Ten o'clock came, the hour for divine service. The church flag was flung out on the flagstaff of the Benton, and all the commanders called their crews together for worship. I was on board the Pittsburg with Captain Thompson. The crew assembled on the upper deck. There were men from Maine, New Hampshire, Massachusetts, and Rhode Island, from the Eastern as well as the Western States. Some of them were scholars and teachers in Sabbath-schools at home. They were dressed in dark-blue, and each sailor appeared in his Sunday suit. A small table was brought up from the cabin, and the flag of our country spread upon it. A Bible was brought. We stood around the captain with uncovered heads, while he read the twenty-seventh Psalm. Beautiful and appropriate was that service:-- "The Lord is my light and my salvation; whom shall I fear? The Lord is the strength of my life; of whom shall I be afraid?" After the Psalm, the prayer, "Our Father which art in heaven." How impressive! The uncovered group standing around the open Bible, and the low voices of a hundred men in prayer. On our right hand, looking down the mighty river, were the mortars, in play, jarring the earth with their heavy thunders. The shells were sweeping in graceful curves through the air. Upon our left hand, the Benton and Carondelet were covering themselves with white clouds, which slowly floated away over the woodlands, fragrant with the early buds and blossoms of spring. The Rebel batteries below us were flaming and smoking. Solid shot screamed past us, shells exploded above us. Away beyond the island, beyond the dark-green of the forest, rose the cloud of another bombardment, where Commodore Hollins was vainly endeavoring to drive Colonel Plummer from his position. So the prayer was mingled with the deep, wild thunders of the cannonade. A light fog, like a thin veil, lay along the river. After service, we saw that strange and peculiar optical illusion called _mirage_, so often seen in deserts, where the thirsty traveller beholds lakes, and shady places, cities, towns, and ships. I was looking up stream, and saw, sweeping round the wooded point of land, something afloat. A boat or floating battery it seemed to be. There were chimneys, a flagstaff, a porthole. It was seemingly two hundred feet long, coming broadside towards us. "Captain Thompson, see there!" He looked at it, and jumped upon the pilot-house, scanned it over and over. The other officers raised their glasses. "It looks like a floating battery!" said one. "There is a porthole, certainly!" said another. It came nearer. Its proportions increased. "Pilot, put on steam! Head her up stream!" said Captain Thompson. "Lieutenant, beat to quarters! Light up the magazine! We will see what she is made of." There was activity on deck. The guns were run out, shot and shell were brought up. The boat moved up stream. Broadside upon us came the unknown craft.