65

H.—34

Publications. The following Observatory publications have been issued during the year : —• Bulletin No. 68.—" Interpolation," by C. E. Adams. Bulletin No. 69.—" International Longitude Determinations, 1926." Bulletin No. 70.—" Reception of Wireless Time Signals at the Dominion Observatory, Wellington." Bulletin No. 71.—•" Tables of Geodetic Factors for use on the Brunsviga Calculating-machine," by C. E. Adams. (Extract from the " Transactions of the Australian Association for the Advancement of Science.") Bulletin No. 72. —" The Orbit of the Comet, 1927!%" by P. W. Glover. (Reprinted from the " Transactions of the New Zealand Institute," vol. 59, part 3, September, 1928.) Bulletin No. 73.—" Earthquakes in New Zealand." Bulletin No. 74.—" Solution of Euler's Equation in a Parabolic Orbit," by C. E. Adams. (Reprinted from Astr. Nachr. Nr. 5617, Band 235, Marz, 1929.) Bulletin No. 75.—" Report of the Department of Scientific and Industrial Research." Bulletin No. 76. —" New Zealand Time Service Arrangements." E.-12.—Earthquake reports for 1927, February. E.-13.—Earthquake reports for 1927, March to May. E.-14.—Earthquake reports for 1927, June to August. E.-15.—Earthquake reports for 1927, September to December. As in past years, the Observatory is again indebted to individuals and to institutions for valuable gifts of publications. Some of these are presented in exchange for the bulletins. APIA OBSERVATORY. REPORT BY THE DIRECTOR (MB. A. Thomson). In July, 1928, the control of the Apia Observatory was transferred from the Department of External Affairs to the Department of Scientific and Industrial Research. This change was brought about through the general policy of co-ordination of scientific effort in the Dominion. The general programme of geophysical investigation which has steadily gone on since the founding of the Observatory in 1904 has continued without alteration. The valuable co-operation of the Carnegie Institution of Washington and the British Admiralty has been retained under the new administration. The activities of the Observatory are concerned with terrestrial magnetism, seismology, and meteorology. In these subjects the Apia Observatory has a fundamental duty of supplying information for the South Pacific Ocean, in which no other well-equipped station exists. The chief results obtained will now be reviewed. Terrestrial Magnetism. In terrestrial magnetism hourly values have been determined of the horizontal component of the earth's magnetic field. The mean annual value derived therefrom was 35,225 gamma, a slight increase from the previous year. The horizontal magnetic field has decreased consistently from 1904 until 1922, losing in eighteen years 1-2 per cent, of its original value. It would now appear to have started to increase. The declination showed an increase of 2-6 minutes of arc, the mean value for the year being 10° 32-I'. The magnetic needle has turned slowly but consistently towards the east since 1904. The easterly movement for 1927 was slightly more than the average. The number of magnetically disturbed days during 1928 was higher than any other year since the present scale was adopted in 1921. Prior to 1921 the Observatory was under other auspices, so that the records cannot be directly compared. From its place in the sun-spot cycle, the year 1928 was expected to be a year of maximum sun-spots. In the low latitude of Samoa the variation in horizontal force during a magnetic storm is very pronounced. Measurements of the range and especially careful determination of the time of the sudden commencement of the storms were made. Seismology. Approximately three hundred earth-movements were recorded at Apia during 1928. The seismological equipment consists of a large Wiechert seismograph with a ] ,000 kgm. stationary mass for recording horizontal movements and a small 180 kgm. seismograph for vertical earth-movements. During the year the seismographs were adjusted so that the horizontal earth-movements were magnified about 125 times and the vertical movements about 40 times. Of the three hundred recorded earth-movements almost two hundred occurred within 50 miles of Apia. Despite the tremendous volcanic activity on Savaii, from 1904-11 no earthquake shocks of even the slightest intensity originated there during the year. A considerable number of shocks had epicentres between Niue Island and Vavau. Several subterranean volcanic eruptions in September and October are believed to have been accompanied by earthquakes of moderate intensity. Enormous quantities of pumice-stone were set adrift at this time. Ships reported great floating patches from near the equator as far as 20° S. latitude, and from 175° W. to 175° E. longitude. Preliminary analyses of fifteen earthquakes were made within a day of their occurrence and the results sent by radio to the United States Coast and Geodetic Survey. In addition, a quarterly report of all earthquakes recorded was published and distributed to about eighty institutions.