HEADQUARTERS DEPARTMENT OF THE SHENANDOAH,
Near Harper's Ferry, Va., August 4, 1861.

Colonel LEONARD,

Thirteenth Regiment Massachusetts Volunteers:

SIR: The general commanding directs that you proceed to Sharpsburg, Md., near the Potomac River, and there take post until further orders. You will detach from your regiment the following number of companies, to take post as follows.

Two companies at Antietam Ford; two companies at the ford a short distance below Sherpherdstown; one company at the ford at Shepherd's Island, some distance above Shepherdstown; one company at the ford a short distance below Dam Numbers 4.

You will instruct the commanders of these detachments to be particularly on the alert, in order to put a stop to all contraband trade in the vicinity of their posts; to put a stop to all treasonable correspondence, without interfering with the United States mail, should there be one, and to arrest all persons engaged int reasonable acts, against whom sufficient proof can be obtained. it is the general's wish that travel between Maryland and Virginia be stopped, except with persons of proved loyalty to the United States Government. He relies freely upon the discretion, energy, and good judgment of yourself and your subordinates for carrying out the above instructions.

The detachment of U. S. cavalry now at Antietam Ford will be relieved from duty at that post upon the arrival of your detachment.

I am, very respectfully, your obedient servant,

ROBT. WILLIAMS,

Assistant Adjutant-General.

HEADQUARTERS DIVISION OF THE POTOMAC,
Washington, D. C., August 6, 1861.

Brigadier General I. MCDOWELL,

Commanding Department of Northeastern Virginia, Arlington, Va.:

Information I have received induces me to caution you to be carefully on your guard to-night and to-morrow morning against an attack by the enemy. Left Hunt hold at least two batteries ready to move to this side, if necessary, at the shortest notice. Communicate this to Franklin, Kearny, Blenker, and Sherman.

GEO. B. MCCLELLAN,

Major-General, Commanding.

CAMP TENNALLY, August 6, 1861.

Major S. WILLIAMS, Assistant Adjutant-General:

MAJOR: I made this morning a reconnaissance of the country reported last evening to be occupied by the enemy, by an officer I had sent to examine the country in front of the point at which my pickets communicate with those of Colonel Smith, of the Vermont regiment. I discovered that what he had supposed to be camps of the insurgents proved to be, under the scrutiny of the glass, only clusters of whitewashed houses, negro cabins, and fences on the opposite side of the Potomac.

I afterwards persecuted the examination of both banks of the river as far as the head of the aqueduct, but discovered no signs of the presence