RICHMOND, July 6, 1861.

Honorable L. P. WALKER,

Secretary of War:

SIR: I take the liberty of calling your attention to the accompanying papers. Accompanying this letter you will find a copy of a plan for organizing secretly a military force for the liberation of the State of Maryland. There is also a copy of this plan in cipher. I inclose the key. Also a letter to the Honorable S. T. Wallis, of Baltimore, in cipher, and a copy. My object in presenting these papers to you is to ascertain the views of the War Department with regard to the proposed plan, and to request that, if it is possible, the letter and plan for Mr. Wallis may be sent to him as soon as possible. All correspondence may, if you desire it, pass through the Department, where it can be inspected. I will here state that if the plan succeeds, the moment the troops commence active service they will be prepared to enter the Confederate Army.

Hoping that you will give this matter your earliest attention, I have the honor to remain, very respectfully, your obedient servant,

JAMES D. McCABE, Jr.

[Inclosure Numbers 1.]

A plan for the effectual organization of a military force in the State of Maryland to co-operate with the Army of the Confederate States against the U. S. troops.

In order to assist the C. S. forces in their operations in Maryland it is proposed to organize, with the utmost secrecy, a force to co-operate with them at such time as the President of the Confederate States may designate. The organization is to be carried to perfection by appointing certain trustworthy persons in Maryland as officers, and authorizing them to enlist men and to them in readiness to concentrate at such points as shall be designated. The troops shall be armed with any weapons that are convenient to them. Shotguns, rifles, pistols, anything that is calculated to convey destruction to the enemy, may be used to advantage. In the country it may be possible to organize companies of cavalry, and it is desirable that as many may be formed as possible. The State is to be organized as one division, to be commanded by a major-general of division. It is to be subdivided into three brigades, each to be commanded by a brigadier-general. Each brigade is to consist of five regiments; each regiment of ten companies. The State is to be divided as follows:

First Brigade.-To comprise the following counties: Baltimore County (including the city), Harford County, Frederick County (including the city), Washington County, and Carroll County.

Second Brigade.-To comprise the following counties: Howard County, Anne Arundel County, Prince George's County, Calvert County, Charles County, and Saint Mary's County.

Third Brigade.-Cecil County, Kent County, Queen Anne's County, Talbot County, Dorchester County, Worcester County, Somerset County, and Caroline County.

The subdivision of brigades into regiments is as follows:

First Brigade.-First and Second Regiments, to be formed in Baltimore City; Third Regiment, to be formed in Baltimore City and County; Fourth Regiment, to be formed in Harford and Carroll Counties; Fifth Regiment, to be formed in Washington and Frederick Counties.