Sessional_Paper_1885-1886 — Page 186

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maximum, which is the absolute maximum. The barometer stands comparatively highest at 10 a. in mid-winter. It then begins to fall and attains again its average value about 1 p., but later in summer than in winter. It reaches its second minimum between 4p. and 5 p. in summer, but already about P. in winter. At all seasons of the year this is the absolute minimum but comparatively lowest in winter. Thereafter it rises and reaches its third average shortly before 8 p. in winter and shortly after 8 p. in summer. The second maximum occurs about 10 p. This was comparatively highest in August. Then the barometer falls, attains its average value about 1 a. and a minimum about 4 a.

The diurnal range in the different months came out as follows: January, 0.100, February, 0.098, March, 0.095, April, 0.097, May, 0.087, June, 0.070, July, 0.065, August, 0.067, September, 0.074, October, 0.087, November, 0.105, December, 0.108. The average range was 0.088, exactly the same as in the previous year. .

The height of the rock on which the look-out at Victoria Peak is placed has been calculated from the mean of the barometric observations made in 1885 to be 1814 feet, and from the mean of those made in 1884 and 1885 to be 1816 feet.

The first column of the following table shows the mean height of the barometer reduced to Mean Sea Level at the Hongkong Observatory. The second column shows the mean excess of the barometer in Shanghai over that in Hongkong, the distance between these stations being about 670 miles. The third column shows the mean excess of the barometer in Hongkong over that in Manila, the distance being about 600 miles. The data in the two last columns have been derived from the telegraphic reports issued at 10 a. from the Harbour Master's Office, Shanghai, and from the Missionary Observa- tory, Manila, respectively

1885. January,.

February,.

March,

April,.

May,.

June,

July,

August,

September,

October,

November,

December,

Year,.

30.223

+ 0.094

+ 0.160

.153

+ .122

+ .150

.107

+

.031

+

.093

29.954

+

.013

.021

.877

.040

.039

.784

.041

.069

.736

.042

.122

.727

.011

.092

.864

.006

.038

30.023

+ .017

.089

.175

+

.050

+

.196

.154

29.981

+ 0.055

+ 0.169

+ 0,020 + 0.043

The comparison of this with the corresponding table in last year's report illustrates the comparative steepness of gradients for SW winds, which evidently was the cause of the typhoons nearly all passing East of Formosa..

In order to reduce the barometric readings to the gravity of latitude 45°, using Colonel Clarke's figures, the following corrections should be applied: Manila: -0.068, Hongkong: -0.055, Shanghai: -0.036 and in consequence + 0.019 should be added to the numbers in the second column and + 0.013 to those in the third.

Table II exhibits the mean temperature in degrees Fahrenheit at the Observatory and at the Peak, the latter being the mean of the 10 a, 10 p, maximum and minimum temperatures, and the excess of the hourly values at the Observatory above the mean. The daily variation is smaller in summer than in winter. The hottest part of the day is between 1 p. and 2 p. and the coldest about 6 a, but the lowest temperature occurs earlier in summer than in winter.

The diurnal ranges of temperature are exhibited in Table XVIII. The daily range of temperature is diminished by the circumstance that the force of the wind is smaller at night. It is on an average greater at the Observatory than at the Peak, the air at the former station having been somewhat longer in contact with the ground, which is heated during the day and cooled during the night through radiation. For this reason the daily range of temperature is greater in low places than in those exposed on prominences, a circumstance of some importance in selecting sites for camps, etc.

The monthly extremes of temperature are exhibited in Tables XVI and XVII. The ranges are much greater in winter than in summer.

Table III exhibits the relative humidity in percentage of saturation at the Observatory and at the Peak, the latter being the mean of the 10 a. 4 p. and 10 p. values, and the excess of the hourly values above the mean at the Observatory. The air is farthest from saturation and therefore feels driest between 1 p. and 2 p. and nearest saturation about 4 a., when it feels dampest. The average relative humidity is registered about 8a. and 6 p.