From 1894 to 1907 R. A. Harris, of the U. S. Coast Survey, published his Manual of Tides. This work contained charts showing cotidal lines for the whole world, based on theories and hypotheses the leading feature of which was the principle of resonance. It was assumed that in each ocean there exist regions capable of free oscillation with a period near one of the principal tidal periods, and that the nature of these free oscillations may be calculated approximately, without allowing for the earth's rotation or the interaction with neighbouring regions.
Since 190o a number of Scandinavian oceanographers, notably V. W. Ekman, 0. Pettersson and J. P. Jacobsen, have invented current-meters and L. Faye has observed tidal elevations in the open sea by means of his self-registering instrument.
In 1912 A. Blondel applied the "narrow sea theory," through the principle of least action, to the tides of the Red Sea (Ann. Fee. Toulouse). From 1913 to 192o R. Sterneck and A. Defant developed the narrow sea theory with special reference to the Adriatic Sea (Akad. Wiss. Wien; Ann. der Ilydrog.). Defant applied this theory to the Red Sea, the Persian Gulf, the English Channel and the Irish Sea, and parts of fig. 2 are based on his work.
Since about 1895 the dynamical theory of tides and seiches has been much advanced by the mathematicians: H. Lamb, H. H. Hough, H. Poincare, Lord Rayleigh, G. Chrystal, E. Fichot, G. R. Goldsbrough, G. I Taylor, H. Jeffreys, G. Bertrand, S. Goldstein and J. Proudman; while since 1920 much has been done on the analysis of observations by A. T. Doodson, K. Hessen and H. Rauschelbach.
BIBLioGRAPHY.---History: Harris's Manual (1897). General: G. H. Darwin, The Tides and Kindred Phenomena in the Solar System (3rd ed. 1911) ; • E. Fichot, Les marees et leer utilisation industrielle (5923) : H. A. Marmer, The Tide (1926) ; A. Defant, Gezeitenprob leme des Meeres in Landrahe (1925) . See also Kelvin's collected Mathematical and Physical Papers, G. H. Darwin's collected Scientific Papers and the various treatises and papers referred to in the article. For information on actual tides see the Admiralty Tide Tables, Part II., and tables published by the U.S. Coast and Geodetic Survey. For full bibliographies see J. C. Houzeau and A. Lancaster, Biblio graphie de l'astronomie (1882), and a bibliography of publicaticons from 1910-1927 published by the International Union for Geodesy and Geophysics. (J. PR.)