Numbers 15.] FORT SUMTER, S. C., December 31, 1860.

(Received, A. G. O., January 5, 1861.)

Colonel S. COOPER, Adjutant-General:

COLONEL: I have the honor to report that the South Carolinians show great activity in the harbor to-day. Several steamers have been running to and for, and this afternoon about 80 soldiers, with wheel-barrows, barrels, &c., and some draught horses, were landed on Morris Island. They are evidently constructing a battery or batteries there. The lights in the harbor were put out last night, and ours is the only light-house of this harbor which exhibits a light to-night. I am not a loss what this means, unless it be that some armed vessel is expected here. The more I reflect upon the matter the stronger are my convictions that I was right in coming here. Whilst we were at Fort Moultrie our safety depended on their forbearance. A false telegram might, any night, have been seized upon as an excuse for taking this place, and then we would have ben in their power. And even if there had been an understanding between the two Governments that I was not to be interfered with until the termination of the mission to Washington, the fact of the governor's having ordered armed steamers to keep watch over me would have absolved our Government from the obligation to remain quiescent. It is certain, too, that the moment a telegram was received announcing the failure of the mission, an attack would have been made and my command sacrificed, for there can be no surrender with these men,if attacked, without a serious fight. Thank God, we are now where the Government may send us additional troops at its leisure. To be sure, the uncivil and uncourteous action of the governor in preventing us from purchasing anything in the city will annoy and inconvenience us somewhat; still, we are safe. I find that in consequence, of a failure (accidental) to comply with my instructions, there is only a small supply of soap and candles, and also of coal. Still, we can cheerfully put up with the inconvenience of doing without them, for the satisfaction we feel in the knowledge that we can command this harbor as long as our Government wishes to keep it.

I am, colonel, respectfully, your obedient servant,

ROBERT ANDERSON,

Major, First Artillery, Commanding.

Reply of Commissioners to the President.

WASHINGTON, D. C., January 1, 1861.

To his Excellency the PRESIDENT OF THE UNITED STATES:

SIR: We have the honor to acknowledge the receipt of your letter of the 30th December in reply to a note addressed by us to you on the 28th of the same month, as Commissioners from South Carolina.

In reference to the declaration with which your reply commences, that "your position as President of the United States was clearly defined in the message to Congress of the 3rd instant," that you possess "no power to change the relations heretofore existing," between South Carolina and the United States, "much less to acknowledge the independence of that State," and that, consequently, you could meet us only as private gentlemen of the highest character, with an entire willingness to communicate to Congress any proposition we might have to make, we deem it only necessary to say that the State of South Carolina having, in the