F 15
The Dent Mean Time clock (No. 39740) was used throughout the year for dropping the Time Ball, maintaining the electric time service in the Observatory, and sending hourly signals to the Railway, the Post Office, and the Eastern Extension Telegraph Co. The clock is corrected daily at about 10 a.m. by the electric regulating apparatus, and its daily rate kept below 0.5 sec. by the addition or removal of weights from the pendulum. It tripped 14 seconds on March 14, 12 seconds on November 20, and 22 seconds on November 21. It also tripped several times on December 23 and 24. The tripping on November 20 and 21 was caused by the driving weight suspension cord slipping from the pulley, and on the other occasions by undue pressure of the 2-second contact springs on the programme wheel.
The electric Sidereal clock was mounted in the computing room in a wood and glass case on January 9, and adjusted to keep Mean time. It gives a 2-second impulse to a dial in the computing room, and to another in the Director's room. The clock has performed excellently, and has proved invaluable as a check on the performance of the minute dials.
Chronometer Dent No. 40917 is on loan to the Cape d'Aguilar Wireless Station, and chronometer Dent No. 39946 to the Peak Signal Station. Chronometer Woolf No. 5232 was forwarded for safekeeping to the Observatory by the Hon. Colonial Treasurer in August.
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., Ld., through a Nodon valve. During March two Nodon valves of improved pattern and with larger electrodes were installed, those previously in use having become worn out. One of these valves is very satisfactory; the other is only efficient for very short periods.
Constantly recurring electrical faults led to a thorough examination of the electric installation by the Chief Assistant and Mr. Ovenden (of the Public Works Department). It was found that the earth return from the Time Ball was the cause of many of these faults; several defects were found on both the inner and outside circuits, and a defective main from the China Light and Power Company's system was discovered. These defects were remedied, and all earth returns abolished as soon as possible. All outside lines connected with the Observatory are now contained in an underground cable. In view of the leakage of alternating current to the clock and telegraph circuits the practice of using the battery during charging was discontinued, and the Fuller battery, hitherto reserved for the Morse instruments, was brought into use during the charging of the Tudor battery, and vice versa. One battery now supplies power for all requirements.
To give greatest effect to the new arrangements it was decided to embody them in as simple a manner as possible, on a new switchboard, and to renew all interior wiring. This was