FACTS ABOUT THE TIDE.

New Zealand Mail, Issue 1715, 11 January 1905, Page 73 (Supplement)

FACTS ABOUT THE TIDE.

To the ordinary landsman the tidea along the coast are most piizzling. He has been taught that the tides rise and. fall twice in the twenty-four hours, and that thi* depends in some mysterious way upon tne moon. But when it occurs that in his travels he sees a spot along the shore -where there is no tide at all he is at a loss to explain this phenomenon. To be quite exact, there is only one ocean in the world where the tides follow the moon with absolute regularity. This is the great Antarctic basin, and the reason is that there, and there only, is to be found a sweep of ivater winch is entirely uninterrupted by land. The enormous wave raised by the moon’s attraction courses round the world south of Cape Horn and the Cape of Good Hope with absolutely nothing to break it. In the northern hemisphere great masses of land interrupt the tidal waves and, combined with the shallowness of the inland seas, cause them to perform antics which seem most strange.

The depth of the water has much to do with tidal irregularities/ Out in the open .ocean, where the tide is abysmal—that is, about five thousand fathoms—the speed of the waves is amazing. Where the depth decreases to five fathoms the tide cannot travel more than fifteen miles an hour. In England, for example, which is surrounded by narrow, landbroken seas, the result is that they get some of the most terrible and dangerous tidal races and currents to be found anywhere m the world. The most tor** midable of these is the whirlpool between, the islands of Jura and Scarba, on thei west coast of Scotland. This is known, as “the Cauldron of the Spotted Seas.’ Here is a race running at a speed to be matched only by a mountain torrent. The force of a heavy tidal current pushing up a wide-mouthed river causes what is teroted a ‘‘bore.” The most striking example of this tidal feature is seen on the Amazon, a moving wall of ivater thirty ieet in height, and reaching from bank to bank, rushing inland from the ocean.