NEW TIDE-GAUGES.

Dominion, Volume 2, Issue 475, 6 April 1909, Page 8

NEW TIDE-GAUGES.

Important work has just been done by Mr. Thos. Humphries, who has now retired from the position of Surveyor-General. This has been the task of accurately determining the mean tides at different points of the- coast of New Zealand, with chief stations at Auckland, Wellington, Lvttolton, and Dunedin. The- method followed is interesting. With tho aid of a tide-gauge a zero point is fixed at certain places "on tho solid." Copper bolts are driven into structures as nearly permanent as it is possible to find them, and, by observation extending over months, tho moan tide at the points of observation is worked out, and noted down. Such figures aro placed on permanent record, so that, at any timo in the future, it will bo aseertainahlo exactly what tho mean tido was at each place. "Of" course," said Mr. Humphries, "an ordinary record could lw easily lost or destroyed, but I am dealing with tho matter pretty, fully in my annual report, so that it will bo always on record what the mean tido is to-day, for example. This is a very im-port-ant thing. They study it in India, wlicro it is made a subject in tho marine examinations, and tho result of such observations, extending over a number of years, is taken into consideration when docks and other big watcrsido works are being constructed." "I am sure," continued Mr. Humphries, "that -Taranaki has risen some foot sinoo I was a boy, but thero is nothing on record to show that it is so. Where tho waves used to break at (ho back of tho old schoolgrouml a littlo up the Hoatoki stream is no\t high and dry—proof, to my mind, that the land in that vicinity must liavo risen, as it did. ( dowti hero after tho big carthauakes."