Al Som (Nan Do) (40°39'N., 129°33'E.), about 11.3 miles E of Yujin Dan, is a conspicuous white, barren, rocky islet. The two rocks close E of the islet are very pointed. Al Som, a good mark for vessels running the coast, is reported to be altered in appearance due to a mirage occurring from about the middle of May to the end of July.

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