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It is proposed to make some experiments with a portable anemometer, which can be shifted readily to various positions on the roof, with a view to elucidating the cause of the change of factor with wind direction.
As regards velocity the results obtained in 1911 indicate that the factor remains practically constant with wind velocities above 10 miles per hour (Robinson).
Squall velocities and their relation to mean velocities as derived from the records of the pressure-tube anemograph during the typhoons of July 3rd to 4th, July 27th, and August 2nd to 7th are shown in Table XIV.
The daily maximum velocity of the wind in a gust, as recorded by the pressure-tube anemograph, is given in Table XI.
16. In February electric lamps for lighting the transit instrument were installed, the necessary current being supplied by means of accumulators.
The number of transits observed during 1911 was 1,195. The axis of the instrument was levelled 439 times, and the azimuth and collimation errors were determined 22 times by the aid of the meridian mark. With a few exceptions, these observations were made by Mr. Jeffries. The time-ball clock was cleaned and the sidereal standard clock oiled on November 9th. The going of all the standard clocks has been satisfactory.
17. The errors of the time-ball are given in Table I. The ball is not dropped on Sundays nor on Government holidays. There was one failure, on December 2nd, when the locking apparatus slipped owing to lack of tension on one of the springs, when the ball fell two minutes before one o'clock while the winding apparatus was still in gear. The pinion was broken. A new one was supplied by the Hongkong and Whampoa Dock Co. and fitted on December 5th. On July 3rd, 4th and 27th and on August 4th and 5th the ball was not hoisted owing to gales caused by typhoons in the vicinity of the Colony. It was dropped successfully 291 times in 1911. The probable error in January was 0s.18, in February ± 0s.11, in March ± 0s.14, in April ± 0s.15, in May ± 0s.23, in June ± 0s.14, in July ± 0s.15, in August ± 0s.13, in September ± 0s.15, in October ± 0s.16, in November ± 0s.15 and in December ± 0s.15.
In November the time-ball was overhauled by the Dock Co., some necessary repairs effected and the ball painted, without, however, interfering with its dropping at 1 p.m., which was continued as usual.
18. Dr. C. K. Edmunds who, from time to time during the past six years has been engaged in magnetic survey work in various parts of China, under the auspices of the Department of Research in Terrestrial Magnetism, Carnegie Institution, Washington, spent some days here in March and July in comparing his instruments with those of this Observatory.
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It is proposed to make some experiments with a portable anemometer, which can be shifted readily to various positions on the roof, with a view to elucidating the cause of the change of factor with wind direction.
As regards velocity the results obtained in 1911 indicate that the factor remains practically constant with wind velocities above 10 miles per hour (Robinson).
Squall velocities and their relation to mean velocities as derived from the records of the pressure-tube anemograph during the typhoons of July 3rd to 4th, July 27th, and August 2nd to 7th are shown in Table XIV.
The daily maximum velocity of the wind in a gust, as recorded by the pressure-tube anemograph, is given in Table XI.
16. In February electric lamps for lighting the transit instrument were installed, the necessary current being supplied by means of accumulators.
The number of transits observed during 1911 was 1,195. The axis of the instrument was levelled 439 times, and the azimuth and collimation errors were determined 22 times by the aid of the meridian mark. With a few exceptions, these observations were made by Mr. Jeffries. The time-ball clock was cleaned and the sidereal standard clock oiled on November 9th. The going of all the standard clocks has been satisfactory.
17. The errors of the time-ball are given in Table I. The ball is not dropped on Sundays nor on Government holidays. There was one failure, on December 2nd, when the locking apparatus slipped owing to lack of tension on one of the springs, when the ball fell two minutes before one o'clock while the winding apparatus was still in gear. The pinion was broken. A new one was supplied by the Hongkong and Whampoa Dock Co. and fitted on December 5th. On July 3rd, 4th and 27th and on August 4th and 5th the ball was not hoisted owing to gales caused by typhoons in the vicinity of the Colony. It was dropped successfully 291 times in 1911. The pro- bable error in January was Os.18, in February ± 0s.11, in March
0s.14, in April ± 08.15, in May ± 0.23, in June ± Os.14, in July 08.15, in August ± 0.13, in September± 0.15, in October 08,16, in November ± 0.15 and in December ± 0s.15.
In November the time-ball was overhauled by the Dock Co., some necessary repairs effected and the ball painted, without, how- ever, interfering with its dropping at 1 p.m., which was continued as usual.
18. Dr. C. K. Edmunds who, from time to time during the past six years has been engaged in magnetic survey work in various parts of China, under the auspices of the Department of Research in Terrestrial Magnetism, Carnegie Institution, Washington, spent some days here in March and July in comparing his instru- ments with those of this Observatory.
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