Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/250

Rh 232 RAILWAY by the railways then in operation, independently of the consider- able amount of labour employed on railways in course of construc- tion. On 31st March 1884 railway employes numbered in all 367,793 persons, or 19 '69 per mile open, showing an increase of more than 50 per cent, on the proportion per mile in 1857, which was only 12'63. Table XXIV. gives details : Persons. Per Mile. 4,199 781 74,177 69,713 23 04 3'-97 3-73 6'-33 4-32 15 10 01 20 43 18 Superintendent's departments Superintendents and assistant superintendents. . 143 16,178 1,889 5,902 19,012 2,0(50 29,493 1 Guards i Signalmen and pointsmen Shunters, porters, messengers, &c Goods and assistant managers 113 17,058 963 7,410 44,169 Guards and brakesmen 125 248 2,013 47,130 25,669 43,141 118,326 80,609 2,820 1,781 222 3,754 8,004 3,407 Clerks . Engineer's departments- Engineers and assistant engineers 201 585 782 1,166 8,020 10,539 59,316 Clerks Inspectors Telegraph Hotels, refreshment-rooms, and sundries Total 307,793 19-09 From this table it may be estimated that there are now two drivers and two firemen for every 3 miles of line open. In 1857 there were only two drivers and two firemen for every 5 miles ; and, though the train service has increased faster than the train mileage, the work of the drivers has sensibly diminished, each man on an average doing 20,950 miles as against 23,420 in 1857. RAILWAY CONSTRUCTION. The selection of lines of railway is mainly governed by the same principles as hold good for roads, but the cost of the rails renders it of greater importance to shorten the length of the route than to make slight savings in embankments and cuttings. The first step in the survey is to ascertain the positions of the watercourse and watershed lines of the district to be passed through. The general direction having been selected by the help of an ordnance map, a sketch-map, or a special reconnaissance survey, the river-crossings are to be examined and decided upon, and the points determined at which the watersheds are to be crossed and the approaches to bridges set out. Trial lines should be run between the points thus fixed, and the country should be carefully examined on each side of these before the route is finally decided on. Sharp curves and steep gradients are in themselves evils, involving special cost for maintenance and for working, although original outlay may be economized by the adoption of them. A straight and horizontal surface is assumed as the standard of perfection ; and the proper business of the engineer in laying out a railway is to harmonize the engineering and the financial conditions of the problem so as to yield the highest practicable return on the money expended, and to see that, whilst the railway may be neither quite straight nor quite level, it shall not be unduly costly in construction from ex- cessive cutting, tunnelling, and making of embankments, in order to obviate severe curves and gradients, nor excessively cheap from following the surface of the ground too closely and incurring heavy gradients and severe curves, and as a consequence heavy working expenditure. Cuttings and Embankments. Engineers endeavour so to plan the works of a railway that the quantity of earth to be excavated shall be equal to the quantity that goes to form the embankments. The earthwork is the foundation and support of the superstructure, and as such it must be uniformly firm, of liberal width, easy slopes, thorough drainage. Figs. 10 and 11 are type-sections of cuttings and embankments for a double line of way on the national gauge, showing the "formation" surface and the ballast on which the permanent way is supported, with the slopes, the side drains, and the fencing. Fig. 12 is a type-section of the ]>ermanent way on the national gauge, settled by Mr John Fowler for the South Wales Railway. Upon the formation level the ballast is deposited, 2 feet in depth at the centre, dressed level, for about 22 feet in width for a double line of way. The sleepers and chairs are buried in the Ktifs FIG. 10. Type section of a cutting. ballast, and the rails partially also, these standing 2 or 3 inches above the ballast. The intermediate space between the two lim-s of way is, as before stated, 6 feet, and, taking the lengths of the // of a,its FIG. 11. Type section of an embankment. sleepers at 9 feet, the total width for two lines of way over the sleepers is 6 feet + 4 feet 8J inches + 2 inches x 2 (width of the rails) + 9 feet = 20 feet 1 inches ; and it is seen that, as the /-^=&z=Z _ A. , Jil^ z A. . X FIG. 12. Type section of permanent way. ballast is 22 feet wide at the upper surface, it extends to nearly 1 foot beyond the ends of the sleeper at each side and about 3 feet beyond the outer rails at each side. _ The slopes of cuttings vary according to stratification, soil, direc- Cuttii tion of the vein, moisture. In gravel, sand, or common earth the slopes rise 1 foot for 1 to 1J or 2 feet of base ; in solid rock the slopes are nearly vertical. Cuttings are as deep as from 50 to 1 00 feet below the surface, and embankments as high above. The London and Birmingham Railway had upwards of 12 million cubic yards of excavation, and 10J millions of excavation in the original estimates, or above 100,000 cubic yards of earthwork per mile. The heaviest cutting on the line is at Tring, 2 miles long, averag- ing 40 feet deep, the greatest depth being 60. In the case of the great Blisworth cutting the strata were unequal in consistency. About halfway up the face of the cutting a stratum of limestone rock, 25 feet in thickness, was found, with loose strata below and above it, and it was necessary to prevent the lower stratum, con- sisting of wet clay, from being forced out under the superincum- bent mass by undersetting. A rubble wall, averaging 20 feet in height, was built on each side underneath the rock, strengthened by buttresses at intervals of 20 feet, resting on inverted arches carried across underneath the line. A puddle -drain was formed Flo _ 14. FIG. 13. Blisworth cutting; west end. behind each wall, with a small drain through the wall to let off the water from behind. Fig. 13 is an elevation of the west end of the cutting where it is about 40 feet deep, show- _^r ing clearly the method -_^ of undersetting, and fig. 14 is a cross section of^ the side walls at the' same place, where the left-hand shows a sec- tion of the wall in the water, and the right-hand side shows the section through a buttress, together with the invert and drains. One of the walls is shown in front elevation in fig. 15. The New Cross cutting through the London clay, on the South-Eastern Railway, is 2 miles long, and is for some, distance from 80 to nearly 100 feet in. depth. This cutting affords an example of the tendency of some soils to slip. The slopes of the cutting were finished at 2 horizontal to 1 vertical ; and they remained as thus finished for FIG. 15. Wall of the same cutting.