per's Ferry, and in my orders of movement for to-morrow have arranged so that I can go or send to his [Miles'] relief, if necessary. I have heard no firing in that direction, and, if the resists at all, I think I can not only relieve him, but place the rebels who attack him in great danger of being cut off. Everything moves at daylight to-morrow. Your message to him this moment received. Will forward by first opportunity.

GEO. B. McCLELLAN,

Major-General, Commanding.

HEADQUARTERS ARMY OF THE POTOMAC,
Camp near Urbana, September 12, 1862-9 p. m.

(Received 6.50 a. m., 13th)

His Excellency the PRESIDENT:

You will have learned by my telegram to General Halleck that we hold Frederick and the line of the Monocacy. I have taken all possible means to communicate with Harper's Ferry, so that I may send to its relief if necessary. Cavalry are in pursuit of the Westminster party, with orders to catch them at all hazards. The main body of my cavalry and horse artillery are ordered after the enemy's main column, with orders to check its march as much as possible, that I may overtake it. If Harper's Ferry is still inn our possession, I think I can save the garrison, if they fight at all. If the rebels are really marching into Pennsylvania, I shall soon be up with them. My apprehension is that they may make for Willamsport, and get across the river before I can catch them.

GEO. B. McCLELLAN,

Major-General.

HEADQUARTERS RIGHT WING,
Two Miles North of Damascus [Md.], September 12, 1862-5.30 a. m.

(Received 1.30 p. m.)

Major-General HALLECK,

General-in-Chief, and

Major-General McCLELLAN:

A squadron of cavalry has just returned from New Market, and gives us the positive information that the place was evacuated yesterday, the rear leaving at 5 p. m. The force there consisted of four regiments cavalry and six pieces artillery, under Fitzhugh Lee. The regiments were small when they first arrived, and in very bad condition, both horses and recruits. Their arms are said to be bad. They had no wagons and about fifty head of cattle. Their main body probably encamped last night at Liberty; their rear at New London. The soldiers all say they are going into Pennsylvania. This much of the information is reliable. The commanding officer of the squadron conversed with some of the citizens of New Market who had been in Frederick, and they all agree in representing that Jackson had been there with a very strong force, and has moved from there in the direction of Hagerstown; and it is also rumored that columns have moved upon the Gettysburg and Harper's Ferry roads. I can hardly understand how they can be moving on these two latter roads at the same time. I f they are going into Pennsylvania they would hardly be moving upon the Harper's Ferry road,