There she sat upon the water a glorious impregnable battery, the wonder of the age, the terror of rebels, and the pride of the North. The Monitor is so novel in structure that a minute description will be necessary to convey an accurate idea of her character. "She has two hulls. The lower one is of iron, five-eighths of an inch thick. The bottom is flat, and six feet six inches in depth--sharp at both ends, the cut-water retreating at an angle of about thirty degrees. The sides, instead of having the ordinary bulge, incline at an angle of about fifty-one degrees. This hull is one hundred and twenty-four feet long, and thirty-four feet broad at the top. Resting on this is the upper hull, flat-bottomed, and both longer and wider than the lower hull, so that it projects over in every direction, like the guards of a steamboat. It is one hundred and seventy-four feet long, forty-one feet four inches wide, and five feet deep. These sides constitute the armor of the vessel. In the first place is an inner guard of iron, half an inch thick. To this is fastened a wall of white oak, placed endways, and thirty inches thick, to which are bolted six plates of iron, each an inch thick, thus making a solid wall of thirty-six and a half inches of wood and iron. This hull is fastened upon the lower hull, so that the latter is entirely submerged, and the upper one sinks down three feet into the water. Thus but two feet of hull are exposed to a shot. The under hull is so guarded by the projecting upper hull, that a ball, to strike it, would have to pass through twenty-five feet of water. The upper hull is also pointed at both ends. The deck comes flush with the top of the hull, and is made bomb-proof. No railing or bulwark rises above the deck. The projecting ends serve as a protection to the propeller, rudder and anchor, which cannot be struck. Neither the anchor or chain is ever exposed. The anchor is peculiar, being very short, but heavy. It is hoisted into a place fitted for it, outside of the lower hull, but within the impenetrable shield of the upper one. On the deck are but two structures rising above the surface, the pilot-house and turret. The pilot-house is forward, made of plates of iron, the whole about ten inches in thickness, and shot-proof. Small slits and holes are cut through, to enable the pilot to see his course. The turret, which is apparently the main feature of the battery, is a round cylinder, twenty feet in interior diameter, and nine feet high. It is built entirely of iron plates, one inch in thickness, eight of them securely bolted together, one over another. Within this is a lining of one-inch iron, acting as a damper to deaden the effects of a concussion when struck by a ball--thus there is a shield of nine inches of iron. The turret rests on a bed-plate, or ring, of composition, which is fastened to the deck. To help support the weight, which is about a hundred tons, a vertical shaft, ten