A WORLD MYSTERY.

Otago Daily Times, Issue 19616, 21 October 1925, Page 8

A WORLD MYSTERY.

WHERE THE TIDE COMES FROM. Much mystery still envelopes the actual process of the birth of the tides. This much "wo do know; every 12 hours and a few minutes, out of the vasty wastes of midAtlantic, a gigantic "tide wave" is born. Strange as jthe fact sounds, this wave travels at the rate of hundreds of miles an hour, writes "'A. Traveller" in the Daily Chronicle. Its \ery sweed, however, makes jt of imperceptible height, for it is more than 1000 miles wide, from front to back. It hits what geographers call "the Continental shelf (the outlying shallows of Europe, on which the British Isles are perched) from the direction of about W.S.W. The shallow waters abruptly slow it up to a mere 90 miles an hour, simultaneously steepening the wave. The racing Atlantic tide wave first hits the west coast of Ireland, on which it splits, then sweeping around the mainland of Britain by the channel between the Orkneys and Scotland to the north and by the English Channel to the south. It reaches Liverpool (behind Ireland), the northernmost tip of Scotland and Dover a<bout simultaneously. Once round Thurso, the onracing tide, steadily losing momentum, reaches the Thames estuary some 12 hours later. Its journey down "the North Sea is a leisurely 50-mile-an-hour trip. There is a most curious "dead-water area" out in the North Sea, half-way between Holland and England, where the tide thrust a from north and south happen to neutralise each other, and no tide occurs in consequence. The biggest range of tides in Europe—and even. I believe, in the world—are those in the Channel Isles and along the Breton coast between Granville ard Brest, where the big main thrusts of the Atlantic tidal wave pile into the comparatively narrow neck of the channel.