Curious Facts About the Tide

New Zealand Tablet, 25 October 1906, Page 13

Curious Facts About the Tide

To the ordinaiy landsman the tides along the coast are most puzzling. He has been taught that the tides rise and fall twice in twenty -four hours, and that this depends in some mysterious way upon the 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-H/his\r'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 water which 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. Here in our northern hemisphere great masses of land interrupt the 1 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 iio 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, land broken seas, the result is that --they get some of ;the most terrible and . dangerous tidal races and currents to "be ' found - anywhere in the world. The most formidable" of these'is the whirlpool between the islands of. Jura and Scarba, on the west coast of Scotland. This is' known as 'the Caldron of the Spotted Seas.'- Here is a race running .at a speed to b.e matched only by a mountain ' torrent. The force of a heavy tidal current pushing up a wide mouthed river causes what is termed a ' bore. ' The most - striking example of this tidal feature is seen on the" Amazon, a moving wall of water thirty feet in height, and reaching from bank to bank, rushing inland from the ocean.