MEMPHIS, Tenn., April 26, 1863.

Lieutenant Colonel John A. RAWLINS, Asst. Adjt. General, Dept. of Tennessee:

SIR: I learn from Dodge that he occupied Tuscumbia on 24th, and proposed to take Florence on 25th. Quite a brisk skirmish on Little Bear Creek. Loss not reported, if any. Johnston sent word to troops at Tuscumbia that he could not re-enforce. Great consternation from the belief that Dodge is the head of a column to attack Johnston in flank and rear.

Colonel Streight pushes out to-day on his trip. Dodge feels confident of his position.

The column under General Smith dispersed Chalmers, capturing many small-arms, principally shot-guns, 230 horses and mules, and a number of wagons of provisions and supplies. Our troops are now all at their stations. Nothing further from Grierson.

The SECOND Iowa Cavalry is reported to have destroyed barracks, stores, and railroad at Okolona and Tupelo and at other points. They are not in yet, and may have some trouble, but Hatch will take care of himself and his men. Everything, so far as I can learn, is moving well on this line, though Chalmers may make a dash to pass our railroad or capture a train. The men are in splendid health. Hospitals much reduced, and room enough for patients from below.

Your obedient servant,

S. A. HURLBUT.

PERKINS' PLANTATION, La., April 27, 1863.

Major General John A. McClernand, Comdg. Thirteenth Army Corps:

Commence immediately the embarkation of your corps, or so much of it as there is transportation for. Have put aboard the artillery and every article authorized in orders limiting baggage, except the men, and hold them in readiness, with their places assigned, to be moved at a moment's warning. All the troops you may have, except those ordered to remain behind, send to a point nearly opposite Grand Gulf, where, you will see by Special Orders of this date, General McPherson is ordered to send one DIVISION.

The plan of the attack will be for the navy to attack and silence all the batteries commanding the river. Your corps will be on the river, ready to run to and debark on the nearest eligible land below the promontory first brought to view passing down the river. Once on shore, have each commander instructed beforehand to form his men the best the ground will admit of, and take possession of the most commanding points, but avoid separating your command so that it cannot support itself. The first object is to get a foothold where our troops can maintain themselves until such time as preparations themselves until such time as preparations can be made and troops collected for a forward movement.

Admiral Porter has proposed to plache position indicated to you a few days ago, and to bring over with them such troops as may be below the city after the guns of the enemy are silenced.

It may be that the enemy will occupy [such] positions back from the city, out of range of the gunboats, as to make it desirable to run past Grand Gulf and land at Rodney. In case this should prove the plan, a signal will be arranged, and you duly informed when the transports are to start with this view. Or it may expedient for the boats to run past, but not the men. In this case, then, the transports would have to be brought back to where the men could land, and move by forced marches