The Photographic History of The Civil War: in ten volumes, Thousands of Scenes Photographed 1861-65, with Text by many Special Authorities, Volume 5: Forts and Artillery.
Francis Trevelyan Miller, Ed.

Consequently, the work had to be postponed until daylight, but communication was opened with the opposite bank by 8:15 A. M. Soon another span was built, and the troops were engaged in road-making in the vicinity of the two river-crossings, to keep open the passages across the low, swampy lands through which the river runs. A third structure, of combined cribwork and trestle, was then constructed, some distance below the two pontoon bridges. Of this last passageway, General Barnard, chief engineer of the Army of the Potomac, remarked that it was an excellent structure, capable of bearing all arms and affording direct communication, in place of that by the inconvenient roads across the pontoon bridges.

At Mechanicsville and Gaines' Mill, the engineer troops did valiant service in the construction of trenches and other field-works. By this time the other troops were gaining the necessary experience, and toward the end of the Peninsula campaign the hastily constructed entrenchments of the entire army were models of completeness and speed in building. Road-work, in this desolate region, was of the most fatiguing kind, but was well and thoroughly done. The few men available from the engineer battalion aided as the instructors of the other troops engaged, and, by the time the movement began toward Malvern Hill, nearly all the troops of the Army of the Potomac had become accomplished in the arts of roadmaking, bridge-building, and entrenching. At Malvern Hill, the engineer battalion was posted as infantry, after preparing the front of the line by “slashing” or felling trees, to impede the advance of the Confederates and to afford an open field of fire to the defending troops.

After leaving Harrison's Landing on the withdrawal from the Peninsula, the battalion was sent to Fort Monroe to replenish its materiel, and thence to the mouth of the Chickahominy, where, in a short time, a fine pontoon bridge was constructed for the passage of McClellan's entire army.

This bridge was 1980 feet long, and for the most part was