On Sunday morning, March 9, the _Merrimac_ renewed her attack upon the _Minnesota_, and was completely surprised by the appearance of a small vessel which, in the expressive description of the day, resembled a cheese- box on a raft.

She had arrived from New York at the close of the first day's fight.

From her turret began a furious cannonade which not only diverted the attack from the _Minnesota_ but after a ferocious contest of many hours practically destroyed the _Merrimac_, which was compelled to seek the shelter of Confederate batteries at Sewell's Point, and never re-appeared in service.

The relief to the North by this victory was incalculable.

Not only had the _Merrimac_ been stopped in her expected bombardment of Northern cities, but the success of the _Monitor_ assured to the government a class of armor-plated vessels that could be of great value in the coast service to which our naval operations were principally confined.