therefore, that you give me all the assistance you can with the mortars and gunboats. McArthur has been ordered to join McClernand, but I wish to countermand the order, if it has not already been executed. I have no means of communicating with General McArthur, except by way of Young's Point. Will you do me the favor to forward to him the accompanying?

U. S. GRANT,

P. S. - If the gunboats could come up and silence the upper water battery and clear the southern slope of the SECOND range of hills from the Yazoo Bottom, it would enable Sherman to carry that position, and virtually give us the city. The mortar-boats, I think, could be brought with security to within 1 mile or less of the bluff, on the Mississippi shore, from which they could rain shells into the city. Let me beg that every gunboat and every mortar be brought to bear upon the city.

FLAG-SHIP BLACK HAWK,

Near Vicksburg, May 22, 1863-Evening.

Major General U. S. GRANT,

Commanding Forces in Rear of Vicksburg:

DEAR GENERAL: I wrote to you to-day that we had commenced an attack with all the gunboats on the forts on the hills, which are silenced, and then proceeded to the water battery in front of the hospital, in hopes of silencing that. We found it a hard nut to crack, and fought it two hours, with apparently no damage to men, fort, or guns, which is not very strange, considering it stands back from the river, none of it is above ground, and we never saw a man. The vessels were a good deal cut up, but fortunately no one was killed. One of the hill batteries, after we had dismounted the gun, went to work to repair damages, and got a field piece in the fort, which we found out, and shelled the people away.

General McArthur's troops, which were landed at Warrenton this morning, went straggling along that way and were fired at by this field piece. It is a pity they did not assault, for they would have taken the place without any trouble, as there were not 20 men in it. It is the most important fort along that range of hills, commands the big rifle-gun fort, which we damaged and silenced, and the latter commands the rest of the batteries. I thought it would be well to let you know this, also that all the left of Vicksburg is open for the enemy to go out or in as he likes.

To day, before General McArthur came up, a large number of rebel cavalry went out, and a short time after a company of our cavalry came in, looking for Warrenton, and they never even met each other. McArthur has only 3,000 men; if he had 5,000, he could block up all that range of hills. If he will assault these forts, with the aid of the gunboats, he will taken them all. They are poorly manned; still, he must have ladders, as the ditches are deep. Our men are much used up, but we will bombard all we can. There is no danger of our firing into you, as we know exactly where you are. Most of our shell fall beyond the court-house, and none to the left of the fort, which General Sherman has been working at to-day.

Very respectfully,

DAVID D. PORTER.