Richmond. What would be gained by driving the enemy on either of those places? And if your detachment be not strong it would be lost. Hence the detachment, if not bad, would be useless. The enemy is concentrating upon Arlington and Alexandria, and this is the line first to be looked to. Is Wallace at Cumberland threatened from below? If so, the threatening detachment is cut off by your passage of the Potomac. McClellan has been told to-day to send nothing across the mountain to support you, as since the evacuation of Harper's Ferry you are strong enough without. The regulars with you are most needed here. Send them and the Rhode Islanders as fast as disengaged. Keep within the above limits until you can satisfy me that you ought to go beyond them. Report frequently.

WINFIELD SCOTT.

HEADQUARTERS DEPARTMENT OF PENNSYLVANIA,
Hagerstown, Md., June 16, 1861.

Bvt. Major General GEORGE CADWALADER,

Commanding First Division:

GENERAL: The commanding general wishes you to detach forthwith the whole of the Rhode Island regiment and battery, and send it immediately on receipt of this, with secret orders, to this place to march to Frederick, and there take rail for Washington City. Stop also the cavalry going towards Cumberland, and be ready to fall back to this bank of the Potomac. Orders will be sent to you to-morrow by noon.

By order of Major-General Patterson:

F. J. PORTER,

Assistant Adjutant-General.

HDQRS. DEPARTMENT NORTHEASTERN VIRGINIA,
Arlington, Va., June 17, 1861.

Lieutenant Colonel E. D. TOWNSEND,

Asst. Adjt. General, Hdqrs. of the Army, Washington, D. C.:

COLONEL: Brigadier-General Tyler, with part of the Connecticut regiment, made, agreeably to instructions, a reconnaissance up the Loudoun and Hampshire Road as far as Vienna. He found all the bridges and the road in good order. All the rolling stock of the road between Vienna and Leesburg he reports as having been burned, to prevent it falling into our hands. One of the sleepers, which had been set on fire by the droppings of the locomotive, gave rise to the report from the telegraph station near Arlington Mills that the bridges had been set on fire and were burning, and that General Tyler was beyond them.

Whilst near Falls Church one of the Connecticut regiment, Private George Bigbee, Captain Comstock's company, was wounded in the shoulder by a shot from the roadside. The man suspected of having fired it was captured, and is in jail in Alexandria.

It is reported re-enforcements have been sent from Manassas to Fairfax Court-House.

I have the honor to be, colonel, very respectfully, your most obedient servant,

IRVIN MCDOWELL,

Brigadier-General, Commanding.