Movements on the Potomac.
--The Alexandria Gazette, of yesterday, says:‘ The United States steamer Columbia, as she passed by this city on Saturday last, saluted, by lowering and hoisting her flag three times, the British brigantine ‘"Onward,"’ which was lying at the Prince street wharf gaily dressed in bunting.
The United States steamer Empire City, as she steamed by the Pawnee, now lying off this city, on Sunday morning, had her rigging manned, and cheered the United States flag flying at the Pawnee's peak. The salute was returned by the crew of the Pawnee.
The schooner Cornelia, from Philadelphia, with provisions for the District of Columbia, went up yesterday morning.
The United States steam frigate Pocahontas, with an oyster schooner in tow, passed by yesterday at noon.
The United States steamer Mount Vernon, with a load of buoys to replace those which have been removed from the Potomac, went down the river yesterday evening. When opposite this city, she sent an officer and four soldiers aboard the Pawnee.
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