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SUPPLEMENT TO THE HONGKONG GOVT GAZETTE OF 23RD FEB., 1884.
At Victoria Peak, the Instruments, except the Radiation Thermometers, are placed in the Look-out. The Barometer is about 1823 feet above Sea Level. The bulbs of tre Thermometers are about 4 feet above the floor, except the Maximum and the Terrestrial Radiation Thermometers, which are placed at the same height above the ground as at the Observatory.
At Cape d'Aguilar, the Thermometers are placed about 170 feet above Sea Level in a wooden screen 2 feet above the ground, except the Maximum Thermometer, which is a few inches higher.
No Instruments are used at Green Island.
Table I exhibits the readings of the Barometer reduced to 32°.0 Fahrenheit, but not to Sea Level, at the Observatory and at Victoria Peak.
The Mean Height of the Barometer at the Observatory was 30.093, and at the Peak 28.302 inches. The atmospheric tide can scarcely have appreciably exceeded 0.101 at the Observatory. The Baro- meter at the Peak was not read off with sufficient accuracy and is not sensitive enough for determining the atmospheric tide at that altitude. The highest reading of the Barometer registered at the Obser- vatory was 30.356 at 10 a., on the 8th and at the Peak 28.481 at 10 p., on the same day. The lowest reading was 29.856 at 4 p., on the 29th at the Observatory, and 28.116 at 4 p., on the 30th at the Peak. Table II and Table III exhibit the readings of the Thermometers (Fahrenheit) at the Observa- tory, Cape d'Aguilar and the Peak. The Radiation Thermometers had not been fixed at the Peak.
The Mean Temperature during the month was 62.4 at the Observatory, 61.4 at Cape d'Aguilar and 55.5 at Victoria Peak. The 29th was the hottest day, when the Temperature rose to 75.7 at the Observatory, 72.8 at Cape d'Aguilar and 69.1 at the Peak. The 9th was the coldest day, when the Temperature fell to 46.7 at the Observatory, 48.6 at Cape d'Aguilar and 38.0 at the Peak."
The Mean Temperature in Hongkong decreased one degree Fahrenheit for every 280 feet ascended. Table IV exhibits the Relative Humidity in percentage of saturation (the Humidity of air satur- ated with moisture being 100) as determined from observations of the Dry and Damp Bulb Thermo- meters. The Mean Relative Humidity at the Observatory was 76, at Cape d'Aguilar 874, at the Peak 87. The Least Relative Humidity registered at the Observatory was 34 at 4 p., on the 9th, at Cape d'Aguilar 38 at 10 p., on the 8th, at the Peak 37 at 10 p., on the same day.
Table V exhibits the Tension of the Aqueous Vapour present in the Atmosphere at the Observa- tory and at Victoria Peak, expressed in inches of mercury. The Mean Tension was 0.443 inches at the Observatory, 0.404 at the Peak. The Greatest Tension registered was 0.589 at 4 p., on the 24th at the Observatory, and 0.546 at 10 a., on the same day at the Peak. The Least Tension was.0.142
at 10 p., on the 8th at the Observatory, 0.124 at the same time at the Peak.
These figures show that the Tension decreased with the altitude of the Observer in Hongkong. Table VI exhibits the Direction (to two points) and Force of the Wind (0-12), and Sea Disturb- ance (0-9). The portion of the register, that refers to 4 a., as well as the Sea Disturbance registered at the other hours, has been derived from observations made at the Lighthouses.
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The Mean Direction of the Wind at 4 a., is registered as NE. At the other hours; from observations made at the Observatory, as E. But I am inclined to think, that the former Direction is vitiated from want of experience of the Observers. The Mean Force of the Wind was 3.0 correspond- ing to a velocity of 18 miles per hour. The Force of the Wind was greater during the night than during the day.
Table VII exhibits the Direction and Force of the Wind at Victoria Peak. The Mean Direction is E. and the Mean Force 4.0 corresponding to a velocity of 23 miles per hour.
Table VIII exhibits the Amount, Name and Direction whence coming, of the Clouds. When the Names of Upper and Lower Clouds are given, but only one Direction, this refers to the Lower Clouds. The Mean Direction of the Lower Clouds was E. The Mean Direction of the Upper Clouds cannot be stated, as their heights are so very different, but the observations clearly prove the existence of an upper counter-current from W. On an average 62 per cent of the sky was clouded. The Nebulosity was greater during the night than during the day.
No measurable quantity of Rain fell during the month at the Observatory.-Drizzling Rain fell the 1st at 4 a., the 2nd at 10 p.. the 10th at 4 p., the 13th at 10 p., the 25th occasionally during the afternoon and at 10 p.. the 30th at 1 a., 10a ., 4 p., and 10 p.,Duration about 8 hours, the 31st for 2 hours during the afternoon.-The total Duration of Drizzling Rain is estimated at 17 hours.
Fog prevailed extensively at Cape d'Aguilar and at the Peak. No Fog was registered at the Observatory, but the horizon was generally seen more or less hazy.
Heavy Dew fell at the Observatory during the night between the 16th and the 17th, and a Rain- bow was seen on the 13th at 5 p.