The declination of the magnetic meridian was ascertained with considerable precision by means of the transit azimuth instrument: the needle seldom showed the same variation, as it oscillated about ten minutes, but the mean position of the magnetic meridian was 52' 10" west of the true. A coral reef was selected for the place of these observations, in order to avoid the attraction arising from buildings, or from inequalities in the ground.
* * * * *
Variation observed on board by Walker's Azimuth Compass.
29th Sept. 1816, P.M. ship's head W. by S. variation by
1st azimuth 0º. 51'. 30" west.
2nd 0 . 53 . 30
3rd 1 . 17 . 30
Amplitude 1 . 15 . 00
30th A.M. 1st azimuth 0 . 55 . 30
2nd 0 . 34 . 15
3d Oct. A.M. ship's head E.N.E. 1st azimuth 0 . 37 . 00
2nd 0 . 48 . 00
—————-
Variation by mean of 7 azimuths and 1 amplitude 0 . 52 . 39 west.
TABLE OF OBSERVATIONS
MADE WITH
DR. WOLLASTON'S DIP SECTOR:
WITH AN ENGRAVING, AND A DESCRIPTION OF THE INSTRUMENT, AND DIRECTIONS FOR ITS USE.
[Illustration: Wollaston's Dip Sector]