F 15
the installation of the Cottingham clock and the improved reception of radio time-signals. Apart from any intrinsic merits of the Cottingham escapement, the mounting of the clock under conditions of least change in pressure and temperature tends to produce steadier rates than has been possible with the Dent Sidereal hitherto.
The regular observation of the Nauen radio time signal at Sa... has proved an invaluable check upon clock performance. The signal consistently maintains a high degree of accuracy, and, assuming regular reception, accumulated clock errors of any magnitude over cloudy periods are now unlikely. It is therefore of extreme importance that radio time signals of undoubted accuracy should continue to be regularly received here, as cloudy periods are occasionally of considerable length.
The Mean Time clock, Leroy 1350, was used 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 withdrawal of weights, Mean Time clock Dent, 39740, has been corrected daily and its rate regulated as in the case of Leroy 1350.
Chronometer Dent No. 40917 is on loan to Stonecutters Radio Station.
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 the rotary converter or the Tungar rectifier; the latter having been returned by the P.W.D. early in the year.
IX.-MISCELLANEOUS.
Seismograph.-159 earthquakes were recorded during the year by the Milne-Shaw Seismograph, as against 149 in 1924. The seismograms have been forwarded to the President of the Seismological Committee, Oxford.
Upper Air Research.-40 flights with pilot balloons were made during the year. On September 25 the balloon was observed for 131 minutes, and on September 24 for 90 minutes. I imagine the former is one of the longest observed flights on record. The results of the observations have been sent to the Commission International pour l'exploration de la haute atmosphère, Oslo, (Kristiania).
F 15
the installation of the Cottingham clock and the improved recep- tion of radio time-signals. Apart from any intrinsic merits of the Cottingham escapement, the mounting of the clock under con- ditions of least change in pressure and temperature tends to produce steadier rates than has been possible with the Dent Sidereal hitherto.
The regular observation of the Nauen radio time signal at Sa.. has proved an invaluable check upon clock performance. The signal consistently maintains a high degree of accuracy, and, assuming regular reception, accumulated clock errors of any magnitude over cloudy periods are now unlikely. It is therefore of extreme importance that radio time signals of undoubted accuracy should continue to be regularly received here, as cloudy periods are occasionally of considerable length.
The Mean Time clock, Leroy 1350, was used for dropping the Time Ball, maintaining the electric time service in the Obser- vatory, 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 withdrawal of weights, Mean Time clock Dent, 39740, has been corrected daily and its rate regulated as in the case of Leroy 1350.
Chronometer Dent No. 40917 is on loan to Stonecutters Radio Station.
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 the rotary converter or the Tungar rectifier; the latter having been returned by the P.W.D. early in the year.
IX.-MISCELLANEOUS.
Seismograph.-159 earthquakes were recorded during the year by the Milne-Shaw Seismograph, as against 149 in 1924. The seismograms have been forwarded to the President of the Seismological Committee, Oxford.
Upper Air Research.-40 flights with pilot balloons were made during the year. On September 25 the balloon was observed for 131 minutes, and on September 24 for 90 minutes. I imagine the former is one of the longest observed flights on record. The results of the observations have been sent to the Commission International pour l'exploration de la haute atmosphere, Oslo, (Kristiania).
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