Grand Gulf will be struck before the canal is finished and its utility decided by experiment. Admiral Porter is ready and anxious to go forward, but I presume the more cautious course will be chosen. The attack on Grand Gulf will be led by McClernand, and though General Grant has not told me so, I conclude he intends the same officer to have command of the further movement against Port Hudson. I have remonstrated, so far as I could properly do so, against intrusting so momentous an operation to McClernand, and I know that Admiral Porter and prominent members of his staff have done the same, but General Grant will not be changed. McClernand is exceedingly desirous of this command. He is the senior of the other corps commanders. He is believed to be an especial favorite of the President, and the position which his corps occupied on the ground here when this movement was first projected was such that the advance naturally fell to its lot; besides, he entered zealously into the plan from the first, while Sherman doubted and criticized, and McPherson, whom General Grant would really much prefer, is away at Lake Providence; and though I understand him to approve of the scheme, he has had no active part in it. It is estimated that 10,000 men can take Grand Gulf, fortify it, and hold it, and at the same time make any necessary feints up the shore of the Big Black, while 20,000 more go down to Port Hudson. In this operation McClernand and McPherson will both be engaged, while Sherman will remain to menace Vicksburg from here and guard the line of communications. McPherson's troops have been ordered here for the movement. F. Steele reports from Greenville that he has taken 2,000 head of cattle and great numbers of negroes, and destroyed enormous quantities of forage that he could not remove. He pursued S. W. Ferguson as far as he dared. General [Lorenzo] Thomas arrived here yesterday. He is quite ILL with the diarrhea, but isning.

C. A. DANA.

Honorable E. M. STANTON,

Secretary of War.

MILLEKEN'S BEND, April 14, 1863,

VIA MEMPHIS, April 23.

Colonel G. G. Pride let the water into his canal at 12 m. yesterday. The channel is now full, and there is no reason to doubt its usefulness. The dredges have been at work deepening it all to-day. Major W. Tweeddale, who was sent with a working party to clear out the trees from the bayou, reports that all is done to within 5 miles of Richmond, but that the remaining distance is much more obstructed than the rest of the line, so that four days at least will be required to open the passage for tugs and barges. From Richmond to New Carthage the way is believed to be clear, through it is not yet settled whether opening this canal will overflow the road. He thinks no overflow will occur. Osterhaus' DIVISION has been at New Carthage for ten days; A. J. Smith's DIVISION is under orders to march to-morrow, and Hovey follows immediately, all under McClernand. The camp equipage of the army corps is to be sent down in four barges along with Admiral Porter's gunboats, which are intended to run the batteries to-morrow night, taking with them three transports. Having passed the batteries, the transports Grand Gulf before it can be re-enforced. The transports and barges will at once return for more troops, and as soon as the whole