*MAP.

howitzer. Two fired yesterday. I think there are six guns in this battery, although only four have been seen to fire.

Star of the West battery.-Four heavy guns, one of them an 8-inch columbiad or 8-inch sea-coast howitzer. All fired yesterday.

Battery Numbers 7.-These guns are not all in the same battery, but are distributed along the beach apparently in three batteries. Eleven guns fired yesterday. All were very heavy guns except two, which I think were field pieces in a sort of second tier at a and b.

Above these batteries, on the sand hills, is a line of entrenchments surrounding a house, and also several tents. The field pieces are apparently at a and b, capable of being used to defend the flanks of this entrenchment, and to fire on the channel. Their rear is covered, each with a traverse.

It was evident in this firing that not all the guns in position were fired.

At Fort Moultrie the firing exhibited the same complete armament as last reported.

The provisions that I laid in for my force having become exhausted, and the supplies of the command being too limited to spare me any more, I am obliged to discharge nearly all my men to-day. I retain only enough to man a boat.

I have the honor to be, very respectfully, your obedient servant,

J. G. FOSTER,

Captain, Engineers.

NAVY DEPARTMENT, Washington, April 1, 1861.

To the COMMANDANT OF THE NAVY-YARD, Brooklyn N. Y.:

Fit out the Powhatan to go to sea at the earliest possible moment under sealed orders. Orders by a confidential messenger go forward to-morrow.

ABRAHAM LINCOLN.