., four feet eight inches and a half. On the Newcastle and Carlisle railway, it is made the On the London and Birmingham railway, and the Grand Junction railway, the width is six feet; the latter width seems, certainly, preferable, upon great lines of railway; but experience has shewn, that no great inconvenience is felt upon lines of the lesser width. In the drawings of Plate V. the width is six feet.

§ 6.-Width on the Outside of the Rails.

The next question to determine is, the width required on the outside of the rails, or between the rails and the edge of the embankment, or side of the excavations. This is, to a great extent, determined, by what is necessary to keep the blocks firm, to preserve the stability of the rails, and to effect the passage of the engines and carriages along the railway with every possible security. On private railways, and upon some of the public railways, where economy of construction has been a primary object, a width of three feet and a half, from the rails to the outer edge of the embankments, or footpath, of the excavation, or from n to k,

or o' to l, in Figs. 2 and 4, has been found sufficient to secure adequate firmness and stability to the blocks and rails; four feet, in any case, we should deem quite sufficient, to effectually accomplish these objects, viz., the stability of the blocks and rails.

But there is another very important object to effect, the width necessary to secure the safety of the engines, and carriages, passing along the railway; and which is more difficult to determine, without going into the subject, in a speculative point of view. If we were to appeal to the experience upon the Liverpool and Manchester railway, and upon the Newcastle and Carlisle railway, where the radius of the curves, upon the latter, is less than will, in all probability, be made upon any of the railways now in formation; (that railway having been laid out before locomotive engines arrived at the perfection they have now attained, and with a view of using horses upon it,) we should say, that four feet is quite sufficient, to secure the safety of the passengers and goods.

On approaching a narrow embankment, at a rapid rate, the general impression is, that the engine will run over the side of the embankment, and drag the train of carriages over it. Nothing can be more fallacious, for, if the engine was, by any accident, to run off the rails, it would not drag the carriages after it. If it goes over at all, the carriages will push the engine, but the engine will not drag the carriages over, for this very simple reason; if the engine does run, or is thrown off the rails, a diminution of its speed immediately takes place; and, there being no such check to the carriages, their inertia carries them forward against the engine, pushing it on until the whole train is stopped. In approaching the question, we must, therefore, consider it with reference to that mode of action; and, likewise, with

reference to the immense tangential force, inherent in an engine and train of carriages, moving at so rapid

a rate.

Supposing an engine thrown off the rails, the wheels have then to run upon the loose coating of the road, the resistance of which, to the wheels, is very great, and which we may safely state as being equal to one fifteenth of the weight. The distance the train will run, before stopping, after being thrown off the rails, will, therefore, depend upon the resistance, and the velocity with which it was moving, when thrown off the rails.

The formula, s

v2

64 P

will shew the space, s, in feet, the train will pass over before stopping, v being the velocity in feet, per second, which the train was moving at, and p the resistance to the wheels, which we have called one fifteenth of the weight. An engine and train, therefore, travelling at the rate of twenty miles an hour, and being thrown off the rails, will run about 210 feet, or seventy yards, before stopping; but if the same train is running at the rate of twelve miles an hour, it will become at rest in about seventy-six feet, or twentyfive yards.

Upon a straight line, the tangential force will cause the train to keep along the line of the road, and there will not be any great danger of its being diverged four feet in 210 feet, supposing four feet to be the width, on the outside, between the rail and the edge of the embankment. But in a curve it is different, the direction of the tangent then tending to cause the train to run towards the side of the embankment. It will, in this case, therefore, depend upon the radius of the curve, what distance the train would run before reaching the side of the embankment; and whether it would reach the side within the distance of 210 feet, or

seventy yards, in the one case, or seventy-six feet in the other.

The versed sine a F, of a curve, the radius of which is represented by c E, and the sine by E F, is a FC E -CE2-E F2. On curves, the radius of which is 1200, 1800, and 2400 feet, the versed sine, or distance of the tangent from the curve, in 210 feet, will be eighteen, twelve, and nine feet respectively; which would be the position of the train, if, when moving at the rate of twenty miles an hour, it was projected from the curve in a straight line. But if the train was moving at the rate of twelve miles an hour, seventysix feet being the length it will run before stopping, or of the tangent, the distance from the rail on the curve of the shortest radius, or 1200 feet, will only be about two feet and a half.

We see, therefore, that three and a half, or four feet breadth on the outside of the rails, which appears to be sufficient to keep the blocks firm, is likewise sufficient to prevent all risk of the trains running over the side of the embankment, when the velocity is kept below twelve miles an hour, and the curves of not less a radius than 1200 feet; but, that, when the velocity is increased to twenty miles an hour, if no other obstacle occurs to prevent the train from running over the embankment, than the mere resistance of the wheels, upon the coating of the road, four feet on the outside of the rails are not sufficient. There are, however, other safeguards, which operate to change the direction of the trains, from the tangential course they would otherwise pursue, and divert them to that of the line of the road, or of the rails. A small depth only of road material being spread above the top of the blocks, when a train is thrown off the road, and