the contracts of the principal works in the intermediate portion are completed. It is expected that the line will be completed from London to Maidenhead in the Autumn of 1837, from Bristol to Bath in the Spring of 1838, from Maidenhead to Reading and to Oxford by the Autumn of 1838, to the Cheltenham branch in the Spring of 1839, and the whole completed within four years of the commencement. The satisfactory execution and completion of all the contracts in their different stages, within the respective times allotted to each, is secured by periodical penalties. Length 5. General Dimensions. Breadth of way on embankments and viaducts, and under bridges Viz. for double line of railway guage, or width of each 7 feet Space between the two lines Space outside ditto, 5 feet each Breadth in cuttings (additional space for drainage) Cuttings-general run of the deep cuttings Height to crown of arch Planes-greatest inclination 1 in 106, or 50 Sum of level planes, or not exceed- Total length 6. Estimates. 117 miles. 30 feet. 14 6 10 30 feet. 36 to 40 feet. 30 to 40 feet. feet per mile. miles fur. 3 7 113 5 117 4 Cost (as proved before Parliament). For making the railway (at full prices for Traffic. Annual passengers, 522,184, (persons now travelling various distances on the line, exclusive of short journeys within 15 miles of London,) at 2d. per head per mile Werchandize, cattle, and parcels Deduct expenses (on scale of Liverpool. 337,579 6 8 Net revenue £347,008 11 0 Or, 137. 17s. per cent upon a capital of 2,500,000Z. 7. Table of Distances, Gradients, and Levels. 8. Table of Time, which will be occupied in travelling between London and Bristol, and the principal towns on or near to the railway, at the minimum velocity of 25 miles per hour. Chippenham 3 45 4 0 Melksham, by a branch of 5 miles Trowbridge, or Bradford, by a branch of 9 miles 4 15 Bath Bristol 4 10 4.40 ON THE LAYING OUT OF LINES OF RAILWAY. BY THE EDITOR. [Continued from No. II., page 59.] I was unfortunately prevented at the time from concluding the few remarks I had then to make on laying out lines of railways from circumstances over which I had no control, and since that time I have been unable to resume the train of thought I was then in, and consequently most of my remaining views have been lost, some of which appeared to me to be important. However, as it is necessary to conclude the subject in the present volume, I shall here add a few remarks; and should I ever recollect what I have at present lost sight of, I will throw them together in the form of an appendix. 10. Railways in the immediate neighbourhood of large towns should always be carried on an embankment or viaduct, or if necessitated to go into cutting, they should be well protected with lofty walls. This is a matter of such obvious necessity as scarcely to require an observation. If near a large town a line of railway was left exposed, where would be the possibility of preventing accidents? It matters but little whether it was left without fence or exposed in a cutting so that the idle and mischievous might be able to throw sticks or stones down on it. As to keeping them off, it would be akin to impossibility and a stick or stone thrown on the rails by some idle fellow might upset a train or turn it off, and produce the most disastrous accidents. Prudence would tell us, wherever it is possible, to carry it along a lofty embankment or viaduct. Such a method would afford the greatest safety to the train, and most convenience for crossing it by the inhabitants. But if this cannot be, it is indispensable to guard it well with high walls. 11. In long lines it seems better to concentrate the gradients in one or two places than to have a series of undulations or planes up and down which full steam cannot be applied. Great diversity of opinion exists on this subject. Our reasons are simple and few. No line works so economically and well as a perfectly level line; that, therefore, which approaches the nearest to it must obviously be better than one which approaches less. A line which is perfectly level can carry a greater load with the same expense than any other. For though it be true, as I have before shown, p. 206, that a line up and down whose inclines full steam can be applied, can be traversed in precisely the same time, setting aside the resistance of the atmosphere, as one in which the inclination is either nothing or uniform throughout, yet the inclines, generally speaking, must severally be sharper than than that of a uniform plane. Therefore, and because it is the most difficult plane on the line that determines the load which can be carried throughout, the undulating line must evidently be less powerful than the non-undulating. Again, with the same load the undulating line in actual practice could not be traversed in the same time. For the resistance of the atmosphere varying in the duplicate ratio of the velocity, is much more increased in the descent than it is diminished in the ascent. Nor does the shorter time in which it acts in descents make up for the great excess of its action in them. In fact the total time of transit appears not only to be greater, but the mean strain, and consequently the wear and tear, greater in an undulating line than in one that does not undulate. If this then is true for a given length up and down easy planes, in which full steam can be applied, how much more so is it if the inclines exceed those, and where in every descent the power of the engine is wasted, and the steam sent off to buffet the atmosphere without any useful return ? In traversing an undulating line there are two distinct species of loss-the loss of load in ascending planes so much steeper than are needed, and the waste of power in descending such planes as are too steep for the application of full steam. What the descents are which admit of full steam is a matter which is not exactly agreed on. It must depend on considerations of safety and of the load to be carried. Full steam may evidently be used with heavy loads down much steeper inclines than it can with light. For example, suppose we have a load which the engine will take along 30 miles an hour on a level, and let it be considered unsafe to go down any plane quicker than 40 miles an hour, this would correspond to a fall of 47 feet per mile by our table p. 95. Now, if the load was doubled the velocity in every case would be halved, and the 40 miles an hour would require a plane falling between 11 and 12 feet per mile; that is, a double load could travel with as much safety down descents of 11 ft. a mile as the other down those of only 4.7 ft. Some may imagine that to be equally safe a heavier load should go with a less velocity. This, however, is not the case. The danger is not supposed to arise from the breakings of the carriages or of the rails-for if they are not made of two or three times the strength they are wanted they ought not to be used-but from the trains running off the rails. In this respect heavy loads, by keeping the trains tighter on the rails, are manifestly much less likely to be thrown off than light, and therefore would retain equal safety at higher speeds. As far as regards the actual expenditure of power, it does not appear that there is any difference if full steam can be used all the way, and the atmosphere be disregarded, whether the line undulates, or is level for a certain extent, and then all the ascents united into one steep plane. In each case the expenditure of power is the same. But the advantage of concentration is, that all the great efforts, instead of being scattered over a vast extent of ground, are brought to bear upon one point, for which provision is always made. Besides it is much better and more comfortable for the passengers to have a change of velocity for a short distance, and then to prosecute their journey by one steady uniform pace, than to be creeping along sometimes 4, 5, or 6 miles an hour, and at others shaking their nerves with the terrific |