I have directed Major Arnold to have four water batteries, mounting three guns each, to be erected on the adjacent keys. This being done, with the support of one or two ships of war, the whole anchorage will be within command of our guns.

I would respectfully recommend that at Fort Jefferson for the 42-pounders ordered 8-inch encumbered columbiads be substituted, and that the wooden carriages of all three forts be replaced at the earliest possible day by iron ones. I took from Fort Jefferson twenty negro laborers for the Engineer Department, thirty-one privates to fill up the companies, so that they are now full, a field battery and four mountain howitzers, with implements and ammunition, some bricks, and a large flat. We got under way at 8'clock p. m., and very soon lost the flat. Her lashing-rigs and hooks, not being sufficiently strong, drew out and left her adrift. Lieutenant McFarland and Reese, of the Engineers, on the advice of the chief engineer, have been attached to this command.

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

HARVEY BROWN,

Colonel, Commanding.

HEADQUARTERS DEPARTMENT OF FLORIDA,
Transport Steamship Atlantic, April 15, 1861.

Bvt. Major L. G. ARNOLD,

Commanding Fort Jefferson, Fla.:

MAJOR: My short stay at your post and the hurry of business prevented my conversing with you so freely as I could have wished on the defense of the fort. The importance of Fort Jefferson can hardly be overestimated, nor can I too strongly impress on you the importance of the constant exercise of every precaution and of the most unceasing vigilance against surprise. Your post may not improperly be considered the Gibraltar of America, and you should guard it with the same jealous vigilance you would if we were at war with a strong maritime power. No vessel, Government or merchant, should be allowed to approach without being boarded, and, if necessary, required to heave to for the purpose. Your guns should habitually be kept loaded and ready at a moment's notice to be fired; a sufficiency of ammunition always prepared for immediate service, and the officers and men assigned to their positions, so that by day or night each can at a moment's notice be at his post. Your drawbridge should always be raised at night, the embrasures closed and fastened, and the guards by day and night required to the observance of the greatest possible vigilance. The troops must be impressed with the necessity of almost constant fatigue in mounting us, erecting batteries, laying platforms, &c., and other necessary work, and encouraged to a cheerful compliance with the exigencies of the service.

I am aware, major, of your zeal and ability, and of the excellent discipline that has characterized your command, and I doubt not hat you will have anticipated these suggestions. If so, nor harm is done, and I wish, if any here made may have escaped you, that you will without delay given them your attention.

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

HARVEY BROWN,

Colonel, Commanding.