be obstructed by crib-work sunk with brickbats and sand. Iron-plated ships detained by such obstacles would probably be destroyed by columbiads.

Fort Gaines, though far from a completed state, is capable of receiving its armament. We have already mounted ten 32-pounders and have received two 10-inch columbiads, but no carriges for them. Three more columbiads are absolutely necessary, one for each bastion, and carriages are quite as important as guns. The bastions and traverse circles are ready for the columbiads. Twenty 24-pounder howitzers are necessary for flanking the ditches, and I hear nothing of them. Additional guns to the number of forty are wanted here to arm batteries guarding the island against an enemy's landing out of range of the fort. The present garrison is about 400, and should be increased to 1,000 for the fort and batteries. Grant's Pass is tolerably well defended by three 32-pounders, but the addition of an 8-inch columbiad would be advisable.

Against the gun-boats which the enemy will bring next fall I can hardly conceive that we shall be prepared to hold Mississippi Sound, and in case of disaster to our forces in that quarter Mobile will be open to land attack by way of Pascagoula, Portersville, &c. The intervening country can be made available for a good defense, but I fear that our preparations might be inabequate, and our positions might be turned, if not forced. A position prepared beforehand in front of the city - a semicircle of batteries half a mile a Part and connected by curtains for musketry - would be far less liable to danger. They should extend from Choctaw Point along the bay shore to about the two and one-quarter mile circle (from the court-house), and following that circle nearly to Three-Mile Creek, should end a at the mouth of One-Mile Creek, above the city. The battery at Choctaw Point, in conjunction with another at or near the mouth of Spanish River, would cover every channel of more than four feet deep leading up the river. The land batteries at the city would not be elaborate or expensive. They would consist of a parapet embanked on the natural soil, with a reverse glacis in front, covering an abatis. They would give shelter to the men and guns, and afford every facility for an advantageous battle. Probably fourteen such batteries would be needed. Such preparations as have been suggested would cost some money, especially the closing or obstructing the channel at Fort Morgan. But we must, if necessary, spend our all in this business, certainly hundreds of millions, and I know of no point more worthy the application of a half of one million that Mobile Bay. True economy of money and of life would be consulted by making an attack hopeless. There should be no joint in the armor which covers our vitals. I am not tenacious of details, but if this system or its equivalent be not undertaken and carried out promptly Mobile is in danger. The victory at Manassas was stupendous.

Very truly, sir, your obedient servant,

D. LEADBETTER,

Major of Engineers.

[6.]

UNION CITY, August 5, 1861.

Major General L. POLK, Memphis:

GENERAL: By telegraph to-day I ordered the South Carolina, Alabama, and Louisiana companies from Corinth to Memphis. As I had ordered them to leave Corinth for this post to-day at 12 m., I doubt not they were ready and their destination changed by your wishers, as I at the same time telegraphed the agent of the Memphis and Charleston Railroad to send to you without delay. I hope you will have