 Complete the following phrase:  Assigned to Comdr. David Porters Mortar Flotilla, the schooner sailed for Key West, Florida, where the other ships of the force assembled before moving on to Ship Island, Mississippi, on 6 March. On the 18th, the mortar boats were towed across the bar at Pass a LOutre into the Mississippi River. A month later, the flotilla moved upstream to positions below 