I am convinced that the risk to life to the engineers and men on that railroad fully equaled that on the skirmish-line, called for as high an order of courage, and fully equaled it in importance.

Still, I doubt if there be any necessity in time of peace to organize a corps specially to work the military railroads in time of war, because in peace these same men gain all the necessary experience, possess all the daring and courage of soldiers, and only need the occasional protection and assistance of the necessary train-guard, which may be composed of the furloughed men coming and going, or of details made from the local garrisons to the rear.
For the transfer of large armies by rail, from one theatre of action to another by the rear--the cases of the transfer of the Eleventh and Twelfth Corps--General Hooker, twenty-three thousand men--from the East to Chattanooga, eleven hundred and ninety-two miles in seven days, in the fall of 1863; and that of the Army of the Ohio--General Schofield, fifteen thousand men--from the valley of the Tennessee to Washington, fourteen hundred miles in eleven days, en route to North Carolina in January, 1865, are the best examples of which I have any knowledge, and reference to these is made in the report of the Secretary of War, Mr.Stanton, dated November 22, 1865.
Engineer troops attached to an army are habitually employed in supervising the construction of forts or field works of a nature more permanent than the lines need by the troops in motion, and in repairing roads and making bridges.

I had several regiments of this kind that were most useful, but as a rule we used the infantry, or employed parties of freedmen, who worked on the trenches at night while the soldiers slept, and these in turn rested by day.

Habitually the repair of the railroad and its bridges was committed to hired laborers, like the English navies, under the supervision of Colonel W.W.Wright, a railroad-engineer, who was in the military service at the time, and his successful labors were frequently referred to in the official reports of the campaign.
For the passage of rivers, each army corps had a pontoon-train with a detachment of engineers, and, on reaching a river, the leading infantry division was charged with the labor of putting it down.
Generally the single pontoon-train could provide for nine hundred feet of bridge, which sufficed; but when the rivers were very wide two such trains would be brought together, or the single train was supplemented by a trestle-bridge, or bridges made on crib-work, out of timber found near the place.

The pontoons in general use were skeleton frames, made with a hinge, so as to fold back and constitute a wagon-body.