Hickman, KY, March 15—The powerful naval expedition, composed of the gunboats Benton, Louisville, Cincinnati, Carondelet and Conestoga, under Commodore Foote, left Cairo at 7 o’clock this morning. At Columbus they were joined by the gunboats Pittsburg, St. Louis and Mound City, making a total of eight gunboats, and were overtaken by eight mortar boats In tow of four steamers, with transports and ordnance boats. The fleet arrived here at 4 1/2 o’clock this afternoon. Mounted pickets of the enemy were in sight on the bluff on our arrival, and two companies of the 27th Illinois were sent after them, but they escaped.