Transcriber's notes: (1) Numbers following letters (without space) like C2 were originally printed in subscript. Letter subscripts are preceded by an underscore, like C_n. (2) Characters following a carat (^) were printed in superscript. (3) Side-notes were relocated to function as titles of their respective paragraphs. (4) Macrons and breves above letters and dots below letters were not inserted. (5) [root] stands for the root symbol; [alpha], [beta], etc. for greek letters. (6) The following typographical errors have been corrected: ARTICLE HYDROMECHANICS: "... and [omega] the angular velocity about it generated by an impulse couple M, and M' is the couple required to set the surrounding medium in motion ..." 'impulse' amended from 'impluse'. ARTICLE HYMENOPTERA: "... see P. Cameron's British Phytophagous Hymenoptera (4 vols., London, Roy. Soc., 1882-1893)." 'Roy' amended from 'Ray'. ARTICLE HYRCANUS: "During its later years his reign was much disturbed, however, by the contentions for ascendancy which arose between the Pharisees and Sadducees, the two rival sects or parties which then for the first time (under those names at least) came into prominence." 'disturbed' amended from 'distrubed'. ARTICLE ICELAND: "Iceland is emphatically a land of proverbs, while of folk-tales, those other keys to the people's heart, there is plentiful store." 'people's' amended from 'poeple's'. ENCYCLOPAEDIA BRITANNICA A DICTIONARY OF ARTS, SCIENCES, LITERATURE AND GENERAL INFORMATION ELEVENTH EDITION VOLUME XIV, SLICE II Hydromechanics to Ichnography ARTICLES IN THIS SLICE: