HEADQUARTERS FIFTEENTH ARMY CORPS,
Napoleon, Ark., January 16, 1863.

Major A. SCHWARTZ,

Assistant Adjutant-General to General McClernand:

SIR: My corps is now all assembled here with the exception of one boat, the Spread Eagle, which I hard of the mouth of White River, but which must learn there of their mistake easily by coming down the main river; also the Omaha with the Fifty-seventh Ohio, Colonel Mungen, which I detached yesterday morning to report to General Mcclernand, according to your orders.

Five boats arrived from Memphis this afternoon containing a small brigade commanded by Brigadier-General Ewing, which was detached from Western Virginia for General Rosecrans but sent to us on receipt of the intelligence that Rosecrans had repulsed Bragg and that we on the Mississippi needed re-enforcements. Brigadier-General Ewing brings orders, of which the following is a copy:

SPECIAL ORDERS, HEADQUARTERS DEPARTMENT OF THE TENNESSEE,

Numbers 12. Memphis, January 12, 1863.

X. Brigadier-General Ewing's brigade, now under orders to join the Mississippi expedition, is hereby assigned to Brigadier General Morgan L. Smith's division, of the Fifteenth Army Corps, and will report accordingly.

By order of Major-General Grant:

JNO. A. RAWLING,

Assistant Adjutant-General.

This gives three brigades to each of my two divisions and gives me an effective force of 15,909 men.

Three of A. J. Smith boats are here, who have reported they were ordered to follow certain boats, one of which had been dispatched down.

My orders state "Morgan's corps will follow to some point (Napoleon) as soon as practicable." I have not ordered in case of these boats, but merely mentioned to the commanders that I believe Morgan would follow. If you want them up at the Post send me word and I will dispatch them. On your way down you will find wood and rails near the cut-off and some fine cribs of corn a short distance above. I send for the general some late papers and invite his attention to the Memphis Bulletin of the 10th instant. He will see our success at Post Arkansas recorded, and also the fact that the rebels are investing Spring-field, Mo., and threatening Lexington. The report I received of acting Brigadier-General Garland that Herron and Blunt had retreated from Van Buren must be correct, and his may be additional reason why we should make some move up the Arkansas. The Mississippi River is reported to have fallen slightly, but it looks to me full and high here; but we had not a particle of difficultly in descending.

Napoleon is a hard-looking place, and I can see no place where I could form a brigade. I doubt if we can do much in the way of drill or discipline anywhere whilst we are afloat, but I will continue to try.

My chief object in sending a boat up to the general is to send him the newspapers, which five full accounts of Rosecrans' battle. Bragg retreats in the direction of Chattanooga. Grant is in Memphis. Nothing doing on the Rappahannock, and accounts from rebel sources that Banks approaches Port Hudson.

I am, with great respect, your obedient servant,

W. T. SHERMAN,

Major-General, Commanding Corps.