H.—34.

Owing to various causes, the records of some of the stations are not complete for the whole year. Owing to a series of breakdowns, the East Cape seismograph|was recording only fromjJanuaryjto April. The Rotorua station was not established until 27th November, so #| that no records are available prior to that date. The Jaggar station at New Plymouth (Class II) was ti dismantled k in November ; and the Wood-Anderson records at that station were interruped from 14th October to 15th November, owing to clock trouble. The seismograph at Bunnythorpe|was out of action from Ist May to 30th June, and from 13th July to 30th September owing trouble. ImamuraJ strong-motion seismograph at Takaka was under overhaul during January and February. Early in' June this seismograph was transferred to Wellington, and was replaced by a Jaggar. On account of this change in instruments, the Takaka records were interrupted during June and July. During March and April the Chatham Islands seismograph was not recording, owing to illness of the observer ; and the Christchurch Wood-Anderson records were interrupted from Bth to 22nd January, and from 18th to 31st August, owing to repairs being made to the driving clock. } During the year 1936 steps were taken to improve the timing at some of the stations.§§ In September a chronometer, fitted with minute contacts, was despatched to New Plymouth for supplying accurate timing on the Wood-Anderson seismograph there. Time marking, usually accurate to the nearest second, was thus made available on the three Wood-Anderson seismographs, located respectively at New Plymouth, Wellington, and Christchurch. This should provide more satisfactory data for the study of local earthquakes and problems relating to local crustal structure. Additional stations are to be provided with chronometers in the near future. Research Work. —Seismologieal research work carried out during 1936 included some investigations into the occurrence of destructive earthquakes, as connected with pole-shift, and the application to New Zealand earthquakes of Dr. C. P. Richter's method of expressing the magnitude of local earthquakes in accordance with the maximum amplitudes recorded on Wood-Anderson seismographs. Mr. W. M. Jones carried out some work on the geographical distribution of earthquake epicentres in the New Zealand region, and their association with geological faults. Mr. Jones also commenced a detailed study of the records of local earthquakes, with a view to obtaining further information on the local crustal structure. Dr. L. Bastings and Mr. K. E. Bullen have been working voluntarily on various seismologieal problems, in co-operation with the Observatory. The Observatory is grateful to the officers of other Government Departments, and private individuals, who have assisted in the seismologieal work by operating instruments and forwarding records and reports of earthquakes. General. Geodetic Work. —On 24th September the Public Works Department erected a concrete post on the Tinakori Hills, to act as a north meridian mark for the transit instrument. Systematic observations of this new meridian mark and of the existing south meridian mark were commenced, in order to provide data for the detection of local land movements. Tilting of the ground at the Observatory is measured by the Milne-Shaw seismographs, and by the level on the transit instrument. It is not expected that any definite movements due to geological causes will be detected until these observations have been in progress for several years. In this branch of the Observatory's work, the co-operation of the Lands and Survey Department, the Wellington City Council, and the Wellington Harbour Board, has been sought. Geophysical Work. —During the latter part of the year officers of the Observatory carried out geophysical survey work as follows : Mr. C. N. M. Watson-Munro was engaged, in seismic refraction observations in the Masterton valley from 24th November to 4th December, in connection with water-supply investigations. During the period 23rd November to 29th December, Mr. W. M. Jones was engaged in geophysical and geological work in the Tokotoka-Paparoa district, and in geophysical work in the Rotorua-Waiotapu area. Publications. Commencing with May, 1936, the quarterly seismologieal reports and the monthly preliminary seismologieal reports were replaced by a monthly cyclostyled report, giving complete seismologieal data from all the New Zealand stations, and including a separate provisional bulletin prepared by the Director of the Magnetic Observatory, Christchurch. These reports are published as promptly as possible, and distributed to the chief seismologieal observatories and institutions throughout the world. During the year 1936 preliminary reports were published, for 1935 (December), 1936 (January, February, March, April), and full reports for 1936 (May to November), (inclusive). The latter reports consist of monthly Bulletins E5O, E5l, E52, E53, E54, E55, E56. Seismologieal reports for the whole of the years 1934 and 1935 were published as quarterly Bulletins E4O, E4l, E42, E43, E44, E45, E46, and E47. The following Observatory Bulletins were also published during 1936 :— Bulletin 96.—Mean Time and Time Service (from the " New Zealand Official Year-Book "). Bulletin 101. —Seismic Waves and Crustal Structure in the New Zealand Region. (R. C. Hayes.) Bulletin 105. —Report of the Dominion Astronomer and Seismologist (C. E. Adams) for the year ending 31st December, 1934. Bulletin 106. —Some Seismologieal Aspects of the Buller Earthquake : Part 11, the P Waves in the Distant Hemisphere. (L. Bastings.)

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