<P> The first tide table in China was recorded in 1056 AD primarily for visitors wishing to see the famous tidal bore in the Qiantang River . The first known British tide table is thought to be that of John Wallingford, who died Abbot of St. Albans in 1213, based on high water occurring 48 minutes later each day, and three hours earlier at the Thames mouth than upriver at London . </P> <P> William Thomson (Lord Kelvin) led the first systematic harmonic analysis of tidal records starting in 1867 . The main result was the building of a tide - predicting machine using a system of pulleys to add together six harmonic time functions . It was "programmed" by resetting gears and chains to adjust phasing and amplitudes . Similar machines were used until the 1960s . </P> <P> The first known sea - level record of an entire spring--neap cycle was made in 1831 on the Navy Dock in the Thames Estuary . Many large ports had automatic tide gauge stations by 1850 . </P> <P> William Whewell first mapped co-tidal lines ending with a nearly global chart in 1836 . In order to make these maps consistent, he hypothesized the existence of amphidromes where co-tidal lines meet in the mid-ocean . These points of no tide were confirmed by measurement in 1840 by Captain Hewett, RN, from careful soundings in the North Sea . </P>

When does high tide and low tide occur