The fleet and batteries exchanged fire with greater or less severity every day. On the 21st, another large gun, called the Belmont, burst on the island. In the course of these engagements the redan was finally knocked to pieces and ceased to reply; and, on April 1st, an expedition from the fleet landed, drove off a detachment of the First Alabama which was guarding it, and spiked its guns. The work of erecting new batteries and mounting guns, as well as repairing damages, was continued as long as the island was occupied.

On the night of March 17th, General McCown left for Fort Pillow with the Eleventh, Twelfth, and Colonel Kennedy's Louisiana, Fourth, Fifth, and Thirty-first Tennessee, Bankhead's and six guns of Captain R.C. Stewart's batteries, and Neely's and Haywood's cavalry, leaving at Madrid Bend the First Alabama, Eleventh and Twelfth Arkansas, and Terry's Arkansas Battalion, three Tennessee regiments, commanded respectively by Colonels Brown, Clark, and Henderson, Colonel Baker's regiment of twelve companies called the Tennessee, Alabama, and Mississippi regiment, five guns of Captain Stewart's field-battery, and Captain Hudson's and Captain Wheeler's cavalry. Besides these were the companies of heavy artillery, and what other troops, on the island and below, the reports do not show. Most, if not all of the troops taken to Fort Pillow by General McCown, proceeded to Corinth and joined the force which General A. S. Johnston was gathering there. General McCown on his return arrived below Tiptonville on March 20th, and established his headquarters at Madrid Bend next day.

General Pope had now established his army and batteries on the right bank of the river, so as to prevent the escape of the enemy until the river should fall. To capture them he must cross the river. General Halleck telegraphed to him on March 16th to construct a road, if possible, through the swamp above the bayou, which comes into the river just above New Madrid, to a point on the Missouri shore opposite Island No. Ten, and transfer thither enough of his force to erect batteries and aid the fleet in the bombardment of the island. Pope despatched Colonel Bissell to examine the country with this view, directing him at the same time, if he found it impracticable to build the road, to ascertain if it were possible to dig a canal across the peninsula, from some point above the island to New Madrid. The idea of the canal was suggested to General Pope by General Schuyler Hamilton, an officer whose gentle refinement veiled his absolute resolution and endurance till they were called into practice by danger and privation.

Colonel Bissell found no place where a road could be constructed; but, by following up the bayou (called John's Bayou in the Confederate reports, called Wilson's Bayou on the map made by the United States engineers) which comes into the river immediately above New Madrid, he traced it into the swamp and found that, in connection with depressions and sloughs, a continuous, though tortuous water-way could be gained at that high stage of water, from a point in the river between Islands Eight and Nine and the river at New Madrid. The length of this channel was twelve miles. Part of it had to be excavated to get sufficient depth; for six miles it passed through a thick forest of large trees.

General Pope immediately sent to Cairo for four light-draught steamers, and tools, implements, and supplies needed to cut a navigable way. Colonel Bissell was at once ordered to set his entire command at work, and to call upon the land force on the fleet for aid if needed. For six miles Bissell had to cut through the forest a channel fifty feet wide and four and a half feet deep. Sawing through the trunks of large trees four and a half feet under the surface of the cold water was a work of extreme toil and great exposure. The trees when felled had to be disentangled, cut up, and thrust among the standing trees. Overhanging boughs of trees, growing outside the channel, had to be lopped off. Shallow places were excavated. The whole had to be done from the decks of the little working-boats, or by men standing in the water. The men were urged to incessant labor; yet they toiled with such ardor that urging was not needed. General Halleck telegraphed to Pope, Friday, March 21st, that he would not hamper him with any minute instructions, but would leave him to accomplish the object according to his own judgment, and added: "Buell will be with Grant and Smith by Monday." In nineteen days, April 4th, the way was open and clear; and on the 5th, steamers and barges were brought through near to the lower mouth, but not near enough to be in view from the river.

The Confederate officers on the island were aware of the attempt to secure this cut-off across the peninsula. Captain Gray, engineer, in a report or memorandum, dated March 29th, spoke of "the canal being cut by the enemy," and of heavy guns planted to be used against any boat that might issue from the bayou, as well as batteries erected along the shore, from about a mile and a half below New Madrid down to Tiptonville. But General McCown, when turning over the command to General W.W. Mackall, who relieved him on March 31st, said to him that the National troops were endeavoring to cut a canal across the peninsula, but they would fail, and that Mackall would find the position safe until the river fell, but no longer.

