The demonstration had one good effect; that of ascertaining the fact that the number of guns, at the principal work on Sewell’s Point, was greatly reduced, and the force of men posted there comparatively small. On the 10th of May the rebels learned that a large force of Union men were marching rapidly upon Norfolk, and later in the day that the Union troops occupied the city. They at once endeavored to put in force a design to get up the river, and aid in the defence of Richmond, trusting to be able to do this before the Union officers should learn of their intention. Before daybreak the next morning, however, it was found that the Merrimac was not fit for action; and the rebel flag-officer in command determined, with the concurrence of the first and flag-lieutenants, to land the crew at Craney Island, the only means of retreat left open to them; and, as it was otherwise impossible to prevent the Merrimac from falling into our hands, to destroy her before we could capture her. The vessel was accordingly put ashore, near the main land, the crew was landed, and in a few minutes sheets of flame rose into the air fore and aft of the proud rebel iron-clad. For more than an hour she burned fiercely; tongues of fire licked her sides and shot up livid streams of light through the dense smoke, and at 5 o’clock on the morning of May 11th, with a loud report, like a roar of baffled rage, agony, and mortification, she blew up, scattering her ruins far and wide; and the morning sun shone down on nothing of the Merrimac save wreck and smoke. THE BATTLE OF HANOVER COURT-HOUSE. MAY 23, 1862. On Wednesday, May 28th, one of the most brilliant achievements was consummated which distinguished the great, patriotic war for the Union. For several days previously to the above date, the rebels, returning from their raid up the Shenandoah valley, had been extending their pickets towards Old Church, throwing forces upon McClellan’s right flank, and otherwise indicating that they meant mischief. These threats of battle were answered by his suddenly throwing out a heavy Union force, between Hanover and Richmond, which cut off their communications by the Virginia Central, and the Richmond and Petersburg railroads. By this means the Union army totally dispersed the enemy, in two short, sharp engagements, cleared its flank, and disabled the rebel railroad operations. But a more important work was ahead; and the force selected for it was General G. W. Morrell’s division, of General F. J. Porter’s Fifth Provisional Army Corps. At midnight of Monday, orders were given to each regiment to be in light marching trim, for the morning. The reveille beat at 3 A. M. A drenching rain was pouring down, so that not so much as a cup of coffee could be heated; and there was nothing but cold rations to give the required strength for the prospective march.