The most important operations of the navy during the year were those on the Mississippi river, and before Charleston, which have been already described in connection with army movements. The work of building vessels for naval purposes was carried on vigorously during the year, and, inclusive of vessels purchased, and those captured from the enemy, fifty-eight vessels, mounting four hundred and fifty-two guns, with a tonnage of fifty thousand tons, were added; while the loss for the same period was thirty-four vessels of about sixteen thousand tons, including the iron-clads Monitor and Weehawken, which foundered in stormy weather. The number of seamen on the register was about thirty-four thousand. At daylight on January 29, an iron propeller named Princess Royal attempted to enter Charleston harbor, but was captured by the gunboat Unadilla. This was one of the most valuable prizes taken during the war. The cargo would have been of great service to the enemy, who immediately set on foot a daring scheme to recover her. Accordingly, before daylight on the 31st, two rebel rams, the Palmetto State and the Chicora, under Commodore Ingraham, came down the channel, and surprised the smaller vessels of the blockading squadron, which lay close in shore. The Mercedita was the first vessel attacked, which was rendered helpless by the explosion of a 7-inch shell from the Palmetto State in her port boiler, and surrendered. The Keystone State was then attacked by both rams, and made a most gallant defence, but being disabled, she was compelled to pull down her flag, but re-hoisted it when she found the enemy did not discontinue his fire. Other vessels making their appearance, the rams soon after discontinued the attack, and both the disabled Federal vessels were taken in tow by their consorts. It was claimed by General Beauregard and Flag-officer Ingraham that the blockade had been raised in accordance with the laws of war, as there were no Federal vessels in sight from Charleston at daylight on the 1st of February; and the foreign consular agents in Charleston were induced to indorse this claim, but the assumption remained unnoticed by foreign governments. On January 30, the Federal gunboat Isaac Smith, Lieutenant Conover, was captured on Stono river, S. C., by masked shore batteries, after losing twenty-four men in killed and wounded. On the 27th of February, the Montauk monitor destroyed the rebel steamer Nashville, under the guns of Fort McAllister.