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TIDE 391 TIEDEMAN directly as their masses, and inversely as the cubes of their distances; hence the ratio of the disturbing force exerted by the sun to that exerted by the moon 7 : 16, The principal tidal wave is that caused by the moon, but on it must be superposed that due to the sun. When the sun and moon are in syzygy, at times of new and full moon, their tidal waves will be superposed crest on crest, and the effect will be what is called a spring tide. When they are in quadrature, trough will coincide with crest, the lunar tide will be partially neutralized by the solar tide, and the result vdll be the so-called neap tide. The average spring tide will be to the average neap tide as 16 + 7 : 16 — 7 = 23 : 9. Besides this effect in amplitude, an- other effect is caused by this combination of tides, namely the priming and lagging of the tides. For when the two vertices do not coincide, the maximum of the re- sultant tidal wave will be at a point intermediate to the vertices, so that the time of high water will be now in ad- vance now behind the time it would have been had the moon been the sole agent. Not only, then, are the waters of the ocean subject to diurnal and semi-diurnal oscillations, but these are subject to a monthly, semi-monthly, and even annual variation, besides being more or less af- fected by prevailing winds and coast configuration. The height of the tidal wave which circulates round the earth is not great — at most some 7 feet, a very small quantity compared to the size of our globe. In estuaries, bays, creeks, straits, etc,, however, the difference be- tween high and low water is much greater than this — as much as 50 feet in the Bay of Fundy, Nova Scotia. The explanation of such phenomena is to be found in the momentum with which the water is pushed forward by the ad- vancing wave. In such a sea as the Mediterranean, which is all but cut off from communication with the great oceans, and which is itself not sufficiently extensive to be very perceptibly acted on by the sun and moon, the tides are very small, not exceeding a few inches. The attempt to establish a complete theory from abstract principles has proved a failure ; and the only true meth- od by which to get an insight into the particular laws which govern tidal action at any given place is continued observa- tion. By means of Lord Kelvin's tide gauge a graphical representation of the tidal oscillation at any place can be easily obtained ; and by harmonic analysis of the curve, the constituent factors may be easily discovered, and the comparative effects of their several causes estimated. One efficient cause in retarding tides han not been mentioned, namely, fluid fric- tion, which, as first noticed by Kant, must act as a continual brake to the earth in its rotation; and this gradual slackening in the earth's speed of rota- tion must go on till the day is of the same length as the lunar month, when matters will be as required in the equilibrium theory given above. TIDE GAUGE, an instrument in har- bors to measure the rise and fall of the tides. A common form consists of a graduated spar, 24 feet long, and having boxes at the side, in which is a float with an elevated stem. The spar is secured to a pier or quay, or is anchored iu a frame and secured by guys. The rod is % inch in diameter, and is supported by a cork of three inches cube. The stem is guided by staples in the spar. TIECK, LUDWIG (tek), a German writer; bom in Berlin, Prussia, May 31, 1773. He was educated at the University of Halle, and at Gottingen and Erlangen. He published the tale of "Abdallah," and a novel entitled "William Lovell" (three vols. Berlin, 1795-1796). His "Peter Lebrecht, a History Without Adven- tures," and "Peter Lebrecht's Popular Tales." At Jena in 1799-1800, associat- ing with the two Schlegels, Brentano, etc., gave rise to the Romantic School of Ger- many, so called. In 1799 he published "Romantic Poems" (2 vols. 1799-1800), and in 1804 appeared his comedy "The Emperor Octavian." His "Phantasus" (3 vols. Berlin, 1812-1815), however, gave the first sign of his having freed himself from the mysticism and extrava- gances of his earlier works. In 1817 he visited England, where he collected mate- rial for his Shakespeare. He resided at Ziebingen till 1818, when he removed to Dresden. From this period date his fa- mous tales ultimately published complete in 12 volumes (Berhn, 1853), the princi- pal being "Dichterleben" (A Poet's Life — Shakespeare); "Der Tod des Poeten" (The Poet's Death — Camoens); the "Witches' Sabbath," etc. In 1826 he published his "Dramaturgic Leaves." His study of Shakespeare resulted in "Shakespeare's Vorschule" (2 vols. Leip- sic, 1823-1829); and the continuation of the German translation of Shakespeare commenced by Schlegel. Tieck was in- vited to the Prussian court in 1841, awarded a pension, the rank of a privy councillor and supervised the Prussian stage. He died in Berlin, April 28, 1853. His brother, Christian Friedrich (1776- 1851), was celebrated as a sculptor. TIEDEMAN, CHRISTOPHER GUS- TAVUS, an American Avriter on law;