WASHINGTON, June 13, 1861.

Major-General PATTERSON, U. S. A.,

Commanding, &c., Chambersburg, Pa.:

SIR: The General-in-Chief directs me to say that on the supposition you will cross the river Monday or Tuesday next (17th or 18th), Brigadier-General McDowell will be instructed to make a demonstration from Alexandria in the direction of Manassas Junction one or two days before. The General does not wish you to hasten, but keep him informed, so that General McDowell may properly time his movement.

Colonel Stone is advancing on Edwards Ferry and towards Leesburg, to intercept supplies and be governed by circumstances. If he finds means to communicate with you, and it is expedient to effect a junction with you, he has instructions to do so. The General has sent a man (William Johnston) to endeavor to pass through Harper's Ferry, and then to join you and give you useful information. It is hoped the facilities he seemed to possess will make his mission successful.

I have the honor, &c.,

E. D. TOWNSEND,

Assistant Adjutant-General.

CHAMBERSBURG, June 13, 1861.

Honorable SIMON CAMERON, Secretary of War, Washington:

SIR: On Saturday, the 15th, I propose to throw a strong force in front of Hagerstown, the remainder of the command to follow as speedily as my limited means of transportation will permit. We will then be beyond the telegraph, and have but one mail a day. The railroad company runs two trains a day, and the postmaster informs me that the additional cost of carrying the mail by both trains would not exceed fifty dollars a month. I venture to request that the contractors be directed to forward the mails twice in twenty-four to the Army under my command wherever located.

I have the honor to be, with great respect, your obedient servant,

R. PATTERSON,

Major-General, Commanding.

[Indorsement.]

JUNE 15, 1861.

Approved.

SIMON CAMERON,

Secretary of War.

WASHINGTON, June 13, 1861.

Major-General PATTERSON, Chambersburg, Pa.:

GENERAL: Information has been given the General-in-Chief that Ben. McCulloch has two regiments of sharpshooters coming from Texas, and that he is now on the spot preparing to meet your column, and then to fall back on Harper's Ferry.

Indications received from this side confirm the impression you seem to have that a desperate stand will be made at Harper's Ferry by the rebels. The General suggests that sharpshooters be met by sharpshooters.