Thus, the tide takes no less than twelve hours for its progress from the mouth of the Thames to London, about the time it requires to travel all the way from Van Diemen's Land to the Cape of Good Hope. Consequently, when it is high-water at the mouth of the Thames at three o'clock in the afternoon, for instance, we have not high-water at London Bridge before three o'clock in the following morning, when it is again high water at the Nore. But, in the mean time, there has been low water at the Nore and high water about half-way to London, and while the high water is proceeding to London, it is ebbing at the intermediate places, and is low water there when it is high water at London and at the Nore. If the tide extended as far beyond London as London is from the Nore, we should have three high waters with two low waters interposed. The most remarkable instance of this kind is afforded by the gigantic river of the Amazons, as it appears by the observations of Condamine and others, that, between Para, at the mouth of the colossal stream, and the conflux of the Madera and Marañon, there are no less than seven simultaneous high waters with six low waters between them. Thus, four days after the tide-wave was first raised in the Southern Ocean, its last undulations expire deep in the bosom of the South American wilds. The Mediterranean is generally supposed to be tideless, but this opinion is erroneous; and in the Adriatic, the flux of the sea is far from being inconsiderable, for, at Venice, the difference between high and low water is sometimes no less than six or even nine feet. Mr. W. Trevelyan, during a summer residence in the old port of Antium, on the Roman coast, found from a series of accurate observations, that the tides regularly succeed each other and attain a height of fourteen inches. In the eastern Mediterranean new measurements have proved that they are still more considerable, while in the western part of that inclosed sea they are almost imperceptible. The differences of level caused by the Mediterranean tides, are indeed too inconsiderable to attract the general notice of the inhabitants on the coast, but in the famed Euripus, the narrow channel which separates the island of Eubœa or Negropont from continental Greece, the tide produces the striking phenomenon of very irregular fluctuations of the waters, from one end of the channel to the other.