On James Island a party of fifty men are at work extending and enlarging the mortar battery at its right flank. This is evidently to be so enlarged and furnished with guns as to constitute the strong point on which rests the left flank of the line of entrenchments which covers Fort Johnson, and perhaps the city on that side. In this fort, the splinter-proof traverses being completed and the parade well cleared, the men are at work hosting to the terre-plein the 32-pounder chassis, to be used for temporary traverses between the guns.

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

J. G. FOSTER,

Captain of Engineers.

Numbers 89.] FORT SUMTER, S. C., March 31, 1861.

(Received A. G. O., April 4.)

Colonel L. THOMAS, Adjutant-General U. S. Army:

COLONEL: I have the honor to report that we do not see any work going on this morning. Yesterday, in consequence of the members of the Convention coming down, a great deal of firing of shot and shell took place at Fort Moultrie and from the batteries on Morris Island.

The three batteries outside of the Star of the West have certainly guns of very heavy caliber; this we know from the great extent of the ranges and from the reports.

As our provisions are very nearly exhausted, I have requested Captain Foster to discharge his laborers, retaining only enough for a boat's crew. I hope to get them off to-morrow. The last barrel of flour was issued day before yesterday.

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

ROBERT ANDERSON,

Major, First Artillery, Commanding.

FORT SUMTER, S. C., March 31, 1861.

General JOS. G. TOTTEN,

Chief Engineer U. S. Army, Washington, D. C.:

GENERAL: Yesterday the members of the State Convention visited the batteries on Morris Island and Fort Moultrie, and from both places extensive firing took place in honor of the event. This gave me an opportunity of observing what batteries have been increased in strength since my last report on this subject.

The following is the present armament very nearly, viz:

Battery Numbers 1.-Four guns. Embrasures closed by sand bags. Not fired yesterday.

Mortar battery between Nos. 1 and 2.-Three mortars. Fired yesterday. These have practiced much lately, to obtain the range and length of fuse for this fort.

Battery Numbers 2, iron-clad.-Three heavy guns. Two of them fired yesterday.

Battery Numbers 3.-Three guns. Embrasures closed with sand bags. Did not fire.

Mortar battery between Nos. 3 and 4.-Two mortars. Fired yesterday.

Battery Numbers 4.-Three guns. Two fired.

Battery Numbers 5.-Four heavy guns, one columbiad or 8-inch sea-coast