Sessional_Paper_1908 — Page 241

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19. 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 nor for gravity, as measured (at two minutes to the hour [mean time] named) from the barograms.

Tables II and III exhibit the temperature of the air and of evaporation as deter- mined by aid of rotating thermometers, Table II exhibits also the extreme temperatures reduced to rotating thermometers by comparisons of thermometers hung beside them. 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 Blan- FORD'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 (mean time) named. It exhibits also the observed duration of rain.

Table VII exhibits the velocity of the wind in miles, and its direction in points, 1 to 32,(8=E, 16=S, 24-W, 32-N). The direction is read off at the hour, but the velocity is measured from half-an-hour before to half-an-hour after the hour (mean time) named, the distance actually run by the cups being multiplied by 3 (Dr. ROBINSON's original factor). This factor is now known to be too large, but it is retained for the present to avoid confusion in the comparison with other records.

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. With regard to the names of clouds, nimbus (nim) is entered only when rain is seen to fall, when no rain is seen to fall cumulo-nimbus (cum-nim) is entered. This name indicates clouds intermediate between cum and nim. Cumulo- stratus (cum-str) is the well-known thunder cloud, while strato-cumulus (str- cum) signifies a cloud intermediate between stratus and cum. Sm-cum means alto-cumulus.

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 formula, and also the mean direction of the wind. Below this is printed a list of the phenomena observed.

20. The following Annual Weather Report for 1907 is arranged as follows:-

Table III exhibits the mean values for the year (or hourly excess above this) obtained from the monthly reports. The total duration of rain was 487 hours. There fell at least 0.01 inch of rain on 150 days.

Table IV exhibits the number of hours during a portion of which at least 0.005

inch of rain (or dew) was registered.

Table V 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.