HEADQUARTERS THIRTEENTH ARMY CORPS, Willow Springs, MISS., May 6, 1863.

Major General U. S. GRANT, Comdg. Dept. of the Tennessee:

GENERAL: Colonel Taggart, chief commissary Thirteenth Army Corps, calls to see you this morning. His object is to get an order placing a hundred wagons of the SEVENTEENTH Army Corps, or any wagons, at his disposal, for the purpose of bringing rations to the men of the Thirteenth Army Corps. He will explain the necessity for it.

General Osterhaus reports that he learns that the main force of the enemy on the east of Big Black has returned to Edwards Station, on the railroad and east of the Big Black. The detachment encountered by General Osterhaus yesterday was a corps of observation sent out to watch our approach. The cavalry with General Osterhaus is now occupying all the roads northeast and south of the cross-roads near Cayuga Reconnoitering parties have been sent from the same vicinity toward Utica and Gallatin. A corps of observation has been sent out toward Edwards Station, while still another party has been sent up the river in pursuit of the rebel steamers.

Respectfully, your obedient servant,
JOHN A. McClernand.

CAMP OPPOSITE GRAND GULF, May 6, 1863-12 m.

Major-General BLAIR:

DEAR GENERAL: I sent your orders to follow us, leaving two regiments at Richmond and two a Milliken's Bend, to be relieved by others from Memphis, when these regiments are to follow and overtake us. General Grant has ordered one brigade of McArthur's DIVISION, also, to remain, and the other to join him. The steamboats here are poor concerns, except the Forest Queen, and the ferrying across will be a slow process. I would not be surprised if you would overhaul us before we are all across.

General Grant wants the commanding officer at Milliken's Bend, General Sullivan, I suppose, to call in all the troops on this road, and occupy the road from my old headquarters to a point below Warrenton. The road will need a good deal of work. You may send in to Milliken's Bend all at Richmond, and see that al detachments of my corps either keep along ahead of you, or return to Milliken's Bend, to be put on that road.

Steamboats, after passing us over to Grand Gulf, will run up to get supplies there, viz, on the WEST bank, below Warrenton. You will find plenty of forage along this road, especially this end of it, viz, from Perkin's to Hard Times. Your map is correct as far as Perkin's place which is at the lower end of Bayou Vidal. From Perkin's to this point the road is well marched, following Lake Saint Joseph, along which you will find some magnificent plantations. At Dr. Bowers' you can send across the lake in a boat, and procure plenty of beef, hogs, and sheep. Corn is to be found in all the stables, and from Dr. Bowers' to this place there is growing wheat, oats, and corn, on which you can feed your horses. The whole distance from Milliken's Bend to Hard Times plantation is 63 miles; road cannot be mistaken; better at this end than at yours.

Steele overtook his command, and rode in about an hour ago, and has gone back a mile or so to give the necessary orders for embarkation. I will cross over to-night, and will try and send you back all possible