70 GEELMUYDEN. ASTRONOMICAL OBSERVATIONS. [NORW. POL. EXP. 



D. Determination of Magnetic Declination by Compass. 



Observer: Lieutenant Scott-Hansen, when not otherwise stated. 



Besides the regular observations taken in the magnetic observatory, the declination was 

 frequently determined by the bearing of the Sun or a star, taken with a compass at a convenient 

 distance from the ship. As these observations could not be made the subject of the same dis- 

 cussion as the other magnetical observations, which are contained in another memoir, the 

 results are given here at once, together with the latitude employed for the calculation of the 

 azimuth, and the longitude from the meridian of Greenwich. 



The comparisons between the watch and chronometer Hohwii are added only in the few 

 cases when they are not to be found in List A or B. The correction of Hw to local mean time, 

 necessary for the calculation of azimuth, will be found in a subsequent section. 



The observations of 1893, August 20 and 28, and the three first observations of 1895, 

 February 20, were taken by means of a small compass by Olsen, divided into degrees on 

 the rim from both ends of the diopter, and both ways to 90. As more than one observation 

 was always taken, the quadrant may be inferred from the increasing or decreasing of the num- 

 bers given in the column "Compass", which are the means of the readings of both ends of the 

 needle. Tbe compass used 1893, September 21, was graduated anti-clockwise from (at the 

 wire end of the diopter) to 360; the degrees given in the column "Compass" correspond to the 

 north end of the needle, but the fraction of degree is the mean for the two ends. 



All the other observations were taken with Hechelmann's Azimuth Compass, divided into 

 degrees on the card. With its gimbals it was suspended in a wooden box (spiked with copper 

 nails) and mounted on the ice; after observation it was generally left there, covered with a 

 canvass cap, unless cracking of the ice or other circumstances made it necessary to remove it. 

 Every number in the column "Compass" is the mean of the readings both ways. The quadrant 

 there given corresponds to the wire end of the diopter. When the Sun was too high for direct 

 setting, the mirror was used, and then always in the two positions of the instrument, with the 

 Sun in front or behind, which is indicated by "Front" or "Back" added in the column "Object". 

 When nothing is added, the bearing was taken directly. 



