Fourth Iowa Cavalry, now here. The FIFTH Illinois is armed with carbines, and also the detachment of the SECOND Illinois, now here. This gives about 1,200 well-armed cavalry. Colonel Johnston believes, with this force, properly supported with infantry and artillery, he can destroy the railroad bridge over the Big Black north of Canton. The plan is to move the whole cavalry force toward Mechanicsburg to-morrow morning by the three roads I pointed out to you, the main body moving by the central road, with flanking parties on the right and left hand roads, and at the same time to send Mower's brigade, with a full battery of artillery, by the Yazoo River to Satartia, to land at that point and push to Mechanicsburg. This will compel [W.] Adams' cavalry, the only force on this side of Black River, to cross the Big Black River at Kibby's or Cox's Ferry in order to escape capture, and prevent them from recrossing that river, while Johnson with his entire force can push forward and destroy the bridge with little risk or hazard; nor will Mower's brigade, provided with transports at Satartia convoyed by a gunboat, run any risk, especially if he keep out a few cavalry on the different roads to advise him of the enemy's movements. As for the cavalry force of Johnson, it cannot be endangered, as there are so many roads by which he can retreat, and the enemy having no cavalry force sufficient to cut him off from all of them.

I think this plan is judicious and feasible, and, if you will permit it, I will issue the necessary orders, and leave one brigade of troops at this point of greater security during the absence of Mower's brigade, and with the balance of my command return to your lines in rear of Vicksburg to-morrow. It will be necessary to send Mower the other two sections of Spoor's battery (Iowa battery), of which he now has one, or I can give him a full battery from those now with me. I respectfully submit this plan and await your decision.

Respectfully,

FRANK P. BLAIR,

[Indorsement.]

HEADQUARTERS DEPARTMENT OF THE TENNESSEE,
In the Field, near Vicksburg, June 2, 1863.

Respectfully returned to Major-General Blair, commanding Expeditionary Corps, who will issue orders for the expedition against the Big Black railroad bridge north of Canton, in exact accordance with the plan within proposed. He will send one of the batteries he has with him with the expedition against there Big Black railroad bridge north of Canton, in exact accordance with the plan within proposed. He will send one of the batteries he has with him with the expedition in place of Spoor's, which latter he can get when he returns here. Colonel Richmond's brigade has been ordered to debark at Haynes' Bluff immediately, and will form the garrison at that place.

By order of Major General U. S. GRANT:

JNO. A. RAWLINS,

Assistant Adjutant-General

NEAR Vicksburg, MISS., June 2, 1863.

Rear-Admiral DAVID D. PORTER,

Commanding Mississippi Squadron:

The expedition under General Blair has clearly ascertained the fact that Joe Johnston is collecting an army at and around Canton, MISS., They find also there is a good ridge road leading between the Big