The New Student's Reference Work/Bore

Bore, also called Eagre, a peculiar tidal effect at the mouth of certain rivers. When a river's mouth widens rapidly, and it is subject to high tides, the spring flood-tide drives an immense volume of water from the sea into the river. The water collects in the mouth faster than it can flow up into the river, and so there is gradually formed a kind of watery ridge stretching across and rushing up the opening with great violence and noise. It sometimes rises many feet. The most notable Old World bores are those of the Ganges, Brahmaputra and Indus. In one branch of the Ganges the bore travels seventy miles in four hours, and often it appears suddenly as a wall seven feet high.