There are seamless mountains on both sides of the Three Gorges stretching more than 200 miles. The overlapping rocks make up layers of barriers that shield against sky and sunshine so that the sun can only be seen at noon and the moon will merely show at midnight. In summers, water rises to lofty mountains, making all boats floating along or against the river get blocked. Suppose an empire has an urgent decree to issue from Baidi, it will reach Jiangling at sunset of the day. The distance between them is about 373 miles, and neither a galloping horse nor a flight can run faster than a boat.