TIDAL MYSTERIES.

Dominion, Volume 1, Issue 239, 2 July 1908, Page 10

TIDAL MYSTERIES.

DISCUSSION BY PHILOSOPHICAL SOCIETY. IMPROVED LOCAL GAUGE. At the meeting of tlio Philosophical Society last evening Mr. C. E. Adams gave an interesting explanation of a uniquo tido gauge used" by tlio Wellington Harbour Board, and stationed at their N shed. A tido gauge is an object which marks on paper a chart of tlio riso and fall of tho tide. This particular instrument has an advantage over all other gauges known to Mr. Adams, in that no clock mcchanism is involved. Ho velieved that tho principle of the gaugo was entirely due to Mr. W. Ferguson. It seemed to him that a description of the instrument should be. published by,: tho Society, so that they might learn if any ono elso laid claim to the improvement. Mr. Adams also gavo somo interesting information on tho subject of tide records, and tho method of prediction of tides. Ho stated that co-tidal lines which had been worked out causod scientists to postulate the existenco of spaces in the ocean where there wore no tides. One such plaeo- was theorised to exist westward from New Zealand. As tho depth was very great at several of these spots, the theory had not been tested, but at ono place off the coast of Holland soundings had been taken in shallow water, and no tidal movement was discovered. Mr. Adams stated. that Mr. '1. Wright, of Eastbourne; England, had worked out tidal figures relating to Wellington, and would probably report on them to the. Royal Society. He had also dealt with tidal figures for Auckland, and v. - as now similarly engaged, tho speaker thought, in regard to those of Lyttoiton and Dunedin. Theso New Zealand figures were expected to reveal somo interesting features. Thero are a number of tide gauges round the Now Zealand coast, and Mr. Adams suggested that; it would add to present knowledge if automatic gauges could be stationed some of the outlying islands. Ho thought that gauges like that used by tho Wellington Harbour Board could be arranged, so that they would run for a long Jame —long enough for. observations to ■ be taken on visits to tlio islands. Ho thought that this was a matter which tho Society might well tako

up. . ■' , , ■Mr. Y\'. Ferguson said that lie had never thought of taking any credit for the improvement in the gauge until Mr. Adams made the suggestion. Twenty-ono or twenty-two. years ago, when the gauge was constructed, the Harbour Board had to practice strict economy, and it was difficult to obtain autho-. rity for even small expensos. He then asked the Board for two gauges, one to be placed at' Worser Bay and one at the: wharf, but the Board did not grant both. Ho was sorry that tho second gauge was not erected, though of recent years the Government had established a gaugo at Shelly Bay. He devised • tho gaugo in its present form solely ou account of cheapness. Mr. Ferguson referred to peculiar secondary undulations shown on the Wellington tidal records, and stated that it would bo very interesting to learn to what oxtent thoy existed lit tho'mouth of the harbour, and also in tno open sea. Ifc was only recently 'that a method, had been discovered of taking tidal records in the open sea, and he did not know if it had proved successful. If it had, important information would probably bo obtained with regard to wave lovels, as well as tidal motions. ' Tho wildest statements had been mado by engineers regarding hoight3 of ivavos and their consequent pressure. One advantage of the Harbour Board's guago was that it enabled drawings to bo mado on a larger- scale than was ordinarily tho case. Mr. A. Hamilton thought that there would bo on difficulty in establishing gauges on tho Campbell and Chatham Islands, where there wore permanent residents. 110 thought that tho Society should make representations in regard to this matter. Mr. Ferguson said ho thought that tho reason why tho secondary uudulations wcro shown by the Wellington fcauge, and not by. the other New Zealand, gauges'was that the cealo of the other records was not largo enough "for their delineaton. If gauges were placed oil the outlying islands, charts should no sufficiently largo to mark tlieso secondary motions. Tho undulations, Mr. Ferguson stated, were found in all large mosses of water, even where there was hardly any tide. They had not yet been explained 'by scientists.

i Mr. Hamilton said that' thoy '.had-been noticed in Lakes To Allan and Wakatipu. In . the latter lake,. csjiccally, somo very peculiar motions of this kind had'been observed. .

An interesting discussion followed, in the course of whch air. Martin Chapman, K.G., expressed the opinion that a set of gauges should bo stationed at Lako AVnkatipu for about a year, and nfforwards removed to other lakes.