NO. 6.] 



INTRODUCTION. VOYAGE ALONG THE COAST OF SIBERIA. 



LV 



The compass is, however, not a very trustworthy instrument in these 

 high latitudes. Owing to the feeble intensity of the horizontal component of 

 the earth's magnetism the local influence on board, as well as its variations, 

 attain relatively greater importance than in lower latitudes. Between the de- 

 parture from Vardo 1893 July 21 and the enclosure in the ice on September 

 22 Mr. SCOTT-HANSEN took in all 65 compass-bearings of the Sun or a star, 

 giving the sum of magnetic declination and local deviation, and 4 direct deter- 

 minations of the deviation by mutual settings between the compass on board 

 and another compass placed at a convenient distance ashore or on the ice. 

 In order to separate the declination and deviation it was necessary to examine 

 the declination first. Professor NEUMAYER'S isogonic chart for 1895 extends 

 to 75 of latitude, but by means of three determinations made by Mr. Scott- 

 Hansen during the voyage, and a good many taken during the following years 

 on the ice, it was possible to continue the curves and join the separated 

 branches on a polar map. 



An inspection of the values of the deviation thus found showed that it 

 could not be considered as constant for a given course during the whole 

 voyage. On putting the deviation in the usual form 



A + B sin a + C cos a + D sin 2a + E cos 2a 



where a is the compass-course from north through east, the constants were 

 determined separately for the following three periods, containing respectively 

 20, 22 and 26 observations (one of the 69 being omitted) taken between the 

 limits given in the table below. 



Limits of 



On solving the equations by the method of least squares the observations 

 of period II proved insufficient to determine the quadrantal deviation, most 

 of the observations having been taken in the first and the adjoining part of 



