H.—34.

APIA OBSERVATORY, SAMOA. Director : J. Wadsworth, M.A. The observatory at Apia continued during the year 1937-38 its usual routine of work in geophysical subjects. Terrestrial Magnetism. The Godhavn balance and the Eschenhagen variometers of declination and horizontal force operated continuously except during a period of three months commencing in July, 1937, when the roof of the Gauss House was under repair. The kerosene burners of the recording lamps were replaced in April by electric bulbs taking current from the mains through a transformer. A test of the variometers for temperature compensation showed that we cannot annul completely the effect of temperature on the Godhavn balance ; but we were able to eliminate it almost completely in the variometer for horizontal force. The instruments used for absolute observations were magnetometer No. 9 C.I.W. (on loan through the courtesy of the Carnegie Institution of Washington) and the Schulze earth inductor No. 2. These instruments were standardized in June, 1937, on behalf of the Carnegie Institution by Mr. W. C. Parkinson. The revision of declination measurements for the period 1932-34 rendered necessary by the discovery in 1935 of a defect in the old Tesdorpf magnetometer has been satisfactorily completed. Seismology. The seismographs at Apia—namely, a Wiechert horizontal seismograph (mass 1,000 kilograms) and a Wiechert vertical seismograph (mass 80 kilograms) originally installed more than thirty years a g 0 —have been maintained in use during the year under consideration. The vertical seismograph was unsatisfactory until July, 1937, when Mr. Wadsworth introduced some slight modifications of design which have increased the sensitivity of the instrument and improved the scope of the records of all three components. In particular the instrument is able to record the vertical component of microseisms. The approximate geographical positions of five important earthquakes since July, 1937, were indicated by the records of the instruments at Apia alone, and in one example the depth of focus was correctly given as well. A swarm of small shocks of unknown origin were recorded in October, 1937. Meteorology. The routine work in meteorology comprises surface observations made twice a day and frequent measurements of upper winds. Climatological summaries are also prepared, and snyoptic charts of the weather in the south-west Pacific Ocean are plotted every day. New charts for synoptic work were introduced in September, 1937, having a scale of 1 : 20,000,000. The Piche evaporimeter was removed from its position on the veranda in November and placed in a small Stevenson screen.

Meteorological Summary, Apia, 1937.

122

Month. Pressure. j Temperature. Rainfall. Sunshine. j Wind. I Miles In. ° F. In. Per Cent. Hours. per Hour. January .. 29*74:4 80*2 15*20 80 220*7 7*4 February .. 29*779 80*3 15*85 81 151*5 7*6 March .. .. 29*769 79*3 16*15 81 187*2 5*9 April .. .. 29*814 1 80*0 9*41 80 212*2 6*3 May .. .. 29*872 79*0 15*59 77 218*0 7*5 June .. .. 29*867 78*8 0*65 76 j 245*7 7*9 July .. .. 29*861 79*0 2*02 76 259*7 7*8 August .. 29*861 78*8 6*26 78 223*4 11*0 September .. 29*902 I 78*4 5*46 74 ] 223*2 6*9 October .. 29*866 j 79*2 9*28 77 j 205*5 8*4 November .. 29*799 79*7 4*56 74- 225*1 5*8 December .. 29*767 j 79*7 11*17 76 192*5 5*4 Total 111-60 .. 2,564*7 Mean .. 29*825 j 79*4 .. 77 .. 7*3