Emmitsburg. I sent Lieutenant Ellis out from Frederick to try to communicate with Thayer, and sent word to Thayer to go toward Chambersburg and report often. General Crook having diverged by way of Middletown, I sent Lieutenant Merritt to Middletown to report to General Crook, and Lieutenant Fortney to Catoctin Mountain, near the road, to communicate with Merritt and headquarters at Frederick. This line kept General Crook in communication with headquarters during his march toward Emmitsburg. The enemy being reported at Noland's Ferry, General Hunter desired a station at Sugar Loaf and directed General Emory to furnish a guard for it. Accordingly I sent Lieutenant Brault, with twelve men, with orders to keep very vigilant watch, and also to send out scouts and report often. Lieutenant Ellis reported from High Rock that Chambersburg was burned yesterday; Couch gone to Carlisle; Averell has been at Greencastle and gone toward Gettysburg.

On the 1st of August, General Crook having moved out of sight of Fortney's station, he moved three miles north on the range and reopened with him. Lieutenant Brault came in to-night, having left the mountain when a force of 250 cavalry (rebel) had reached its foot (Sugar Loaf).

On the 2nd headquarters were removed to Monocacy. Lieutenant Ellis returned from Emmitsburg, and I called in Fortney from Catoctin.

On the 3rd I sent Lieutenant Merritt to Point of Rocks to open station of observation and to communicate with Sugar Loaf, which station I had re-established. I sent Lieutenant Brault with three sergeants and twenty-four men to patrol the river from Noland's to Edwards Ferry, to divide the distance into three beats and assign a sergeant with eight men to each beat, to report everything seen to Sugar Loaf. I also sent Lieutenant Fortney to Maryland Heights and Lieutenant Ellis to McClellan lookout, to start at 4 o'clock to-morrow morning, to report anything seen or learned of the enemy. If Averell was within reach Ellis was to direct Lieutenant Muhleman to take McClellan station and proceed himself to Fairview.

On the 4th these parties started out, and the line was opened and worked admirably to McClellan lookout. The following messages were received:

POINT OF ROCKS.

Citizens report Imboden at Leesburg with 1,500 men and four pieces of artillery. Conscripting. No other force east of Blue Ridge. Mosby gone into the Valley.

MARYLAND HEIGHTS.

Column of the enemy approaching Charlestown.

McCLELLAN-4 p.m.

Enemy approaching Harper's Ferry from Shepherdstown in force; four brigades of cavalry and infantry; large wagon train.

I signaled Ellis to estimate enemy's force and report frequently.

McCLELLAN-4.25 p.m.

Small party rebel cavalry in Sharpsburg.

McCLELLAN-5.20 p.m.

Enemy still move toward Charlestown.

McCLELLAN-5.40

I must leave; enemy very close to me.

Note.-Ellis had but six men and no guards.