SUPPLEMENT TO THE HONGKONG GOV" GAZETTE OF 28тп MAR., 1885. 263
:... Hi-hthouses (marked Lh.) the force of the wind is greater than along the coast or at inland Bat it should be remembered, that the stations along the coast are generally in a more or e position.
erometric range increases with the latitude, - roughly speaking with the sinus of the perhaps more rapidly. This illustrates the fact, that a certain change in the barometer mich stronger wind in a southern than in a northern latitude
Latitude.
15°
21°
23°
25°
31°
38°
Monthly Barometric Range.
0.215
.266
.244
.276
.446
.560
.668
Force of Wind.
1.3
2.8
3.4
3.5
3.1
3.7
2.3
43°.
Table II shows the average temperature in degrees Fahrenheit at the Observatory and at the The latter being the mean of the 10 a. and 10 p. temperature, and the excess of the hourly values the mean. The daily variation was remarkably constant throughout the year, except in December it was greater owing to the clearness of the sky and the dryness of the air. The hottest part of day falls about 2p. in winter and about 3p. in summer. The greatest cold fell about 6a. Table III shows the relative humidity in percentage of saturation at the Observatory and at the Pak, the latter being the mean of the 10a. and 10p. values, and the excess of the hourly values above mean. The daily variation was remarkably constant except in December, when it was much ater than during the previous months. The air is farthest from saturation and therefore feels driest at 3p. and nearest saturation between 4a. and 6a. when it feels dampest. The average relative midity is registered between 8 a. and 9 a. and also about 7p.
Table IV contains the tension of aqueous vapour expressed in inches of mercury at the Observatory at the Peak, the latter being the mean of observations at 10a., 4p., and 10p. The daily variation, was to be expected from a coast station, is small, but there is less water vapour suspended in the in the morning than in the evening. Only in December, when the weather was very dry, did the daily variation amount to any noteworthy proportion. The decrease of aqueous vapour with increasing Light is smaller than that indicated by HANN's formula, especially in winter when the clouds are low, a during the SW monsoon, when the clouds are higher, the decrease agrees better with the formula. The vapour tension has a gradual annual variation, which is perhaps even greater than in Calcutta. E maximum fell in July, and its minimum in December, but it may he seen from Table. III, that the and Ir appears to be dampest in March, because then the air is almost saturated with water vapour,
decrease of temperature of the air, or of any object with which it comes in contact, causes a part the vapour to be precipitated in the form of dew.
Both the relative humidity and the vapour tension were calculated by the aid of BLANFORD'S tables. Table V exhibits the total number of hours of sunshine registered. There. was more sunshine ring the afternoon than during the forenoon. The amount increased and reached its maximum in ember, although then of course the possible duration is a minimum. The actual minimum of shine occured in March and the change from maximum to minimum is abrupt.
Table VI exhibits the velocity of the wind expressed in miles per hour and the excess of the Bourly values above the mean. The velocity at the Peak has been calculated from the force estimated re at 10a., 4p., and 10p. The usual daily variation of the velocity of the wind with its maximum ut mid-day is seen at a glance, and the variation appears to be greater in summer than in winter. During the first months of the year there appeared to be a maximum in the early morning hours, as inted out in the monthly weather reports.-The annual variation of the velocity of the wind is also t. The wind is stronger in winter than in summer. The velocity of the wind at the Peak, even ing into consideration that it is observed principally during the day, is much greater than near sea vel, and the annual variation is not so well marked. The secondary minimum of wind force in May Well known to mariners, and also shown by the sea disturbance in Table XIII, is scarcely noticed the Peak. But different questions arising from this comparison will scarcely be answered till a -recording anemometer is erected at the Peak.
On an
Table VII shows the mean direction of the wind at the Observatory and at the Peak. ge the direction is a point more southerly at the Peak. The excess of the hourly direction above can, expressed in degrees, has been counted from North through East towards South. The ing of the wind during the day is scarcely remarked except during the southerly monsoon, and in August was it prominent.-Already DAMPIER pointed out the comparative absence of land and freezes on cast-coasts, but KÖPPEN has lately propounded an hypothesis, according to which the ase and the veering of the wind during the hottest part of the day should be caused by the descent The colder air from above, the velocity of which is greater and the direction of which is seen to be
southerly.