e.—ia

Standard Surveys. Good progress in this work has been made in the Auckland and Invercargill metropolitan areas, and a small extension to the Christchurch standard survey was commenced. Rural standard, work has been in progress in other land districts. The reconstruction of main highways has necessitated considerable work in protecting and replacing standard survey-marks. Field Inspections. Field inspections have been carried out in most districts, and the results, with one or two exceptions, show that the high standard of survey-work in the Dominion has been maintained. Tidal Survey. The tide-tables for the year 1931, for the seven New Zealand standard ports (Auckland, New Plymouth, Wellington, Lyttelton, Dunedin, Bluff, and Westport) for which tidal predictions are published, were received in Wellington on the 2nd July, 1929, from the Hydrographer to the Admiralty. The work of measuring the times and heights of high and low water was again performed at the Tidal Institute, University of Liverpool, England. Investigations in connection with any movement in the Earth's crust at Westport in. relation to mean sea-level, resulting from the disastrous earthquake which occurred in June, 1929, are in hand, the period covered extending from June, 1928, to June, 1930. The results of this investigation will be published in the annual report for 1931. Magnetic Observatory. During the year the work of the Magnetic Observatory has been successfully carried on. The hourly values of the magnetic declination, horizontal magnetic force, and vertical magnetic force have been computed from the measurements of the hourly values obtained daily by means of the Eschenhagen magnetographs installed at Amberley Substation. The resulting mean values for the year 1929 reduced to Christchurch Absolute House values, are as follows : — Mean Value, Change since 1929. 1928. Magnetic declination (cast) . . .. 17° 42-4' +5-0' Magnetic horizontal force . . .. 0-22123 —3y Magnetic inclination . . . . .. —68° 17-6' — 0-3' Northerly component . . .. . . +0-21075 —13y Easterly component .. .. .. +0-06713 +14y Vertical component .. .. .. —0-55575 — 9y Total magnetic force . . .. ... +0-59817 + 8y The tabulated hourly values for 1929 are printed as for Peg Absolute, at Amberley Substation, where the absolute observations have been made. The adopted values of the differences between Peg Absolute and the piers of the Christchurch Absolute House have been assumed from various comparisons made, as follows, with the conventional signs for D(+), H(+), Z( —) : — Christchurch—Amberley : — Declination, east (+) ..' .. .. .. .. —2-7' Horizontal force (+) . . . . .. . . .. —242y Vertical force (—) . . . . . . . . .. —323y The Milne seismograph No. 16 has been kept recording, and a list of earthquakes recorded is being published. A complete set of Galitzin seismographs is being provided for this Observatory by the Department. The disastrous earthquake in the Buller district on the 17th June was specially reported on by myself and Mr. H. F. Baird, who visited the district. As usually happens after severe earthquakes, after-shocks from this earthquake still persist in that district. From our observations in the district definite lower limits for the actual horizontal acceleration in the main shock were determined to have been Jg. at Murchison, and Jg. at Bainhana, Golden Bay. A similar inspection and report was also made on the lesser shock, which did damage in the mountainous regions near Bealey on the 9th March. In order to enable pilot-balloon observations to be made daily on week-days, the staff of the Observatory has been reinforced by the addition of a cadet. For use in prediction, the results of the flights are telegraphed daily to the Director of Meteorological Services, Wellington. The usual thricedaily meteorological readings have been made, and besides having been tabulated here the results have been made available to the public through the daily papers. The Bensdorf electrograph has now been, housed in a small special building in the North Domain. Some tabulations and results of its records over fourteen months 1928-29 will be printed in Records of the Survey of New Zealand. The results of the observations for thirteen months have also been communicated to the Department of Terrestrial Magnetism, of the Carnegie Institute, Washington, D.C., U.S.A., and by request are being published in the Journal of Terrestrial Magnetism and Atmospheric Electricity in a forthcoming number. Some computations of observations in connection with the geodetic survey are being carried out at the Observatory. It is certain that this geodetic survey is destined to be of prime importance in determining the amounts of relative movement consequent upon seismic disturbance, and no doubt in some cases of those movements which actually preceded earthquakes. As yet repeated precise measurements seem to be the only way of identifying regions of varying strain where earthquakes

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