After the capture of Alexandria and the dispersal of the enemy in that quarter, General Banks moved down with his army to Simmesport, on the Atchafalaya Bayou, five miles from the Red River, and thence across the Mississippi at Bayou Sara, five or six miles above Port Hudson. General Augur of his command at the same time moved up from Baton Rouge. The two bodies met on the 23d of May, and Port Hudson was immediately invested. An assault was made on the 27th, but proved unsuccessful, and the army settled down to a regular siege. A battery of four IX-inch shell-guns from the navy was efficiently served throughout the siege by a detachment of seamen from the Richmond and Essex under Lieutenant-Commander Edward Terry, executive officer of the former vessel. The Essex, Commander Caldwell, and the half dozen mortar-schooners under his orders maintained a constant bombardment and succession of artillery fights with the river batteries of the enemy, being exposed to the fire of four VIII-and X-inch columbiads and two heavy rifles. Between the 23d of May and 26th of June Caldwell estimated that one thousand shot and shell had been fired at him from these guns. During these daily engagements the Essex was hulled twenty-three times, besides being frequently struck above her decks, and had received severe injury. The mortar-schooners also came in for their share of hard knocks, and their captains were all specially commended both by Caldwell and Farragut. On the 15th of May Porter went to the Yazoo and there awaited news from the army. On the 18th heavy firing in the rear of the city assured him of Grant's approach. That afternoon the advance of Sherman's corps came in below Snyder's Bluff, between the city and Haines's Bluff. The works at the latter point had been abandoned the evening before on the approach of the army; a small party only being left to destroy or remove whatever they could. Upon the appearance of the troops the admiral sent up a force of gunboats under Lieutenant-Commander K.R. Breese, whereupon the party ran off, leaving everything in good order. The works mounted fourteen heavy guns, VIII-and X-inch smooth-bores, and VII1/2-inch rifles; the carriages of these were burned, as were the Confederate encampments, and the magazines blown up. Porter now received letters from Grant, Sherman, and Steele, informing him of the entire success of the campaign in the rear of Vicksburg, and asking that provisions might be sent up, the army having lived off the country almost entirely during a fortnight of constant marching and fighting. Lieutenant-Commander J.G. Walker in the De Kalb was sent up to Yazoo City with sufficient force to destroy the enemy's property which he might find, and the gunboats below Vicksburg were moved up to fire on the hill batteries, an annoyance to the garrison which they kept up off and on during the night. On the 19th six mortar-boats were got into position, with orders to fire night and day as rapidly as possible.