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to other centres and also punched onto cards for climatological purposes.
One of the most important functions of the central forecast office is to issue warnings of tropical cyclones. Whenever a tropical depression, tropical storm or typhoon is located within the region bounded by the latitudes 10° and 30° north and the longitudes 105° and 125° east, six-hourly or three-hourly bulletins are issued. These include information on the storm's intensity and expected development, the position and movement of its centre and the forecast position for 24 hours ahead. Reliable reports from ships and storm reconnaissance aircraft help to locate storms accurately. When the Colony itself is threatened, the local storm warning system is brought into use and warnings are widely distributed by means of visual signals, telephone, radio and Rediffusion. While gale signals are hoisted statements are issued and broadcast at 30-minute intervals.
Time Service and Seismology. Time signals originating at the observatory are sent out over Radio Hong Kong for the public, and in special broadcasts for aviation and shipping. A visual time signal is flashed from the observatory's signal mast and various signals are provided for time marking seismograms and other pur- poses. The observatory operates six seismometers, three of which are on loan from the Lamont Geological Observatory. A weekly report giving arrival times of significant earthquake waves is sent to the United States Coast and Geodetic Survey and detailed analyses are later published and sent to other scientific institutions. The results are included in the International Seismological Sum- mary and in the bulletin of the International Union of Geology and Geophysics.
The observatory also participates in the Pacific Tidal Warning Service by sending telegrams to Honolulu Magnetic Observatory whenever severe earthquakes are recorded in Hong Kong. An exceptional number of at least 10 minor earth tremors were felt by residents of Hong Kong during the year. The most severe occurred on 19th March, but no serious damage was reported. All the tremors originated from earthquakes centred in an area about 80 - 100 miles north-north-east of Hong Kong.
Radioactivity. The Royal Observatory monitors the general level of radioactivity in the Colony by making routine measurements of