JACKSON, May 11, 1863.

Lieutenant-Colonel BINMORE, assistant Adjutant-GENERAL:

The following dispatch just received from General Dodge:

The First Alabama Cavalry have returned from their trip to Monroe and Fayette Counties, Alabama. They bring in several prisoners; one of whom says Streight was captured by combined forces of Roddey and Forrest and Walker, beyond Clintonville, going in direction of Rome, Ga. They cannot give time or place. I know that Roddey attacked Streight and took pieces of artillery. Report since this that Forrest attacked the next night (midnight), and after, by their prisoners' report the three captured him. One thing is certain, Roddey and Forrest are not now following him. Scouts say that the rebels believe that an expedition is being sent south from here, and have sent two regiments and two battalions and Roddey's command and five regiments of Forrest's command, all under command of Roddey, south, on the Cotton-gin road. The men say they are to operate in the ear of my force that leaves here. Van Dorn is also reported killed, by a citizen. Forrest gone to Tennessee to take command. There is no doubt that several mounted regiments have been down the Cotton-gin road. The Alabamians ran across some of them, and a pretty large force is concentrated at and about Okolona. I will not be surprised if they intend a raid on our communications.

G. M. DODGE.

R. J. OGLESBY.

HDQRS. DEPT. OF THE GULF, NINETEENTH ARMY CORPS, Alexandria, La., May 12, 1863-8 a. m.

Major-General GRANT, Comdg. Forces before Vicksburg:

GENERAL: Your dispatch of the 10th instant I received by the hand of Captain [H. A.] Ulffers this morning at 6. 30. I regret to say that it is impossible for me to join you at Vicksburg in time or with force to be of service to you in any immediate attack. I have neither water nor land transportation to make the movement by the river or by land. The utmost I can accomplish is to cross for the purpose of operating with you against Port Hudson. I could cross my infantry and artillery without transportation, receiving supplies from Baton Rouge, in the rear of Port Hudson. That is the utmost I can accomplish on the other side of the Mississippi above Port Hudson. Were it within the range of human power, I should join you, for I am dying with a kind of vanishing hope to see two armies acting together against the strong places of the enemy. But I must say, without qualification, that the means at my dispose do not me a shadow of a chance to accomplish it. I have been making preparations to join your corps at Bayou Sara, and though this would have laid all my trains and supplies open to the enemy's cavalry, I should have risked it.

We believe that a force of about 7,000 of the enemy has left Arkansas River to join Kirby Smith at Shreveport, leaving the Washita at Pine Bluff, near Monroe; then to come down the Red River to Grand Ecore, above Natchitoches, where they are fortifying in strong position. There is undoubtedly a Texan on the road to join them. My advance is now 60 miles above Alexandria. The only course for me, failing in co-operation with you, is to regain the Mississippi and attack Port Hudson, or to move against the enemy at Shreveport. Port Hudson is reduced in force, but not as you are informed. It has now 10,000 men, and is very strongly fortified. This is the report of Admiral Farragut, whose fleet is above and below the works.

I regret very much my inability to join you. I have written Colonel Grierson that you desire him to join you, and have added my own request to yours. Captain Ulffers goes to Baton Rouge to communicate with him.