F 13
The ball was dropped successfully 334 times. There were 11 failures, 3 of which were caused by the negligence of the computers in charge at the tower, who were fined. The remainder were due to electrical and mechanical defects. The days on which the ball failed to drop were:- January 22, March 23, May 3 and 10, June 22, July 1, 5, 8, 10, and 20, and December 7. It was dropped at 14h on January 22, July 6, and December 7, and at 15h on July 10.
The ball was not raised on July 4, 26, and 27, owing to high wind. The apparatus was in course of repair, or adjustment, on February 4, 5, 6, June 14 and 24, July 2, 6, and 7, August 26, and September 3 to 10.
The ball fell with an error of 0.3 sec. or less on 299 occasions, and with an error of 0.4 sec. or 0.5 sec. on 29 occasions. Errors of 0.6 sec. occurred 4 times, of 0.7 and 0.8 once each. The mean probable error of the Time Ball was ±0.15 sec. The monthly values for the past 5 years are given below:-
Month 1915 1916 1917 1918 1919 January +0.17 0.17 +0.1 +0.24 February *0.44 •0.28 0.10 0.13 *0.20 March 0.17 *0.17 *0.15 *0.12 April *0.38 *0.18 *0.18 '0.10 *0.19 May *0.16 :0.16 0.17 *0.12 0.14 June *0.15 0.17 '0.10 0.14 0.14 July *0.17 *0.10 '0.21 '0.11 0.13 August 0.15 0.10 *0.26 0.15 0.13 September *0.11 0.10 '0.11 0.10 0.16 October '0.10 0.13 *0.10 *0.12 *0.15 November 0.16 0.13 0.10 '0.12 0.14 December 0.14 '0.11 *0.10 0.14 *0.12 Means +0'19 ±0.14 +0'13 +0'14 +0'15Time Signals by Wireless Telegraphy. In addition to the time signals given by the Time Ball at 13h, signals are sent at noon and at 21h by wireless telegraph via Cape d'Aguilar. Particulars of the programme are given in the 1918 Report. The service has been interrupted rather frequently by circumstances over which the Observatory has no control.
Wireless Receiving Set.-Mr. Henké, the officer detailed by the Naval Authorities to superintend the installation of a wireless receiving set at the Observatory, up to the time of his departure, in July, had not succeeded in obtaining time signals from Shanghai or Manila. Commander R. R. Cooke, R.N., is now reporting on what should be done to obtain these signals.
Transit Instrument. Observations for time were made daily with the 3-inch transit instrument and the Hipp tape chronograph by the Chinese computers, weather permitting.