H.—34.

MAGNETIC OBSERVATORY, CHRISTCHURCH. Director : H. F. Skey. SUMMARY OF OPERATIONS FOR THE YEAR ENDED 31st MARCH, 1938. During the year the usual magnetic, seismologicai, and meteorological observations have been made. Terrestrial Magnetism. The Eschenhagen magnetographs at Amberley Substation and the high-speed La Cour and the Adie magnetographs have been kept recording continuously. From hourly measurements of the magnetograms and twice monthly absolute observations the mean hourly values of D, H, and Z have been collected and tabulated. The mean monthly values of the magnetic elements obtained from the mean hourly values for all days for 1937 are : — 1937. D. H. Z. O / January .. .. 18 12-2 E. 22305y —55204y February .. .. 18 12-3 22289 55208 March .. .. 18 12-6 22280 55201 April .. .. 18 13-3 22270 55199 May .. .. 18 13-9 22271 55212 June .. .. 18 14-1 22283 55226 July .. .. 18 14-5 22286 55215 August .. .. 18 14-9 22281 55218 September .. .. 18 15-4 22288 55208 October .. .. 18 15-2 22268 55208 November .. .. 18 14-9 22284 55189 December .. ..18 15-7 22288 55194 Year .. ..18 14-1 22282-7 55207-2 A from 1936 .. .. +4-2 —18-5y +12-7y (numerical decrease). Y XT (f) Year .. .. 06972-5y 21163-8y 59534-3y -68° 01' -20 A from 1936 .. .. +19-9y -26-ly -18-0y -o'-74 The rate of mean annual change, or secular change, is somewhat larger than for the previous year. The increase of sun-spottedness has continued, and at present the indications are for a high maximum. In response to requests, a large amount of data has been got out and sent to overseas investigators and others in connection with magnetic storms during the year. To improve local observations a Synchronome clock has been provided for the Observatory, and is performing well. It has been found that there is a decided diurnal variation in the variability of H within the hour here. Special tabulation of this has been made for ionosphere research. A minimum at 10 h. a.m. (N.Z. summer time) and a maximum at 16 h. to 18 h. have been shown to exist, with a secondary maximum at Bh. a.m. and a maximum rate of increase just before noon. It seems impossible to ascribe this to anything else than variation of ionization in the higher atmosphere, and it seems very desirable that continuous recording of the virtual heights of reflecting regions in the ionosphere should be carried out. It is understood that preparations are being made for this. The Bendorf electrometer has been kept continuously recording. Cosmic-ray observations have been continued successfully, and variations with certain magnetic storm effects have been detected. Research on microseisms is proceeding.

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