F 8
No progress has been made with the construction of Pilot Charts owing to the absence on leave of the Chief Assistant.
Comparison of Barometers.-During the year about 1,300 comparisons of ships' barometers have been made by means of observations taken when in harbour, and several direct comparisons of barometers for shipmasters and various persons in the Colony have been made at the Observatory.
VII. MAGNETIC OBSERVATIONS.
Absolute determinations of magnetic horizontal force and declination were made near the middle of each month with a Kew pattern magnetometer, Elliott No. 55, and of dip with a Kew pattern dip circle, Dover No. 71, four dip needles being used in rotation. A complete determination of horizontal force consists of one set of vibrations taken between two sets of deflections.
Kew Magnetometer, Elliott No. 83, which was sent to England to be altered in 1914, was received back in February. It has been much improved.
From 7 comparisons made at the Kew Observatory in February, June, and July, 1915, it appeared that, with vibration magnet 83 and mirror magnet 83c, Elliott No. 83 gave smaller values of X than the Kew Standard by 22γ. (In the Annual Report for 1915 the difference is given as 30γ, but Dr. Chree informs me that the standard values of X originally furnished should be reduced by 8γ, on account of the difference between the provisional values of K, P, and Q, and those finally adopted for the year 1915.)
From four comparisons made in December 1916, it appeared that Elliott No. 55 gives smaller values of X than Elliott No. 83 (with vibration magnet 83) by 22γ, indicating that Elliott No. 55 gives results 44γ smaller than the Kew Standard. No correction has been made in this or any previous Report, however, to the results obtained from Elliott No. 55.
From a report on the results of comparisons of the Hongkong Magnetic instruments with those of the Carnegie Institute, Washington, made at this Observatory in the spring of 1915, it appears that the published values of X by Elliott No. 55 are lower than the International Magnetic Standard by 42·4γ, indicating that the I.M.S. agrees very closely with the Kew Standard.
As regards declination, Elliott No. 55 gave values 0'·4 lower than the I.M.S., and as regards dip, Dover No. 71 gave values 1'·8 greater than the I.M.S.
VIII.-TIME SERVICE.
Time Ball.-The Time Ball on Blackhead's Hill is dropped daily at 13h, Hongkong Standard Time (5 a.m. of Greenwich Time). The ball is also dropped at any other hour in case of necessity. One application for a supplementary time signal was made in the year 1916.
F 8
No progress has been made with the construction of Pilot Charts owing to the absence on leave of the Chief Assistant.
Comparison of Barometers.-During the year about 1,300 com- parisons of ships' barometers have been made by means of obser- vations taken when in harbour, and several direct comparisons of barometers for shipmasters and various persons in the Colony have been made at the Observatory.
VII. MAGNETIC OBSERVATIONS.
Absolute determinations of magnetic horizontal force and declin- ation were made near the middle of each month with a Kew pattern magnetometer, Elliott No. 55, and of dip with a Kew pattern dip circle, Dover No. 71, four dip needles being used in rotation. Ä complete determination of horizontal force consists of one set of vibrations taken between two sets of deflections.
Kew Magnetometer, Elliott No. 83, which was sent to England to be altered in 1914, was received back in February. It has been much improved.
From 7 comparisons made at the Kew Observatory in February, June, and July, 1915, it appeared that, with vibration magnet 83 and mirror magnet 83c, Elliott No. 83 gave smaller values of X than the Kew Standard by 22y. (In the Annual Report for 1915 the difference is given as 30y, but Dr. Chree informs me that the standard values of X originally furnished should be reduced by 87, on account of the difference between the provisional values of K, P, and Q, and those finally adopted for the year 1915.)
From four comparisons made in December 1916, it appeared that Elliott No. 55 gives smaller values of X than Elliott No. 83 (with vibration magnet 83) by 22y, indicating that Elliott No. 55 gives results 44y smaller than the Kew Standard. No correction has been made in this or any previous Report, however, to the results obtained from Elliott No. 55.
From a report on the results of comparisons of the Hongkong Magnetic instruments with those of the Carnegie Institute, Wash- ington, made at this Observatory in the spring of 1915, it appears that the published values of X by Elliott No. 55 are lower than the International Magnetic Standard by 42'4y, indicating that the I.M.S. agrees very closely with the Kew Standard.
As regards declination, Elliott No. 55 gave values 0'4 lower than the I.M.S., and as regards dip, Dover No. 71 gave values 1'8 greater than the IM.S.
VIII.-TIME SERVICE.
Time Ball.-The Time Ball on Blackhead's Hill is dropped daily at 13, Hongkong Standard Time (5 a.m. of Greenwich Time). The ball is also dropped at any other hour in case of necessity. One application for a supplementary time signal was made in the year 1916.
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