On Saturday, December 13, I received an order to lay the wire across the river. In less than twenty minutes from the time I received the order, the wire was laid and ready for operation at any moment.

On Monday evening, perceiving the troops recrossing, I succeeded, after a great amount of difficulty, in reeling my wire off the pontoon bridge, and am happy to inform you that during the engagement and in reeling up to headquarters I did not lose a foot of wire.

Messrs. Colton, of the One hundred and thirty-fourth Regiment Pennsylvania Volunteers, and Creigh, of the One hundred and twenty-sixth, operators, acquitted themselves with great honor, manifesting a spirit of genuine bravery during the engagement.

Messrs. Jones, of the One hundred and thirty-third Regiment Pennsylvania Volunteers, and Henginer, of the One hundred and fifty-fifth line men, though exposed to great danger, performed their part heroically, and deserve much praise for the skillful and acute manner in which they guarded the wire.

In my monthly report I will speak more fully of the working of the instrument.

I have the honor to be, your obedient servant,

DAVID WONDERLY,

Lieutenant and Acting Signal Officer.

Captain SAMUEL T. CUSHING,

Chief Signal Officer.

Numbers 15. Report of Lieutenant Cyrus B. Comstock, U. S. Corps of Engineers, Chief Engineer.

HEADQUARTERS ARMY OF THE POTOMAC,
Near Falmouth, Va., December 20, 1862.

SIR: I have the honor to submit an account of throwing pontoon bridges across the Rappahannock on the 11th instant, at Fredericksburg:

The following was the programme, which was in its main features carried out: Two bridges to be thrown at upper end of Fredericksburg, one at lower end, and two a mile below, making the distance between the extreme bridges nearly 2 miles. Lieutenant Cross, with Engineer Battalion, to throw the lowest bridge of all. General Woodbury's Volunteer Engineer Brigade to throw the others. Each bridge trains to arrive at bank of river at 3 a.m.; material to be unloaded and boats in the water by daylight, and bridges to be then finished in two or three hours, if not in the vicinity of the bridges, the ground rises rapidly from the river to a plateau half a mile wide, and from 30 to 50 feet above the river; back of this the ground rises again from 30 to 100 feet more, either into a ridge or a second plateau. This latter high ground commands the city of Fredericksburg and the ground behind it, and lower down the river, for from 1 to 2 miles from the right bank; there being on the left bank a plateau, some 30 feet above the river, but varying on the right bank in width from 1 to 2 1/2 miles. Along the highest ground on the left bank already spoken of, and along the edge of the plateau near the river, one hundred and seventy nine guns were put in position