HEADQUARTERS ARMY OF THE POTOMAC,
October 5, 1862.

Colonel A. T. McREYNOLDS, Green Spring:

Colonel Averell was ordered last night to proceed from Williamsport to the vicinity of the Big Cacapon, to operate against the rebel forces. I have telegraphed to him, via Hagerstown, to move rapidly up to join you in the pursuit, but, as he may not receive my dispatch, you will please send messengers on the different roads, to communicate with him as rapidly as possible, informing him of everything you know in relation to the enemy's movements and the enemy's movements and the movements of your own troops.

R. B. MARCY,

Chief of Staff.

GREEN SPRING, October 5, 1862.

General R. B. MARCY, Chief of Staff:

Your dispatch this day received. I have sent detachments on all routes by which Colonel Averell can approach this vicinity, to communicate and co-operate with him. Imboden retired to Big Cacapon Bridge, arriving there probably this evening. Eight companies of my command, under Captain Boyd are hard after him. My entire effective force in very small, only about 700 men, and horses almost entirely exhausted. I have sent out all I can spare, and retain adequate protection for the railroad. I have to report, additional to details given this morning, the utter destruction of Imboden's camp, the haversacks, clothing, and baggage of his entire command, 100 muskets, 3 wagon-loads of musket ammunition, a large quantity of quartermaster and commissary stores, his entire wagon-train, bringing away ambulances, two brass mountain howitzers, a large of canister, ball, and friction primers, leaving behind nothing. Among the prisoners whom I have sent to Cumberland were a major and lieutenant.

A. T. McREYNOLDS,

Colonel, Commanding Brigade.

Copy to General Pleasonton, commanding Cavalry Division, Harper's Ferry.

HEADQUARTERS FOURTH CAVALRY BRIGADE,
Green Spring, Va., October 5, 1862-4 a. m.

I have ascertained positively that the raid yesterday was committed by Imboden, with 1,500 cavalry and 1,000 infantry. During the time that Imboden was absent from his camp, a detachment of the First New York Cavalry, under Captain W. H. Boyd, made a raid on his camp dispersing the enemy in superior force, capturing 25 prisoners, 2 pieces of artillery, 10 wagons, 20 mules, and 25 horses, together with al of Imboden's private papers, and other papers of great interest. This took place on Blue's Gap, or Hanging Rock, on the South Branch, The bridge is covered by my pickets.

A. T. McREYNOLDS,

Colonel, Commanding.

General R. B. MARCY,

Chief of Staff.