5. After the Confederates evacuated Columbus, Kentucky, they fortified Island Number Ten in the Mississippi, opposite New Madrid. Against this place General Pope advanced with a body of Western troops, while Commodore Foote descended the Mississippi with his gunboats. Pope captured New Madrid; and for twenty-three days Island Number Ten was besieged. On the 7th of April the Confederates attempted to escape; but Pope had cut off the retreat, and the garrison, numbering five thousand, was captured. On the 6th of June the city of Memphis was taken by the fleet of Commodore Davis. 6. Early in the year General Curtis pushed forward into Arkansas, and took position at Pea Ridge, among the mountains. Here he was attacked on the 6th of March by a Confederate force of twenty thousand men, which included a large number of Indians from the adjacent Indian Territory. A hard-fought battle ensued, lasting for two days, in which the Federals were victorious. [Sidenote: The Merrimac and the Monitor.] 7. After the destruction of the navy yard at Norfolk, the Confederates had raised the frigate _Merrimac_, one of the sunken ships, and plated the sides with iron. The vessel was then sent to attack the Union fleet at Fortress Monroe. Reaching that place on the 8th of March, the _Merrimac_ began the work of destruction; and two valuable vessels, the _Cumberland_ and the _Congress_, were sent to the bottom. During the night, however, a strange ship, called the _Monitor_, invented by Captain John Ericsson, arrived from New York; and on the following morning the two iron-clad monsters turned their enginery upon each other. After fighting for five hours, the _Merrimac_ was obliged to retire to Norfolk, badly damaged. [Illustration: Merrimac and Monitor.] 8. On the 8th of February a Federal squadron attacked the Confederate fortifications on Roanoke Island. The garrison, nearly three thousand strong, were taken prisoners. Burnside next proceeded against Newbern, and on the 14th of March captured the city. Proceeding southward, he reached the harbor of Beaufort, and on the 25th of April took possession of the town. [Sidenote: Capture of New Orleans.] 9. On the 11th of the same month Fort Pulaski, at the mouth of the Savannah, surrendered to General Gillmore. Early in April, a powerful squadron, under General Butler and Admiral Farragut, ascended the Mississippi and attacked Forts Jackson and St. Philip, thirty miles above the Gulf. From the 18th to the 24th the fight continued without cessation. At the end of that time Admiral Farragut succeeded in running past the batteries. On the next day he reached New Orleans, and captured the city. General Butler became commandant, and the fortifications were manned with fifteen thousand Federal soldiers. Three days afterwards, Forts Jackson and St. Philip surrendered to Admiral Porter. [Sidenote: Campaign in Kentucky.]