Railway Construction. William Hemingway Mills
gradients, the greater the cost and time in working the traffic, and if there is every probability of early and large development, the prospective increase may warrant an additional outlay in the original construction.
Large, open plains and wide valleys of important rivers generally afford ample latitude for the selection of a suitable route, and, by taking advantage of the gradations of altitude, a favourable course may be adopted without incurring excessive gradients. When traversing moderately hilly districts, some low ridge or opening may be found, which may form a pass from the one side to the other, and the line may be laid out for a long distance to lead gradually up to the highest point. But when a route has to be laid out over some of those lofty mountain ranges which are met with abroad, the locating of a suitable line, or of any line, becomes particularly intricate and difficult. A comparatively low ridge may be found possessing features in favour of the project, but the question will be how to reach that point. The nearer the summit of these high mountains, the more precipitous the sides; no one slope can be found sufficiently long and uniform to permit a practical direct ascent, and the only way out of the difficulty is to make a series of detours along the various spurs of the mountains to gain length to overcome the height. Each detour has to be the subject of most careful study. Forming part of a long series of ascending gradients, it has to follow the winding of the mountain-side, must be laid out to be always gaining in height, and will comprise important works, many of them of considerable extent, necessary for protection against the floods and atmospherical changes of the locality.
In these higher altitudes nature is met with on the grandest and most rugged scale. Deep gorges, wide ravines, and almost perpendicular rocks form the pathway along which the line must be carried, and the skill of the engineer is taxed to the utmost to select a course which shall comprise a minimum of the works of magnitude. Mile after mile of line must be laid out in almost inaccessible places, loose or broken rocks must be avoided, a firm foundation must be obtained at all points skirting high ledges, and ample provision must be made for those mountain torrents which rise so suddenly, and are liable to sweep away all before them.
Many grand examples of these detour lines are in existence in different parts of the world, and the traveller passing over them can realize the difficulties that had to be encountered, and the masterly manner in which they have been overcome.
Before proceeding to carry out the works of any line of railway, it is necessary to prepare a complete plan and section of the line, showing the route to be followed and the position of the various curves, gradients, and principal works. Within certain limits, the course of the line may have to be slightly modified as the work proceeds, in consequence of ground turning out unfavourable, river-crossings treacherous, or of sites involving so many contingent alterations that it is found better to avoid them altogether. The route should, however, be so carefully studied out before completing the final plan and section, as to leave only minor deviations of line and level to be dealt with in the actual carrying out of the work.
The promoters of lines in the United Kingdom obtain valuable assistance from the ordnance maps, which give full and reliable information regarding the position of all roads, rivers, and boundaries of counties, parishes, and townlands. In many parts abroad local maps are scarce, and not always accurate, and engineers have to depend principally on their own surveys, and rely upon the resident local authorities for any particulars as to divisions of territory. On some of our great colonial plains, and out in the far west of America, a line may be laid out for miles without a single landmark to localize it on a plan; but careful setting out, and the relative levels of the ground and gradients, as shown on the section, will always indicate the correct position of any portion of the work.
Both at home and abroad complete plans and sections of any proposed railway must be deposited with the proper Government authorities, and must be approved and sanctioned by them before permission can be obtained to proceed with the works.
The regulations regarding the scale and general arrangement of these plans and sections vary in different countries, and are subject to modification from time to time.
Each country has its own special enactments relative to the method of dealing with roads, rivers, streams, and public and private property proposed to be interfered with in the construction of any line, and a knowledge of these is absolutely necessary for the promoters of any new scheme, inasmuch as some of the requirements may, in certain instances, influence the precise route to be selected.
The English Government has passed several Acts of Parliament setting forth the general conditions which must be complied with in the construction of any railway in the United Kingdom. These conditions, or standing orders, relate both to the acquirement of land and property, the size and description of works for public or private accommodation, and the inspection and official approval of the undertaking when completed. These fixed regulations are alike valuable to the promoters and to the public; the former are informed of the principal points with which the scheme must conform, and the latter know the limit of their legal demands.
No line of railway, or extension of any railway, will obtain Parliamentary sanction unless it can be satisfactorily proved in the outset, that its construction would be of public advantage. This point is of paramount importance, and due weight must be given to it when preparing to refute the evidence of opponents to the scheme.
When conceding the right to make any railway, Parliament grants with it the power to purchase lands or property compulsorily, or by agreement, to change and divert roads and streams in the manner shown on the deposited plans, and to construct all necessary bridges and works in accordance with the standing orders, or such modifications of them as may be approved by the Board of Trade.
The standing orders, or Government regulations, are very comprehensive, and include much detailed information on all questions likely to arise. The following brief summary of some of the principal orders relating to deposited plans, and works of construction, will be found useful for reference.
Extract from Government Standing Orders and Regulations.—All plans and sections relative to proposed new railways must be lodged with the constituted Government Authorities on or before November 30.
Every deposited plan must be drawn to a scale of not less than four inches to a mile, and must describe the centre line, or situation of the work (no alternative line being allowed), and must show all lands, gardens, or buildings within the limits of deviation, each one being numbered with a reference number, and where powers to make lateral deviations are applied for, the limits of such deviation must be marked on the plan.
Unless the whole of such plan be drawn to a scale of not less than 400 feet to an inch, an enlarged plan must be drawn to that scale of every building and garden within the limits of deviation.
The Railway Clauses Act limits the extent of deviation to 100 yards on each side of the centre line in the country, and 10 yards on each side of the centre line in towns or villages.
The distances must be marked on the plan in miles and furlongs from one of the termini.
The radius of every curve not exceeding one mile must be marked on the plan in furlongs and chains.
In tunnels the centre line must be dotted, but no work must be shown as tunnelling, in the making of which it is necessary to cut through, or remove the surface soil. If it is intended to divert or alter any public road, navigable river, canal, or railway, the course and extent of such diversion, etc., shall be marked on the plan.
When a railway is to form a junction with an existing railway, the course of such existing railway must be shown on the plan for a distance of 800 yards on each side of the proposed junction. In the case of Bills for constructing subways, the plans and sections must indicate the height and width of such subway, and the nature of the approaches by which it is proposed to afford access to such subway.
The Book of Reference must contain the names of all owners, lessees, and occupiers