RAILWAY CONSTRUCTION. 33 



out by driving strong wooden pegs into the ground at the end of 

 every chain length, and along the course of these pegs the longi- 

 tudinal section must be taken. Three pegs, one on each side of 

 the centre peg, are generally placed at the commencement and 

 termination of the curves. When the longitudinal section has 

 been plotted to scale, and the course of the gradients and level 

 portions worked out and drawn on, then the heights of the 

 ground level and formation level can be marked at each chain, 

 and from them the depths of the cutting and the heights of the 

 embankments can be ascertained and marked at each chain. In 

 addition to the longitudinal section, it will be necessary to take 

 a large number of transverse or cross sections at those pegs, or 

 intermediate points, where the ground is at all side-lying or 

 irregular. These cross-sections are necessary to determine the 

 side- widths, or distances to outer edge of slopes in cuttings or 

 embankments, and also to calculate the actual quantity of earth- 

 work to be executed. For convenience in taking out the 

 quantities, these cross-sections are generally plotted to a natural 

 scale, that is to say, to the same scale horizontal as vertical, as 

 shown in the example of cross-sections, Figs. 15 to 24. It 

 is also necessary to obtain information, by boring or otherwise, 

 as to the material of which the cuttings are composed, whether 

 clay, gravel, or rock. 



In laying out lines through fairly level plains and populous 

 districts, the absence of great natural obstacles will allow the 

 engineer to carefully consider how far it may be prudent to 

 diverge to the right or to the left, to accommodate towns and 

 places which would be excluded by a more direct through route. 

 There will be ample range for selection, and it will be rather the 

 question of policy than compulsion which will guide him in the 

 route to be taken. 



When, however, the locating passes from the lower ground, 

 away up amongst the hills and mountain ranges, it becomes an 

 intricate study whether it will be possible to lay out any line at 

 all which may possess gradients and curves practicable for 

 railway working. The question of property, population, or con- 

 venience of access, is here no longer the controlling influence, 

 but in its stead there are the far more formidable natural 

 difficulties to be overcome in working out a trackway to the 

 inevitable summit level. The chief endeavour will be to gain 

 length, and so reduce as much as possible the steepness of the 



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