Encountered Mosby's pickets, and drove them to the mountains. Mosby is beyond doubt again between New Baltimore and White Plains. No news from expedition sent to Thoroughfare Gap.

Respectfully,

W. D. MANN,

Colonel of Cavalry.

WASHINGTON, June 6, 1863.

General G. W. CULLUM,

Chief of Staff:

Dear General: Lieutenant [E.] Ball, Second Dragoons, reports that our troops occupy Fredericksburg, and that we are building another bridge. A colonel from there also made a report to Colonel [William A.] Nichols that our troops are in Fredericksburg. I inclose the telegram from General Stahel about General Buford's movement. Truly, yours,

S. P. HEINTZELMAN,

Major-General.

[Inclosure.]

FAIRFAX COURT-HOUSE, Va.,

June 6, 1863-10. 20 a. m.

Lieutenant-Colonel TAYLOR,

Chief of Staff, and Assistant Adjutant-General:

General Buford has started this morning with a very strong force to Culpeper, where be expects to find the enemy in force. I have sent out early this morning several detachments, in accordance with General Buford's request, to Thoroughfare Gap, Salem, and toward the Blue Ridge. Your order to send a strong reconnaissance into the Shenandoah Valley has just been received. I desire to know how strong a force you wish me to put forward into the Valley (my whole available force here in Fairfax is about 1, 000 men), or does the general commanding desire me to send out the reconnaissance from the force which I have on the Orange and Alexandria Railroad? This would leave the railroad, unprotected. It will also be necessary to keep a small force at this place, to protect my artillery. I am awaiting your orders.

I am, very respectfully, you obedient servant,

JUL. STAHEL,

Major-General Commanding.

[Indorsement.]

I have ordered a squadron sent from Fairfax Court-House.

S. P. HEINTZELMAN.

HEADQUARTERS, DEPARTMENT OF WASHINGTON,
June 6, 1863-11. 50 a. m.

Major-General STAHEL,

Commanding Cavalry, Department of Washington:

GENERAL: A strong squadron will be sufficient. I presume Buford will occupy fully all the available cavalry of the Confederates. Please keep us informed of anything of importance you may learn from Buford's movements.

J. H. TAYLOR,

Chief of Staff.