It is expected that General Banks will garrison Port Hudson with a few troops, and, with the remainder of his effective force, come up to co-operate in the reduction of Vicksburg. This will give us increased facilities for moving troops from New Carthage to Grand Gulf.

I wanted particularly to see you about the facilities for getting troops from Smith's plantation to New Carthage and the chances for embarking them; also to consult upon the probable effects of letting the water into the canal, upon the levees between Richmond and Carthage.

The water will be let in on Monday or Tuesday. You will want to have your men guard against all contingencies. As water is now flowing through the same channels, in great volume, from various crevasses, commencing just below the canal, I cannot see that this new cut is going to have much effect. We must be prepared for the effect, however, whatever it may be. I have been more troubled to know how to supply you with ammunition, until water communication is established, than on any other subject. If roads hold good, there will be no difficulty, but, without them, there will be. It is not safe to send by the river, as we do coal.

U. S. GRANT.

MEMPHIS, TENN., April 12, 1863.

Major General U. S. GRANT,

Commanding Department of the Tennessee:

GENERAL: The enemy are now running the railroad from Decatur to Tuscumbia, carrying off supplies to Johnston's [Bragg's?] army. Dodge informs me that he expects Rosecrans' force to show itself on the Tennessee about Wednesday next.

I have ordered the Seventh Kansas to move to-morrow to Corinth, supplying their place at Germantown with the NINTH Illinois. This will give Dodge the two most effective regiments of cavalry that I can furnish him (the Tenth Missouri and Seventh Kansas), and place the whole under command of Cornyn.

It is reported that pontoon bridges are in construction above Florence, and that the enemy's left in Middle Tennessee is heavily re-enforced with a strong massing of troops near Harpeth Shoals. This may hinder or delay Rosecrans' movement, in combination with which Dodge is to move; but whenever this movement does take place, which I think will be this week, the dash below will be attempted.

The withdrawal of the Yazoo Pass expedition will leave a force which I think will be used to re-enforce Chalmers at Panola,. If they really intend to move up. I am in doubt about this, but the balance of my judgment is that Chalmers is merely a cover for obtaining supplies.

I have delayed starting in the actual construction of the Memphis and Charleston Railroad until the front is thoroughly cleared; meanwhile am accumulating materials and supplies for the work at La Grange.

Lawler has come in from a ride with the Eighteenth Illinois, and reports 1 lieutenant-colonel, 2 captains, 3 lieutenants, and 38 privates prisoners. I regret to lose the Fifteenth Regulars from the fort, but must supply their place as best I can.

There is no news of any special import about this point, and all is quiet along the south of the line. It is currently believed below that the attack on Vicksburg will be abandoned.

A man from Port Hudson reports to me that they are preparing boats