CENTREVILLE, October 19, 1862-9.30 p. m.

Captain ASMUSSEN,

Fairfax Court-House:

The three runaways have made a false report. Captain Conger and his men have returned and taken the road either to Fairfax Court-House or Fairfax Station. They were beyond Catlett's Station, and drove the enemy until they found him in force. Let the two companies proceed to Fairfax Station, as your ordered.

F. SIGEL,

Major-General.

HEADQUARTERS OF THE ARMY, Washington, October 20, 1862.

Major-General McCLELLAN,
Commanding, &c.:

GENERAL: Captain J. C. Duane's letter of the 17th, with your indorsement of the 18th, was picked up in the street near the railroad depot, in this city, on the evening of the 19th.

I concur with you in opinion that Maryland and Loudoun Heights should be fortified and occupied; but I think that field fortifications and redoubts would be sufficient for the purpose, without incurring the expense of constructing permanent works, stone redoubts, &c. Harper's Ferry is not, in my opinion, a proper base of military operations, and it would be an error to expend time and money there for such an object.

Substantially these views have been indorsed on your communication, and submitted to the Secretary of War, who approves them.

Very respectfully, your obedient servant,

H. W. HALLECK,

General-in-Chief.

OCTOBER 20, 1862.

General MARCY,

Chief of Staff, Present:

DEAR GENERAL: I have been absent to-day, at Harper's Ferry, and received your note this moment.

I have taken the most effective measures in my power to procure the horses at once. General Averell was authorized to purchase his (400) two days ago.

Captain Reno, with two officers, left to-day, with T. Scott Stewart, for Harrisburg, Pittsburgh, &c., to buy 2,000 more, and Captain Reno is directed to use Mr. Colder as an agent. Several of the artillery officers are authorized to buy for their service. Captain Robertson, of the Second, leaves in the morning with Mr. Bishop to buy 5,000 artillery horses. Had authority been given me sooner, of course I should have had the horses ere now. I suspect we shall be some ten days in obtaining the number required. Meantime I can count on some 1,500 from Washington, I am told. I have ever tried all in my power to keep the number up to requirement. I am sure I would give all my expectations on earth for the success of this army and our generals. I know the clamor, and hope we many be in time. I wish the could move now.

Clothing is arriving now rapidly at Harper's Ferry. I would advise no delay on that account. If quartermasters will anticipate their wants