5
135
national use.
They are cum-cir, for sm-cum, str-cir, for very high str, a common fine weather cloud in Ireland, which had not hitherto been separately denominated, and str-cum, for Roll-cum (in Hongkong str-cum is used in a different sense). Cum-nim is also used, but is defined as nim of rounded shape, while any cloud from which rain is seen falling is called nim. in Hongkong. Cum-str is classed among rare and transient forms, whereas it is really common and even characteristic of certain regions such as the Malacca Straits. An uniformly covered sky is always entered as str in Hongkong. There are some strange explanations given in the same pamphlet such as on page 7, where it is said that cumulus may be formed by "collision between winds, such as land and sea breezes." The distinction "between the direction of propagation of a cyclonic cloud bank and the direction of motion of the clouds within the bank" is claimed as a new feature, whereas it is well known to practical meteorologists more especially within the tropics, where typhoons are observed, approaching in the first instance in the shape of an arch of dark cloud whose direction of motion forms an angle with the direction of the top of the arch. This has been thoroughly explained by FERREL a long time ago.
24. From an examination of thunderstorms in the Colony during the past five years it appears that they are most frequent in May and that they have not occurred in November, December and January. They seldom happen in February. With reference to the daily variation they are more frequent at night than during the daytime in the proportion of 3 to 2. They appear to be most abundant about la. and least so about 8a. in the proportion of about 2 to 1.
25. During the past year the temperature was on an average higher than in previous years and rose higher than before on hot days. This appears to have been at least partly due to a more south- erly direction of the wind, but indeed the temperature has been rising on the whole since 1884. Whether this is periodical remains to be investigated. There seems fair prospects of finding that it is So. It should be remembered that great care is taken with our thermometrical observations and the results are accurate in proportion. The past year was more damp than usual, the rainfall was heavy and the mean barometer below the average. The amount of sunshine was less and the cloudiness greater than usual. It is generally considered to have been an unhealthy year.
26. The weather in January, 1888, was very warm and dry. There was a great deal of dew but hardly any rain. Dry weather haze was common, but indeed dry haze is always common along the China coast during the NE monsoon. February set in very cold. The water froze at the Peak on one or two nights. Thunderstorms began early and were severe in March. During April the weather was very trying to the health. For the greater part it was overcast, damp and foggy. The end of April was unusually hot. There was a great fall of temperature in the afternoon on the 22nd of May, and in the morning on the 3rd June. The weather in July was hot (90°.1 at 11p. on the 14th) and close and there was very little wind. This was due to distant typhoons. On the 22nd and 23rd water-spouts were seen to the south of Hongkong. On the 20th at 7a., a double solar halo was observed by Mr. MAHOMET ALARAKIA. The radius of the inner was 23° and that of the outer about 45°. The barometric tide was great during dry weather. The beginning and also the end of August were very hot. Rain was frequent during the night and early morning. The first half of October was rather close, warm and damp. The latter part of the month was dry and clear as usual. The force of the wind during November fell far short of the average and the weather was warm in consequence. This continued in December, during which month the amount of cloud and rain was excessive.
27. At the Observatory the cisterns of the barograph and standard barometer are placed 109 feet above mean sea level. The bulbs of the rotating thermometers are swung 108 feet above mean sea level and 4 feet above the ground. The solar radiation thermometer is placed at the same height but the terrestrial radiation thermometer is only about one inch above the grass. The rim of the pluviograph is placed 105 feet above mean sea level and 21 inches above the ground. The cups of the anemograph are 149 feet above mean sea level and 45 feet above the ground. At Victoria Peak the instruments, except the radiation thermometers and the rain-gauge are placed in the look-out. The cistern of the barometer is 1814 feet above mean sea level. The bulbs of the thermometers are about 4 feet above the floor except the maximum thermometer, which is a few inches higher. The radiation thermometers are placed at the same height above the ground as at the Observatory. The rim of the rain-gauge is 8 inches in diameter and one foot above the ground.
28. The Monthly Weather Reports are arranged as follows:-
:-
Table I exhibits the hourly readings of the barometer reduced to freezing point of water but not to sea level, as measured (at two minutes to the hour named) from the barograms.
Tables II and III exhibit the hourly readings of the temperature of the air and of the temperature of evaporation round the Observatory as determined by aid of rotating dry and damp bulb thermometers and the thermograms. Table II exhibits also the extreme temperatures during the day and Table III also the solar radiation (black bulb in vacuo) maximum and terrestrial radiation-minimum tempera-
tures.
Table IV exhibits the mean relative humidity in percentage of saturation and mean tension of water vapour present in the air expressed in inches of mercury for every hour in the day and for every day in the month, calculated by aid of Blanford's tables from the data in Tables II and III.