Don't advance your troops unless absolutely necessary, as the general commanding desires to keep your command fresh to follow up a repulse, which he thinks will be a necessary result if the enemy attacks.

If there is any unfinished work on your bridges, please push them as rapidly as possible.

A. V. COLBURN,

Assistant Adjutant-General.

Reserve ammunition will be loaded in wagons, ready to send forward as soon as your ordnance officers call for it, at the ammunition landing. You had better push it up as rapidly as possible.

HEADQUARTERS ARMY OF THE POTOMAC.

Camp near Harrison's Landing, July 6, 1862.

Brigadier-General KEYES,
Commanding Fourth Corps:

GENERAL: Information, supposed to be reliable, has reached these headquarters that the Confederate forces under Lee, with Longstreet, Jackson, Johnston, &c., are very near us in front of our whole line, and that an attack may be expected at any moment.

The general commanding directs that you have your command under arms a little before daybreak, your batteries in position, your men on the alert, and your pickets as well thrown out as possible.

Endeavor to get Couch's division in position as soon as possible after daylight concerting the movement with General Heintzelman and Hooker.

Use the fewest possible number of troops consistent with security to repel the first attacks of the enemy in order to bring up fresh troops to oppose his renewed attacks.

The corps of General Sumner is in reserve to support your corps and that of Heintzelman. The entire corps of Porter is also in reserve on the right, ready to be thrown to any point it may be needed.

Inform the general at once what ammunition you need and what caliber you require.

The gunboats will cover your flank effectually and fully, and if the trees have not been cut down which intercept the view of the gunboats, put a heavy additional force at once to accomplish that important object.

If within an hour after daylight you are not attacked, you are to put your working parties to work in completing your defenses.

Be sure to establish by means of flags the range for the gunboats and to have a signal officer on duty with you.

The reserve ammunition loaded up. Send your ordnance officers to the depot to see to the matter, that ammunition loaded up. Send your ordnance officers to the depot to see to the matter, that ammunition may be brought up with certainty ad celerity as it may be required.

The General Headquarters will be established, in case of an engagement, at the barn near Sykes' headquarters. The spot will be indicated by a small national color. In the event of the headquarters leaving the place, aides will remain to designate the place they have gone to.

Communicate frequently to headquarters as to the progress of affairs, at least once every half hour in case of an engagement,and always in writing, if possible.

I am, general, very respectfully, your obedient servant,

A. V. COLBURN,

Assistant Adjutant-General.