ENGINEER BUREAU, Richmond, Va., October 11, 1862.

Major SAMUEL W. MELTON,

Assistant Adjutant-General, Richmond, Va.:

MAJOR: By direction of the Secretary of War I have assigned to Colonel Walter Gywnn, civil engineer, the duty of examining the Neuse, Tar, Roanoke, and Chowan Rivers, including their tributaries, with a view to their defense by obstructions placed in the rivers and batteries commanding the same. Colonel Gwynn is instructed to proceed with the works at once, if practicable. To aid him and give the necessary protection to his operations I have to respectfully request Major-General Smith, commanding, to give orders to the commanders in North Carolina and at Petersburg, Va., to act in concert with Colonel Gwynn, and afford him every assistance possible with the troops under their respective commands. I will, if possible, assign two engineer officers to assist in pressing forward the contemplated works. It is hoped the planters along the rivers will be able to furnish the requisite labor for constructing the defenses.

I am, very respectfully, &c.,

J. F. GILMER,

Lieutenant-Colonel and Chief of Bureau.

P. S.-Please furnish a copy of the general's orders to this Bureau for the use of Colonel Gwynn.

ENGINEER BUREAU,

Richmond, Va., October 11, 1862.

Captain C. R. COLLINS,

Corps of Engineers, C. S. Army, Smithville, N. C.:

CAPTAIN: Your letter of the 2nd instant was received three or four days ago, but a pressure of current business in this office has prevented an earlier reply. In reference to the construction of casemates in Fort Caswell I have to say that it is, in my judgment, impracticable to do so, but as a protection to the artillerists thick and high traverses should be constructed between the guns and the parapet raised on the right and left so as to form half embrasures, giving only such field of fire as may be necessary to cover the channels of approach. The parapet ought to have a height of not less than 5 1/2 even feet above the level of the terre-plein, and the intermediate traverses should have a thickness of not less than 18 feet at the base. If the guns are too near each other to allow space for traverses of the requisite dimensions then every alternate one should be removed and mounted at new points selected so as to give the best fire possible on the approaches. For rivetting the traverses the turf or sod from the low, marshy ground adjacent will probably answer, also for the increased height to be given to the parapet on the right and left of each gun. If possible, you should form bomb-proofs within the work for sheltering the artillerists not engaged in serving the guns. At the rear end and under the intermediate traverses may be a proper place for the bomb-proofs. If possible, additional long-range guns will be provided for Fort Caswell. As soon as the new appropriations become available funds will be placed to your credit, as promised by Captain Rives. It is out of the power of this Bureau, owing to the many calls for engineers, to furnish you with an assistant at this time. If the works will be delayed for the want of one you must employ a competent civil engineer.

Very respectfully, your obedient servant,

J. F. GILMER,

Lieutenant-Colonel and Chief of Engineer Bureau.