261
21. As stated in the "Instructions for making Meteorological Observations, &c." meteorological instruments forwarded by observers, who regularly send their registers to the Observatory, are verified here free of cost. During the past year several instruments were verified.
22. At the Observatory the cisterns of the barograph and standard barometer are placed 109 feet above mean sea level. The bulbs of the thermometers are rotated 108 feet above mean sea level and 4 feet above the grass. The solar radiation thermometer is placed at the same height. The rim of the rain-gauge is 105 feet above mean sea level and 21 inches above the ground. At Victoria Peak the instruments, except the radiation thermometer and the rain-gauge are placed in the look-out. The cistern of the barometer is 1,814 feet above sea level. The bulbs of the thermometers are 4 feet above the floor except the maximum thermometer, which is a few inches higher. The rim of the rain-gauge is one foot above the ground.
23. 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 temperatures of the air and of evaporation as determined from readings of thermometers exposed in the shelter described above. All readings are reduced to the rotating thermometer by comparisons made every three hours or oftener. The extremes are reduced by aid of comparisons made during the hottest and coldest part of the day. The solar radiation (black bulb in vacuo) maximum temperature is re luced to the Kew arbitrary standard.
Table IV. exhibits the mean relative humidity in percentage of saturation and mean tension of vapour expressed in inches of mercury calculated by aid of Blanford's tables from the data in Tables II. and III.
Table V. exhibits the duration of sunshine expressed in hours froin half an hour before to half an hour after the hour (true time) named.
Table VI. exhibits the amount of rain in inches registered from half an hour before to half an hour after the hour named. It exhibits also the duration of rain estimated at the Observatory. The rainfall at Victoria l'eak is measured at 10a and entered to preceding day, but it is evident that the observer does not attend to the gauge regularly.
Table VII. exhibits the velocity of the wind in miles and its direction in points (0-31). The velocity of the wind is measured from half an hour before to half an hour after the hour named. The direction is read off at the hour. The mean direction for every day has been calculated taking into account the velocity at each hour.
Table VIII. exhibits for every hour in the day the mean velocity of the wind reduced to 4 as well as to 2 directions, according to strictly accurate formulae, and also the mean direction of the wind.
Table IX. exhibits the readings of the barometer reduced to freezing point of water but not to sea level, and of the thermometers, and the estimated direction and force (0-12) of the wind at Victoria Peak.
Table X. exhibits the amount (0-10), name and direction whence coming of the clouds. Where the names of upper and lower clouds are given but only one direction, this refers to the lower clouds.
24. The Annual Weather Report for 1890 is arranged as follows:—
Table IV. exhibits the mean values for the year (as hourly excess above this) obtained from the means given in the monthly reports, the nean hourly intensity of rain is obtained from table VI. of the monthly reports in connection with table V. of this report. The total amount of rain was 70.935 inches at the Observatory and 89.54 inches at the Peak. The total duration registered at the Obser- vatory was 582 hours. There fell at least 0.91 inch of rain on 128 days at the Observatory.
Table V. exhibits the number of hours during a portion of which at least 0.005 inch of rain was registered.
Table VI. exhibits the number of days with wind from eight different points of the compass.. The figures are obtained from the mean daily directions in table VII. of the monthly reports. Days with wind from a point equidistant from two directions given are counted half to one of these and halfTM to the other e.g. half of the days when the wind was NNE are counted as N and the other half as NE.
The VII. exhibits the number of days on which certain meteorological phenomena were registered, and also the total number of thunderstorms noted in the neighbourhood during the past year.
Table VIII. show the frequency of clouds of the different classes. Table IX. is arranged as in previous years.
Tables X. and XI. exhibit the monthly and annual extremes. The extremes of humidity and vapour tension can be regarded as only approximate as the hourly values are not calculated.
Table XII. contains the five-day means.
25. The following phenomena were noted during the different months of 1890:-
Solar Corona: on the 28th.
January, 1890.
Lunar Corona: on the 1st, 2nd, 5th, 6th, 26th, 27th, 28th, 30th and 31st.
Haze on the 1st, 2nd, 8th, 14th, 16th and 17th.
Fog: on the 19th, 27th and 29th.