DIKE or DYKE, a trench dug out of the earth for defen sive and other purposes (cf. Dutch dijk, Ger. Teich). Water naturally collects in such trenches, and hence the word is applied to natural and artificial channels filled with water, as appears in the names of many narrow waterways in East Anglia. "Dike" is also used of the bank of earth thrown up out of the ditch, and so of any embankment, dam or causeway, particularly the defensive works in Holland, the Fen district of England, and other low-lying districts which are liable to flooding by the sea or rivers. (See HOLLAND and FENS.) In Scotland any wall, fence or even hedge, used as a boundary, is called a dyke. In geology the term is applied to wall-like masses of rock (sometimes pro jecting beyond the surrounding surface) which fill up vertical or highly inclined fissures in the strata.