HEADQUARTERS DEPARTMENT OF PENNSYLVANIA,
Chambersburg, Pa., June 14, 1861.

Colonel CHARLES P. STONE,

Commanding, near Leesburg, Va.:

SIR: The commanding general instructs me to inform you that as soon as he can move his force, so as to strike a blow on the enemy's left, at Harper's Ferry, and follow it up with success, he will inform you, to obtain your co-operation, if circumstances, in your judgment, will permit. He desires to be informed of your position, and whether you can most advantageously threaten the Maryland or Virginia Heights opposite Harper's Ferry. He will not necessarily rely upon your cooperation, though glad to receive it. Can you stop supplies passing from Frederick County, Maryland, into Harper's Ferry?

I am, sir, very respectfully, your obedient servant,

F. J. PORTER,

Assistant Adjutant-General.

CHAMBERSBURG, PA., June 14, 1861.

Brevet Major General GEORGE CADWALADER,

Commanding First Division, Greencastle, Pa.:

GENERAL: The commanding general desires me to inform you that in operating against the forces which occupy and surround Harper's Ferry his design is, in general terms, as follows:

First. To threaten an attack of the Maryland Heights.

Second. To turn the enemy by their left, through or near Martinsburg, with a strong column of mixed arms of service (cavalry mainly in reserve for critical moments, either to launch upon the enemy, to sustain our columns, or hasten the movements of a retreating enemy), cut their line of communication, and attack them in position.

Third. To sustain the advance column by a force strong enough to resist an effort to cut off the advance, maintain the line of communication, and give the necessary aid to sustain the movement.

A reconnaissance of the enemy's position may cause a change in this plan, but it is not likely to any material degree. The commanding general, therefore, desires you, while he is preparing his forces, to mature your plans for executing so much of the design as will fall to the lot of your division, that of taking the advance and breaking the enemy's lines. The commanding general has every reason to believe that a determined stand will be made at Harper's Ferry-a desperate struggle for supremacy; and so momentous are the interests of our country, involved in the undoubted success of our arms, that all plans must be matured with great prudence; the agents selected and so well disciplined as to render victory certain. While in position near Williamsport, the sustaining force being unprepared, the commanding general desires you to avoid bringing on a collision of any extent by entering Virginia, or attempting anything the success of which is doubtful. Many efforts will be made to induce you to cross the river, but heed them not or give them your careful consideration, and, whatever you undertake, move with great caution. When our forces cross the river he does not wish to withdraw, but to be able to sustain them and to advance. This, of course, is not designed to restrict you in regard to parties who may annoy you or be destroying property or the dams or cross the river into Maryland. They must be quickly met by an overpowering force.