This great force--for each engineer has gathered about him a competent staff of young men as expert with compass, with level, and with transit as were the men who first projected the line--is in the field as quickly as the contractor. They are to see him bring the line to sub-grade; to see him place bridges and culverts, bisect high hills with cuttings, bore tunnels through even higher hills and mountains, span deep valleys with great embankments. To facilitate quick construction the residencies are made numerous; work begins at as many initial points as possible. These points, of course, are situated, where possible, close to water communication or existing railroad lines, in order that material may be brought with the least possible delay and expense.
Of course, if the country has a sharp contour, the ordinary difficulties of line-construction multiply very rapidly. The great cuttings through the hills may have to be carved out of resisting rock, a work that is carried on through many levels, known to the engineers as ledges or as benches. If there are high hills to be notched there will probably be great hollows where the circumstances do not justify carrying the line on bridge or trestle. In these cases come the fills, or embankments. We have already shown how the locating engineer in the first instance has tried to plan his line so that the earth or rock from his cutting will be as nearly as possible sufficient to form the near-by embankments. Sometimes it is not, and then the resident engineers must locate borrow-pits, where the hungry demand of the railroad for dirt will cause a great hollow to show itself on the face of the earth. The borrow-pit must be carefully located--convenient of access, far enough from the track not to be a danger spot to it. This is one of the infinity of problems that come to the construction engineer.
For these big jobs laborers' camps will be established close to them; and small temporary railroads peopled with hordes of restless dummy-engines and forcing their narrow-gauged rails here and there and everywhere, will be busy for long weeks and months. There will not be much hand-cutting in the ledges. Steam shovels, mounted like locomotives upon the rails, and pushing forward all the while, will fairly eat out the hillside. One of these will catch up in a single dip of his giant arm more than a wagon load of soft earth or of rock that has been blasted apart for his coming.