Not long after the rebels had taken possession of the Navy Yard the Merrimac was raised, and placed in the floating-dock. Here she was remodeled, and covered by a sloping roof of iron plates, four inches thick, which bore her down so heavily, that it became almost impossible to launch her. When launched she drew four feet of water over the calculated draught, and was again placed upon the dry-dock, and underwent material changes in her construction. Her bow and stern were steel-clad, and the bow furnished with a projecting ram for the purpose of piercing an antagonist. The armament consisted of four eleven-inch navy guns, broadside, and two one hundred-pounder rifled guns, at the bow and at the stern. The Monitor was built by contract, under the act of Congress of July, 1861, appropriating $1,500,000 for iron-clad vessels. Captain Ericsson presented proposals for a battery to be launched within one hundred working days from the date of the contract. The contract was awarded to him in October, and on the one hundred and first working day the Monitor was launched from the Continental Iron Works at Greenpoint, New York. The Monitor is low, wide, and flat-bottomed, with vertical sides, and pointed ends, requiring but shallow water to float in. The sides of the vessel are formed of plate iron, half an inch thick, outside of which is attached solid white oak twenty-six inches thick: outside this again is rolled iron armor five inches thick. The inclination of the lower hull is such that a ball to strike it in any part must pass through at least twenty-five feet of water, and then strike an inclined iron surface at an angle of about ten degrees. In the event of an enemy boarding the battery they can do no harm, as the only entrance is at the top of the turret or citadel, which cannot easily be scaled, and even then only one man at a time can descend into the hull. [Illustration: BIRDS-EYE VIEW OF HAMPTON ROADS, VA., MARCH 8, 1862. 1. Hampton Roads.—2. Fortress Monroe.—3. Rip Raps.—4. Newport News Point.—5. James River.—6. Sewall’s Point.—7. Pigs Point.—8. Craney Island.—9. Elizabeth River.—10. Norfolk.—11. Portsmouth.—12. Gosport.—13. Suffolk.—14. Nansemond River.—15. Merrimac.—16. Monitor.—17. Cumberland.—18. Congress.—19. Minnesota.—20. Yorktown.—21. Jamestown.—22. St. Lawrence.—23. Roanoke. ]