- F 17 -
The Mean Time clock (Dent No. 39740) was in use until November 30, for dropping the Time Ball, maintaining the electric time service in the Observatory, and sending hourly signals to the Railway, the Post Office, the Telephone Co., and the Eastern Extension Telegraph Co. The clock is corrected daily before 10 a.m. and before 4 p.m. by the electric regulating apparatus. The daily rate of the pendulum is kept below 0.5 sec. by the addition or removal of weights.
Since December 1, Mean Time clock (Leroy No. 1350) has been used for the above purpose. This clock was received on September 23, and operates the time service through two dials with half-second pendulums which it effectually drives and synchronises by means of an electric impulse each second. It also actuates an apparatus for emitting Radio time signals in accordance with the new International System (See Government Notification No. 637 of 14.11.24).
The Brock clock was mounted in the seismograph underground room on January 10, for use in connection with the seismograph.
Chronometer Dent No. 40917 is on loan to Stonecutters Radio Station, and Dent No. 40912 is on loan to the P.W.D. Radio Station at the Observatory.
Batteries, Power Supply, &c.-The necessary current for the Time Service has been supplied by accumulator batteries, charged as found necessary from the alternating mains of the China Light and Power Co. Ltd., by a rotary converter. The Tungar rectifier and 3 Delco Cells are on loan to the P.W.D. radio station at the Observatory.
IX.-MISCELLANEOUS.
Seismograph.-149 earthquakes were recorded during the year by the Milne-Shaw Seismograph, as against 141 in 1923. The seismograms have been forwarded to the President of the Seismological Committee, Oxford. A slight earthquake shock was felt at 10:45 p.m. on January 10.
Upper Air Research.-49 flights with pilot balloons were made during the year. The results of the observations have been sent to the Commission International pour l'exploration de la haute atmosphère, Kristiania.
Flying Officers Martin and Isaacs of H.M.S. Pegasus visited the Observatory on December 1 and 12 and kindly furnished copies of temperature observations made during four flights over Hongkong. The results are shown graphically on two charts appended to this Report.