H.—34.

MAGNETIC OBSERVATORY, CHRISTCHURCH. Director : H. F. Skey. SUMMARY OF OPERATIONS IN 1935. During the year the usual magnetic, seismological, and meteorological observations have been carried out. Additional observations have also been made since last January to assist in forecasting for aviational purposes. Terbestkial Magnetism. The Eschenhagen magnetographs at Amberley Sub-station have been kept recording continuously, and the resulting magnetograms have been developed, &c, and measured for mean ordinates during every Greenwich hour. The ordinates have been reduced, and, by the aid of twice-monthly absolute magnetic observations at the sub-station, the mean hourly values have been calculated. Any short occasional failure of the Eschenhagen records has been made good by the help of the Adie D and H magnetograms. In May the Adie instruments were removed to Amberley and installed in the underground chamber there. Calculated from these mean hourly values, the mean monthly values obtained for 1935, Amberley, are :— Mean Monthly Values of the magnetic elements from hourly mean values (all days), 1935, at Amberley Sub-station : — 1935. D. H. Z. January .. .. .. 18 04-7 22324 y -55219y February ~ .. ..18 05-2 22319 55218 March .. .. .. 18 05-0 22310 55213 April .. .. .. 18 05-8 22311 55217 May .. .. ..18 05-8 22317 55224 June .. .. ..18 06-1 22318 55224 July .. .. .. 18 06-9 22317 55226 August .. .. '... 18 07-2 22323 55223 September .. .. ..18 07-3 22310 55225 October .. .. .. 18 06-8 22312 55229 November .. .. .. 18 07-0 22320 55232 December .. .. ..18 07-7 22319 55233 Year .. .. ..18 06-3 22317 55223 A from 1934 .. .. +3-4 -14-6y + 6-3y (Numerical decrease). Y. X. T. 6 Year .. 06935-2y 21211-7 y 59562-3y -67°59'-73 A from 1934 +16-ly -20-9 y -11-3y -O'-66 The secular change in the magnetic elements has been somewhat greater than during the previous year ; sunspottedness is now approaching its epoch of maximum. Improvements have been made to the Amberley Sub-station, and some necessary repairs have been made to the Observatory buildings at Christchurch. Seismology. During the year there have been recorded 191 seismic disturbances at Christchurch. In February, 1936, the Galitzin seismographs and the Wood-Anderson seismograph were removed to the underground cellar, formerly occupied by the Adie recorders. The Galitzins have continued to record with equal magnification on all components, and constants have been determined at intervals. Provisional monthly bulletins were issued promptly to the Dominion Observatory, Wellington, and to co-operating stations overseas. Wood-Anderson records have been lent regularly to the Dominion Observatory. They have been of considerable assistance here in interpreting other records. It is hoped in the near future to acquire a Benioff vertical seismometer, with both long- and short-period galvanometers, to help more especially in the interpretation of results of Wood-Anderson recordings. From 31st July, 1935, to Bth February the assistant, Mr. H. F. Baird, was relieving Mr. Wadsworth, Director of the Apia Observatory, Western Samoa. The Carnegie Institute of Washington has sent to Christchurch one of its continuously recording cosmic-ray meters. This has been housed in a special insulated building near the Observatory and is functioning well. The usual programme of atmospheric potential-gradient observations was continued satisfactorilv.

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