The work that I spoke of in my last letter as being commenced upon the middle of the curtain, connecting the first breaching battery and the second, has not sufficiently developed itself to be positive in its character, but it appears to be a large magazine and a battery for three or more guns. A considerable force is also at work on that portion of the field work looking towards Fort Moultrie and the channel, but I cannot see what is being done. I have no doubt that it is the construction of one or more embrasures, in addition to the one there before, to fire on the channel. The floating raft intended to be used to breath the walls of this fort was launched yesterday in town. I can see it with my glass. The iron does not appear to have been yet put upon the timber. If I am correct in this, it will require several days to prepare it for action.

Yesterday I was principally employed in demolishing the temporary building for fuel, removing materials, &c., of blacksmith shop to the casemates, clearing the parade, &c.

I have strongly recommended the increasing of the present armament of the gorge [six 24-pounders] at once, by means of the casemate carriages, so altered as to answer for barbette carriages, but the recommendation has not yet been acted on.

I did not write to the Department yesterday morning, having been closely employed until it was too late to do so before the mail closed.

Very respectfully, your obedient servant,

J. G. FOSTER,

Captain of Engineers.

No. 59.] FORT SUMTER, S. C., March 1, 1861.

Colonel S. COOPER,

Adjutant-General U. S. Army:

COLONEL: I have the honor to report that nothing unusual occurred to-day, except the arrival from the city of a steamboat, fully loaded with troops, at Sullivan's Island. The works around us are being carried on with the same activity as heretofore. Yesterday some guns were fired from a battery on Sullivan's Island to the eastward of the Moultrie House.

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

ROBERT ANDERSON,

Major, First Artillery, Commanding.

FORT SUMTER, S. C., March 1, 1861.

General JOS. G. TOTTEN,

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

GENERAL: I have the honor to report that nothing of importance connected with the hostile batteries around us has transpired since I wrote yesterday. The work then in progress on the batteries on Cummings Point has continued steadily, but without any marked activity; the fourth embrasure in battery No. 3 [breaching] is reverted and the parapet nearly finished; the work on the curtain of 1 and 2 is either a magazine or a bomb-proof of timber to be used as a battery, like battery No. 2. Little of note is observed at Fort Moultrie. The large bag of cotton or wool still remains in each embrasure precisely as it was placed some time ago, which makes me now believe that the guns on the face have really been dismounted to be used in other batteries.