H.—34.

APIA OBSERVATORY, SAMOA. Director : J. Wadsworth, M.A. (Cantab.). The programme of work in geophysical subjects was maintained during the year 1932-33 as in previous years. Terrestrial Magnetism. Absolute measurements of the elements of the earth's magnetic field were made from time to time with the origina] Tesdorpf magnetometer and the Schulze earth inductor. Continuous records of declination and horizontal intensity were obtained by means of Eschenhagen variometers. There were no continuous records of the vertical intensity until a new Godhavn balance arrived in December, 1932. The Tesdorpf magnetometer was thoroughly overhauled in February, 1933, and the verniers were adjusted. An auxiliary reference-mark for the magnetometer was established on the wall of a small concrete-hut situated in the grounds of the Observatory. Mean values of the magnetic elements for all days during the past three years are given in the table which follows : —

Annual Mean Values of Magnetic Elements at Apia.

Seismology. The seismographs are of Wiechert design. Both instruments have been overhauled during the year, the vertical seismograph in particular having been idle for some time owing to a defect in the driving-mechanism. A new time-marking unit was installed on the horizontal seismograph in November, 1932, which has much improved the registration. The following analysis shows the character of the records of earthquakes obtained during the period Ist April, 1932, to 31st March, 1933 :— The total number of shocks registered at the Observatory was 186. Of them, 3 originated at distances within 1° of Apia, 136 between 1° and 9°, 11 between 9° and 45°, and 5 at distances beyond 45°. The distances of origin of the remaining 31 shocks were indeterminate. The intensity of 23 of the recorded shocks was sufficiently great to be perceptible to ordinary residents in Samoa. The epicentres of the more prominent earthquakes during the year are distributed as follows: Central America, 3 ; New Zealand, 3 ; Samoa, 2 ; Dutch East Indies, 1 ; Fiji Islands, 1 ; and Japan, 1. Meteorology. The work in meteorology included surface observations twice a day, as in previous years, and some measurements of upper winds from time to time using pilot balloons. The tail method was generally used with the pilot balloons, but frequently, owing to unsuitable elevation of the balloon in light winds or bad visibility of the tail, the computation had to be performed assuming a constant rate of ascent. A daily report of weather in the South Pacific has been displayed at the Post Office and customshouse since May, 1932, at the request of local traders. New meteorological instruments brought into use during the year are as follows : An aspirator bottle providing a constant supply of slowly dripping water to the wet-bulb thermometer ; a Snowdon type rain-gauge (Meteorological Office, London, pattern) as a check on the older German gauge ; two Stevenson screens of standard pattern devoid of the auxiliary protection once considered to be essential in the tropics ; a new hygrograph replacing the old one, which was worn out; a Gendle balance for filling pilot balloons ; a Fineman nephoscope from the Meteorological Office, Wellington, for which a permanent wooden pillar was erected ; a new Fortin barometer (by Casella), which arrived in November, 1932. The number of local rainfall stations increased to about fourteen during the year. The value assumed for the height of the barometer cistern at Niue Island was found to be in error, and fresh measurements made in September, 1932, gave 65 ft. One of these measurements is due to the courtesy of the Commander of the " Maui Pomare." During the visit of H.M.S. " Laburnum "to the Tokelau Islands in July, 1932, the Officer Commanding kindly arranged an inspection of the meteorological instruments there. The afternoon reports from Tonga failed temporarily dining the wet season, but were resumed in January. A tree fell on the Stevenson screen at Nassau Island and broke the thermometer and the thermograph. Several cyclones occurred in the South Pacific during the wet season, and warnings were issued from Apia in January, February, and March, 1933.

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1930 (Six Months). 1931. 1932. Declination E., 10° 34'-2 E., 10° 85'-2 B., 10° 36'-5 Horizontal intensity .. .. 35195gamma 35171 gamma 35116 gamma. Vertical intensity .. .. 20428 gamma 20434 gamma* 20460 gamma.* ♦ From absolute observations only.