The task which General Pope had proposed to himself—to cross a wide, deep, rapid river, in the face of an enemy holding the farther shore in force, was sufficiently arduous at first. Now that Captain Gray's industry had lined the river-shore with batteries armed with twenty-four, thirty-two, and sixty-four pound guns, and eight-inch howitzers and columbiads, sufficient to blow out of the water any unarmed steamer that should venture to cross, the task was impracticable with his present resources. He applied to Commodore Foote, and urgently repeated the application, for two gunboats, or even one, to be sent down the river some dark night to engage these batteries below New Madrid. But the Commodore was not willing to risk his boats in a voyage along the front of miles of batteries, and declined. On March 28th Halleck telegraphed: "I have telegraphed to Commodore Foote to give you all the aid in his power. You have a difficult problem to solve. I will not embarrass you with instructions. I leave you to act as your judgment may deem best."

Pope set to work to make floating-batteries, to be manned by his troops. Each battery consisted of three heavy barges, lashed together and bolted with iron. The middle barge was bulkheaded all around, so as to have four feet of thickness of solid timber at both the ends and the sides. Three heavy guns were mounted on it and protected by traverses of sand-bags. It also carried eighty sharpshooters. The barges outside of it had a first layer, in the bottom, of empty water-tight barrels, securely lashed, then layers of dry cotton-wood rails and cotton-bales packed close. These were floored over at the top to keep everything in place, so that a shot penetrating the outer barges would have to pass through twenty feet of rails and cotton before reaching the middle one, which carried the men and guns. The outer barges, thus bulkheaded with water-tight barrels and buoyant cotton-bales, could not sink. These barges, when all was ready, were to be towed by steamers to a point directly opposite New Madrid. This could be done safely, as the shore at the point and for a mile and a half below was swamp, and the nearest battery was necessarily below the swamp. When near the opposite shore the floating-batteries were to be cut loose from the steamers and allowed to float down-stream to the point selected for the landing of the troops. As soon as they arrived within short range they were to drop anchor and open fire.

Meanwhile Commander Henry Walke had volunteered to take his boat, the Carondelet; and, on March 30th, Flag-officer Foote gave him permission to make the attempt on the first dark night. The morning of April 4th was a busy time on the Carondelet. The deck was covered with heavy planks, surplus chains were coiled over the most vulnerable parts of the boat, an eleven-inch hawser was wound around the pilot-house as high as the windows; barriers of cordwood were built about the boilers. After sunset, the atmosphere became hazy and the sky overcast. Guns were run back, ports closed, and the sailors armed to resist boarders. Directions were given to sink the boat if it became liable to fall into the enemy's hands. At dusk, twenty sharpshooters from the Forty-second Illinois came aboard to be ready to aid the crew in resisting boarders. After dark, a coal-barge laden with baled hay was fastened to the port side of the boat.

At ten o'clock the moon had gone down and a storm was gathering. The Carondelet cast loose and steamed slowly down the river. The machinery was adjusted so as to permit the steam to escape through the wheel-house, and avoid the noise of puffing through the pipes. The boat glided noiseless and invisible through the darkness. Scarcely had it advanced half a mile when the soot in the chimneys caught fire, a blaze shot up five feet above the smoke-stack. The flue-caps were opened, the blaze subsided, and all was yet silent along the shore. The soot in the smoke-stacks not being moistened by the steam, which was now escaping through the wheel-house, became very inflammable. Just as the Carondelet was passing by the upper battery—the redan—the treacherous flame again leaped from the chimneys, revealing and proclaiming the mission of the boat. Sentries on the parapets on shore fired, guards turned out, rockets darted skyward; the heavy guns opened fire; and the brooding storm broke forth, the lightning and thunder above drowning the flashes and war below. The lightning revealed the position of the gunboat, but it also disclosed the outline of the shore, enabling the pilots to steer with certainty. The boat was pushed near to the Tennessee shore and to the island, and put to its greatest speed. Impeded by the barge in tow, its greatest speed was slow progress, and for half an hour the gunners in the batteries watched the black night to see the hurrying Carondelet shot for an instant out of the darkness at every lightning flash. Beyond the batteries lay the floating battery, carrying nine guns, which had been driven from its moorings the day before by the heavy fire of the fleet. A light on the floating battery marked its position. A few shots left it, but it evinced no eagerness to join in conflict. The Carondelet, unharmed, untouched, fired the agreed signal, and fleet and army knew at midnight the passage was a success.