A ship in the darkness of a foggy night thought another ship was approaching and signaled for it to change course 10 degrees to the south. The reply came asking instead that the ship sending the message change course 10 degrees to the north. Irritated, the captain of the ship repeated, "Change course 10 degrees to the south". For effect he added, "I am a captain!" This time the answer came back, "Change your course 10 degrees to the north, I am a boatswain." "Change your course 10 degrees to the south", the captain ordered and added "I am a battleship." The exchange ended when the boatswain confidently stated, "Change your course 10 degrees to the north, I am a lighthouse"!