- F 13 -
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.
The number of observations in the years 1919 and 1920 were as follows:-
1919 1920 Transits, 1,321 985 Level determination, 676 557 Azimuth, 23 20 Collimation, 22 20Transits of the Sun were utilized occasionally during 1920. The azimuth and collimation determinations were made by the Chief and First Assistants from observations of the old south mark.
Clocks. The losing rate of the Standard Sidereal clock, Dent No. 39741, varied from -0.23 sec. on July 9 (Barometer 30.63 Temperature 84.3) to -0.76 sec. on November 11 (Barometer 29.82 Temperature 78.3).
The rate during cloudy periods was usually derived from the formula :-
r = -0s 792 + 0s 575 (b-29ins) + 0s.00021 (t-50°) where r is the computed losing rate, and b and t the mean barometric pressure and temperature, respectively, for the preceding 24 hours.
In the following table is given the excess of the observed over the computed error after cloudy periods during 1920—
Date 1920. Interval without observations. Excess of observed over computed error. February 16, March 18, 22 days +1.01 March 24, 3 +0.28 April 2, 3 0.32 April 16, 12 +0.31 May 10, 18 +0.58 May 18, 6 +0.51 June 2, 7 0.09 June 16, 6 0.26 June 27, 5 +0.49 July 5, 4 0.42 July 23, 6 +0.35 August 6, 8 0.10 August 12, 4 +0.04 August 20, 4 0.19 September 1, 8 +0.43 September 14, 3 +0.11 September 21, 3 0.56 September 24, 3 0.45 October 9, 4 0.36 November 8, 4 +0.35 December 2, 5