the bridge finished at noon yesterday. When the bridge was completed yesterday I returned to camp, leaving the approach at the south side of the river to be built by Captain Chester. During the construction of the bridge the approach on this side was built by Captain Perry, of the Fifteenth, who also rendered me valuable assistance in securing the north end of the bridge. With the slight changes suggested by you to accommodate the bridge to the falling or lower stage of the water, and which I hope to have finished before the south approach is ready for use, the bridge is perfectly secure for infantry in two ranks, and as safe for the passage of artillery as this plan of trestle can be made without strengthening it beyond the original plan. Of the time required to complete the south approach I am not able to speak with any certainty, as I am not familiar with the ground.

Very respectfully,

I. SPAULDING,

Captain Fiftieth New York Volunteer Engineers,

Commanding Detachment Engineer Brigade.

Brigadier General D. P. WOODBURY,

Commanding Engineer Brigade.

No. 5. Report of Brigadier General Andrew A. Humphreys,

U. S. Army, Chief of Topographical Engineers.

HEADQUARTERS THIRD DIVISION, FIFTH CORPS, February 20, 1863.

GENERAL: In compliance with a request received through Brigadier General S. Williams, assistant adjutant-general, that I would make a report upon the operations carried on under my directions while serving as chief of topographical engineers with the Army of the Potomac, I submit the following hurried and imperfect sketch, regretting that the circumstances by which I am surrounded render it difficult for me to present even this meager account:

About December 1, 1861, I was assigned to special duty on the staff of Major-General McClellan, commanding the Army of the Potomac, and when that army took the field came into command of the officers of my corps serving with it. Previous to taking the field every available source was exhausted that promised to furnish information, general or special, respecting the character of the region in which the operations were to be conducted. The topographical information obtained was, however, very meager, and continued, careful reconnaissance was necessary to guide the march of the warious portions of the army, to exhibit the relations between them, and to designate the positions for depots and the lines of supply. Reconnaissances were likewise made of the enemy's several positions-at and near Yorktown, on the Chickahominy, and on the approach to Richmond from that stream, and also of the positions occupied by our army at Yorktown, on the Chickahominy, and at Harrison's Landing. From these reconnaissances detailed maps of the scene of operations were prepared, multiplied by photography, and distributed to the commanders and staff officers of the various subdivisions of the army. It is not necessary that I should enumerate the various reconnaissances that were made and the particular object of each. A list of the chief maps that resulted from the