To celebrate the 30th Navigation Day, this Directorate released a commemorative issue which depicts a large, modern container ship and an oil tanker respectively. The navigation industry in our country dates from the dynasties of Chin (221-206 B.C.) and Han (206 B.C.-220 A.D.).By the early 15th century, Cheng Ho had made seven oceanic expeditions to the South Pacific and along the Indian Ocean coasts.This record in the history books attests to our early achievements in navigation.In recent years, because of rapid progress in economic growth and international trade, the navigation industry has become even more indispensable.