F 10
Comparison of Barometers.-During the year 170 comparisons of ships' barometer have been made by means of observations taken when in harbour. Several direct comparisons of barometers for shipmasters and various persons in the Colony have been made at the Observatory.
VII. MAGNETIC OBSERVATIONS,
The mean values of the magnetic elements for the years 1919 and 1920 were as follows:-
1919.
Declination (west) 0 19 50
Dip (north) 30 47 30
Horizontal Force (C. G. S. unit) 0·37191
Vertical Force (C. G. S. unit) 0·22146
Total Force (C. G. S. unit) 0·43270
1920.
0 20 45
30 40 22
0·37171
0·22151
0·43286
The series of magnetic observations made in the old magnetic hut since 1884 terminated in December, the site having been taken over by Government for European Assistants' Quarters. Observations in the new hut cannot be made until the building operations are finished.
Comparisons between Magnetometers Elliott 55 and 83 and Dip Circle Dover 71, in the old and new huts, were made between 1919 August and 1920 June, as opportunity offered.
The mean results of the observations are given below:--
(a) (b) (a)—(b) Number of observations Horizontal Force. Elliott 55 and vibration magnet 55 in old hut. 0.37162 Elliott 83 and vibration magnet 83 in new hut. 0·37216 0.00054 18 Elliott 55 and vibration magnet 55s. in old hut, 0.37201 in new hut. 0·37200 + 0·00001 57 Comparisons made in the year 1916 in the old hut gave:
Elliott 55 and vibration magnet 55A. = +22 y
Elliott 83 and vibration magnet 83.
It should be mentioned that prior to the comparisons in 1919-1920 the lens and scale of magnet 83 were transposed, for convenience of observing. The lens was originally at the north end of the magnet.