Appendix F.
REPORT OF THE DIRECTOR OF THE ROYAL OBSERVATORY, HONGKONG, FOR THE YEAR 1921.
I. GROUNDS AND BUILDINGS.
The grounds were kept in order by the Botanical and Forestry Department with the assistance of the Observatory coolies.
The old magnetic hut was pulled down early in the year and quarters for the European assistants built on the site. They were completed in September.
II. METEOROLOGICAL INSTRUMENTS.
Barometers. - The glass tube for the Marvin compensated syphon barometer was received in December and the instrument set up in February, 1922. The circuit for the seismograph minute time break apparatus is led through two contact springs on the face of the barograph clock. When the minute hand arrives at 59 minutes it breaks this contact and makes contact for one minute through a third spring placed above the other two. The current instead of passing through the seismograph time-break coil thus passes through the coil of an electric hammer which time-scales the barogram every hour. Diverting the current from the seismograph at the 60th minute also serves to identify the minute breaks on the seismograms.
Beckley Anemograph. - This instrument was oiled and the orientation of the vane checked once a month.
Dines-Baxendell Anemograph. - The bearings of the vane were oiled and its orientation checked once a month. The spindle of the float was cleaned and oiled once a week. In November the instrument was carefully calibrated at low velocities by a pressure gauge constructed locally. The gauge was tilted about 80° from the vertical in order to obtain a measurable displacement of the water for a velocity as low as 5 miles an hour. The observations indicated that the float was too light; shot were therefore placed in the cup on the spindle until the float sank to the correct level. The criterion being that the line produced through the observations of the pressure gauge, plotted against the corresponding pressures read from the anemogram, should pass through the zero of the anemogram scale.
The mean monthly results of comparisons with the records of the Beckley Anemograph from 1910-1920 are given in the following table, together with the results for 1921,