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of which will probably take some time, field railways turning them must be constructed. Where the railway network is altogether insufficient to satisfy the wants of the army, or where too many difficulties are encountered in repairing the trunk lines, field railways must be laid along lines of advance from railheads. There is no occasion in these cases for being too pedantic in constructing such lines. They are not built to last for ever, and must sometimes be rapidly taken up again. At times horse power must suffice for them until time and circumstances permit the line to be constructed for steam power. Rapidity of construction is the first object. If the line to be constructed is long, we must try to begin building it at various points simultaneously. We must try to follow each corps, if possible, with one field railway line, provided material and personnel are available to build it, which of course is not the case to an unlimited extent."

Gen. von Kluck, in his book The March on Paris, says:

" To assist the work of supply, a light railway system up to the

several corps was successfully opened for traffic on Aug. 22 (1914) ;

that for the II. Corps to Ninove and Vollezeel ; for the IV. Corps at

first to Castre, later to Enghien; and for the III. Corps to Hal."

These two quotations are sufficient to establish the fact that the Germans had adopted these lines as an essential part of the open warfare equipment of an army marching to attack, and not as an expedient for trench warfare. Experience at Metz, at Toul, and at the tunnel of Nauteuil in 1870, had impressed the minds of the German general staff with the need of some means for supplying the several corps of an army attacking an enemy army just beyond or pivoting on an obstacle on the main railway line. Doubtless they had, with their usual attention to detail, selected the ig-lb. rail, 6o-cm. Decauville track, as the lightest which could accommodate the locomotives and cars necessary to for- ward a daily corps supply of ammunition and food for a serious engagement (about 600 tons for the German corps of 1914).

This character of service was rendered by the 6o-cm. lines in the open warfare attacks by the American army in 1918. Rapidly extended for each corps, they served to free the roads and stand- ard-gauge railway terminals from congestion by animal and motor transport, and thus gave a freedom of manoeuvre for the troops engaged in breaking the hold, which the enemy insisted on maintaining, on the valleys where standard-gauge lines existed or where they could be built. For example on the American front in the attack N. from Verdun-Ste. Menehould railway, two standard-gauge lines were contemplated for the supply of the army. One of these followed the Meuse river valley to Stenay and Sedan. The enemy clung desperately to this line, and it was not until the III. Corps supplied by " soixante " forced a cross- ing of the river at Dun-sur-Meuse that the valley was freed and the reconstruction of the standard-gauge line could proceed. The " soixante " had given the power of manoeuvre required. The second was the Aubreville-Grandpre-Mouzon line. For the attack on Verdun, the Germans had constructed a standard- gauge railway line from Mouzon to Grandpre, where it connected with a French standard-gauge railway leading to Ste. Menehould. The American plan was to build a line from Aubreville to Grand- pre and thence along the German roadbed to Mouzon. Work was put under way at the beginning of the advance, Sept. 26 1918, the line being constructed as far as, and to include, a terminal at Varennes under standard-gauge railway practice. From Varennes, the " soixante " reached out to the east to supply the V. Corps, and the manoeuvres of that corps and of the I. Corps on its left, supplied from Varennes and also by " soixante " from Les Islettes, freed Grandpre and opened the Aire valley for the advance of the standard-gauge railway, which from Varennes northward was constructed in accordance with light railway practice, no ballast being used, the track being supported by ties almost in juxtaposition, alternate ties extending outside of track to permit tamping and to spread the foundation. In advance of the standard-gauge track, and on the same roadbed, a " soixante " line was laid, partly of fabricated track and partly of separate rail construction, on standard ties. While this was pushed ahead of the standard line, primarily for the supply of troops, it served to speed up the construction of the standard railway by handling materials, rails, and ties in advance of standard railhead. Points of transfer from standard gauge to the " soixante " were ad- vanced as terminals permitted and as desired, and when so

advanced the " soixante " material in rear of transfer point could be taken up if needed. This was rarely done, as the line to the rear was useful.

Ever since the days of Sevastopol, students of siege warfare had insisted upon a railway for use both by the attack and de- fence in fortress warfare. An i8-in. gauge had been adopted for these siege railways, and 5-5 m. of this track were to be carried as a part of the regular authorized store of a siege train in British practice. This equipment, including wooden sleepers but exclud- ing cars, weighed approximately 62 tons to the m.; 25 trollies on two four-wheel bogies, weighing 54 tons, were also to be taken. The siege train included 16 pieces of artillery. For similar pur- poses the French had adopted a Decauville pattern track of 40- cm. gauge (16 in.). In the original conception of these hand- operated lines of from i6-in. to i8-in. gauge, the ordinary gauge of the country was to be brought to the field arsenal (siege junc- tion), and the break of gauge between it and the narrow-gauge lines was to be made there, though it was accepted that under certain circumstances lines of wider gauge would be pushed for- ward to the front, even to the first batteries, independent of the break in gauge at the field arsenal. The British Siege Artillery Drill Book in 1898 estimated the distance of the siege arsenal at 7,000 yd. from the fortress, as being out of range of the defence guns, and this distance and the width of front to be covered by a siege unit formed the basis for the estimate upon which the 5^ m. of siege track per unit was arrived at. But increases in range, and particularly in accuracy and effectiveness of fortress guns, caused a new estimate to be made of the distance to the siege arsenal, and led to a realization that not only ammunition but other stores as well would need to be more widely dispersed, not for security alone but also for better service. Such changes increased unduly the length of haul and led to the adoption of a light line suitable for locomotives.

During the World War, after position warfare was entered upon and lines became more and more permanent, the daily wear and tear led to the replacement of light rail by heavier, the improvement of the roadbeds, the increase of ballast, the increase of loads, the connecting up of separate detached lines into systems, the installation of shops and other facilities pertaining to com- plete systems, and a tendency, as evinced by the action of the Americans, to adopt heavier rolling-stock and more powerful locomotives so as to secure greater tonnage per engine and train mile. Unquestionably at this period, had the design de nemo of a railway to meet the then existing conditions arisen, most officers would have favoured a wider gauge. But when the advance be- gan once more, the weight of a mile of track, including sleepers, came to be a vital one and the " soixante " reverted to type. Then the heavy engines and heavy cars, still very useful in bringing up materials of construction from the rear, came to be, temporarily at least, out of place on the forward lines.

In their simplest diagrammatic form the " soixante "lines ran perpendicular to the front, from stations along a standard-gauge line which roughly paralleled the front. These perpendicular lines were connected by laterals, the whole forming a series of loops, and trains were operated out on one line and back on an- other. The loop system permitted a density of traffic exceeding that of double track lines, and offered an alternate route if the track was broken at any point. Most of the grading was done by hand, and every effort was made to reduce earth work by follow- ing the contour of, the ground even when rather sharp curves resulted. Surface location was also advantageous because it permitted a shifting of the track in repair of a break made by shell-fire. Embankments were especially to be avoided, as hand- made fills in a rainy climate meant soft track and washouts.

A most difficult problem in track construction was met with in crossing badly shell-torn ground. Old craters were half-filled with water. To level off and proceed with track -laying meant certain trouble later. Here wooden ties were used to great ad- vantage, the fabricated track, spiked down occasionally, being frequently laid on a roadbed formed by them, the ends being supported if necessary on crib work in a manner customary in the repair of washed-out track in America.