237
The times of vibration exhibited in the table are each derived from 12 observations of the time occupied by the magnet in making 100 vibrations, corrections having been applied for rate of chrono- meter and arc of vibration.
The observations of horizontal force are expressed in C.G.S. units (one centimeter, one gramme, one second), but the monthly synopsis exhibits X, the horizontal, as well as Y, the vertical, and total forces, which have been computed by aid of the observed dips, and their value are also given in English units (one foot, one grain, one second) and in Gauss's units (one millimeter, one milligram, one second).
25. The cisterns of the barograph and standard barometers are placed 109 feet above M.S.L. The bulbs of the thermometers are rotated 108 feet above M.S.L., 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 M.S.L., and 21 inches above the ground.
26. 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 baro- grams.
Tables II. and III. exhibit the temperature of the air and of evaporation as determined by aid of rotating thermometers. Table II. exhibits also the extreme temperatures reduced to rotating thermometer. Table III. exhibits also the solar radiation (black bulb in vacuo) maximum temperatures reduced to Kew arbitrary standard.
Table IV. exhibits the mean relative humidity in percentage of saturation and mean tension of water vapour present in the air in inches of mercury, for every hour of the day and for every day of the month, 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, from half an hour before to half an hour after the hour (true time) named.
Table VI. exhibits the amount of rain (or dew) in inches registered from half an hour before to half an hour after the hour named. It exhibits also the estimated duration of rain.
Table VII. exhibits the velocity of the wind in miles and its direction in points (1-32). The velocity is measured from half an hour before to half an hour after the hour named, but the direction is read off at the hour.
Table VIII. exhibits the amount (0-10), name (Howard's classification) 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.
Table IX. exhibits: for every hour in the day, the mean velocity of the wind reduced to 4 as well as 2 directions, according to strictly accurate formulæ, and also the mean direction of the wind.
Below this is printed a list of the phenomena observed.
27. The following annual Weather Report for 1893 is arranged as follows:-
Table VII. exhibits the mean values for the year (or hourly excess above this) obtained from the monthly reports. The total duration of rain was 908 hours. There fell at least 0.01 inch of rain on 153 days.
Table VIII. exhibits the number of hours during a portion of which at least 0.005 inch of rain (or dew) was registered.
Table IX. 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 half to the other, e.g., half of the days when the wind was NNE are counted as N, and the other half as NE.
Table X. 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 XI. shows the frequency of clouds of different classes,
Table XII. is arranged as last year.
Table XIII. exhibits the monthly and annual extremes. The extremes of humidity and vapour tension are only approximate as the hourly values were not calculated.
Table XIV. contains five-day means.
Tables XV., XVI., XVII. contain magnetic observations.
The Honourable G. T. M. OBRIEN, C.M.G.,
Colonial Secretary, &c., &c., &c.
W. DOBERCK,
Director.