94
Table VII 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... half of the days when the wind was NNE are counted as N, and the other half as NE.
Table VIII exhibits the number of days on which certain meteorological pheno- mena were registered, and also the total number of thunderstorms noted in the neighbourhood during the past year.
Table IX shows the frequency of clouds of different classes.
Table X is arranged as last year.
Table XI exhibits the monthly and annual extremes.
Table XII contains fine-day means.
16. The observations of magnetic declination and horizontal force published in Tables XIII and XIV were made with magnet No. 55 on Kew pattern unifilar magnetometer ELLIOT BROTHERS, No. 55. The dips were observed with dip-circle Dover No. 71. The height above mean sea level at which the magnets are suspended is 116 feet.
The methods adopted in making the observations and in determining and applying the corrections are explained in Appendix G. of Observations and Researches inade in 1885- "On the verification of unifilar magnetometer ELLIOT BROTHERS, No. 55." The value of K used was 3.44914 at 25° Cent. The value of P was 8.032. The mean value of the magne- tic moment of the vibrating needle was 571.53. From comparisons made between magne- tometers No. 55 and No. 83 in the year 1898 it was shown that the correction to the horizontal force obtained by the former as given in Tables XIV and XV was +0.00052 (see
Observations and Researches made in 1898," page 19.)
The times of vibration exhibited in Table XIV are each derived from 12 observations of the time occupied by the magnet in making 100 vibrations, corrections having been applied for rate of chronometer and are of vibration.
The observations of horizontal force given in Table XIV are expressed in C.G.S. units The vertical and total forces have been computed by aid of the observed dips.
During the past year gangs of coolies have been at work excavating the hill-side to the West of the magnetic but, and the erection of a church on the site thus formed has been in progress. The west side of the magnetic hut is now only 10 feet from the edge of the cut- ting which goes almost sheer down for over 30 feet.
Owing to the earth cutting in progress in close proximity to the observing hut, observa- tions could not be made in November.
At other times during the year they have been made under the following conditions :--
May 12th and 13th coolies cutting hillside with pick and shovel about 100 feet
North-west of observing pier and about 25 feet below its level.
*
May 15th the same work in progress about 30 feet West of observing hut. The
horizontal force observation was commenced but abandoned.
August 17th: during first quarter of observation coolies at work as above about
90 feet West of and about 25 feet below level of instrument.
December 11th, 12th, 13th, 14th, 15th and 18th; workmen engaged building out-
houses about 40 feet West of and about 30 feet below level of instruments.
17. An appendix about the occurrence of fogs along the coast of China illustrated by a diagram (Plate IV) is added, and also three plates (I, II and III) showing tracks of typhoons in 1905.
Hongkong, Observatory, 10th March, 1906.
W. DOBERCK,
Direc or.