steamers came down and attacked the _Congress_ with such effect that her commander tried to run her ashore. Having finished the _Cumberland_, the _Merrimac_ came up and opened a deliberate attack on the _Congress_, and finally set her on fire, when the crew escaped in their boats. She burned for several hours, and in the night blew up. Of the other National vessels in the Roads, one got aground in water too shallow for the _Merrimac_ to approach her, and the others were not drawn into the fight. The next morning the _Merrimac_ came down again from Norfolk to finish up the fleet in Hampton Roads, and after that--to do various unheard-of things. The more sanguine expected her to go at once to Philadelphia, New York, and other seaboard cities of the North, and either bombard them or lay them under heavy contribution. The National Administration entertained a corresponding apprehension, and expected to see the _Merrimac_ ascend the Potomac and attack Washington first. A part of these expectations were well founded, and the rest were such exaggerations as commonly arise from ignorance. The _Merrimac_ could not have reached New York or Philadelphia, because she was not a sea-going vessel. With skilful management and good luck, she might have ascended the Potomac to Washington, but she would have had to run the gantlet of numerous dangers. There is a place in the Potomac called "the kettle-bottoms," where a great many conical mounds, composed of sand and oyster-shells, rise from the channel till their peaks are within a few feet of the surface; and their positions were so imperfectly known at this time that the National vessels frequently ran aground upon them. Several devices were in waiting to make trouble for the iron-clad champion at this point, perhaps the most dangerous of which was that prepared by Captain Love, commanding an armed tugboat. He procured a seine three-quarters of a mile long, took off its floats, and stretched it across the channel in such a way that the _Merrimac_ could hardly have passed over it without fouling her propeller, which would have rendered her helpless. [Illustration: JOHN ERICSSON. Inventor of the "Monitor."] [Illustration: LIEUTENANT G. U. MORRIS. Commander of the "Cumberland."] [Illustration: REAR-ADMIRAL J. SMITH. Commander at the Washington Navy Yard.]