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Parliamentary Estimate.—An estimate of the probable cost of the proposed railway has to be made out in a form prescribed by the Board of Trade. This estimate must state the quantities and cost of the various items; cuttings, embankments, bridges, accommodation works, viaducts, culverts and drains, metalling of roads, permanent way and fencing, sidings, junctions, stations, contingencies, land and buildings, &c.
Board of Trade Regulations for Light Railways.Of late years, in order to avoid the expensive procedure necessary to get a Bill passed by Parliament authorising the construction of a railway, the Light Railways Act has been passed, and the Board of Trade in September 1896 issued their "Rules with respect to applications to the Light Railway Commissioners for orders authorising Light Railways." The engineer should provide himself with a copy of the latest rules, which may be had on application.
Under the Light Railways Act it is not necessary to go to Parliament for sanction to construct a railway if it is made to come under the regulations of the Light Railways Act which chiefly affect the signalling and working of the line. The scheme is considered by the Light Railway Commissioners, at an inquiry held locally, at which the engineer must attend and give evidence. If sanctioned by them, it is then passed on to the Board of Trade for final approval. As far as the engineer or surveyor is concerned, his work is much the same whether the line is an ordinary railway or a light railway.*
Example of Parliamentary Plan and Section of Railway taken from actual practice.-Figs. 167, 168, Plate VIII., are examples of the Parliamentary plan and section of a railway actually constructed and surveyed as already described in this chapter.
Working Surveys.-The Bill having been passed, or the sanction of the Light Railway Commissioners and Board of Trade having been obtained, the engineer is forthwith (let us hope) instructed by the promoters to proceed with the detailed or working
A copy of the Parliamentary Regulations for Ordinary Railways should be obtained, which may also be had on application.
dnance bench mark on the Bell Inn, at point marked X on plan
[To face p. 224.
Revising and Improving Parliamentary Location.The working survey is usually conducted on the 25 in. Ordnance scale, on the sheets of which the Parliamentary line and the limits of deviation should now be pencilled. A careful examination of the Parliamentary section and plan and a comparison of the ground with the larger 25 in. scale map will usually result in various modifications of the line presenting themselves, by means of which cuttings and embankments may be reduced.
As a rule, it will be possible to decide definitely upon these merely by inspection of the ground, but in difficult country it may be necessary to take levels and cross sections and plot one or more longitudinal sections of the proposed alterations before fixing upon the final line.
Final Location of Line in Difficult Country.—The ruling gradient and minimum radius of curve have of course been already fixed on the Parliamentary survey and plans, and the method of locating the line in difficult country is as follows:Take levels over the Parliamentary line laid down on the map and leave marks where cross sections are to be taken. The points where cross sections are to be taken will be determined by the general configuration of the ground. They should be such that the surface between adjacent cross sections is approximately plane, or roughly speaking, cross sections should be taken wherever the slope of the ground changes. For methods of cross sectioning see Chapter III. As a rule, the clinometer is the most rapid to take cross sections with. Having taken and plotted the cross sections as shown in Fig. 169, the contours are to be taken off them and laid down on the plan as follows:-Draw a vertical AB to represent the centre line of the railway as laid down on the map. Suppose the reduced level of the surface of the ground at the centre line of the railway is 102.80, and that contours are required 5 ft. apart vertically. Then the first contour above the centre line of the railway will be the 105 ft. contour, i.e., the contour whose reduced level is 105.00 and 105.00 102.80 2.20. Plot up, therefore, 2.20 ft., and ab, bc, cd, each equal to 5 ft. Similarly the first contour below the centre line of the railway will be the 100 ft. contour and 102.80. 100.00 2.80. Plot down, therefore, 2.80 ft., and ef, fg, gh, each = 5 ft. The points h, g, f, e, a, b, c, d, will then be at the reduced levels 85.00, 90.00, 95.00,
100.00, 105.00, 110.00, 115.00, 120.00 ft. respectively, and the horizontal lines hs, gr, fq, ep, ak, bl, cm, dn, will give the horizontal distances from the centre line of the railway to the 85, 90, 95, &c., contours. These horizontal distances are to be measured off the centre line of the railway on the plan, and will give the position of the contours at that point.
Each cross section is similarly treated, and the positions of the contours plotted on the plan. By joining these corresponding points on the plan we then get the contours of the surface of the ground. A quicker method is given in Chapter III., graphic interpolation of contours, page 154.
Fig. 169.-Position of Contours from Cross Section.
If the scale of the general plan is too small to plot contours 5 ft. apart vertically, the centre line of that portion of the railway to be cross sectioned and contoured should be laid down on a larger scale on a separate sheet and the contours plotted on it.
Having then decided on a trial gradient, calculate the distance in which the rise or fall of the gradient is 5 ft. if the contours are 5 ft. apart vertically; if 10 ft. apart, the distance for a rise or fall of 10 ft. Take now this distance in the compasses, and step from contour to contour, marking the points where the compass touches each contour. A line joining these points is then the line on which there is neither cutting nor bank, and is called a "surface line." The proper location of the railway is then the line which can be