XIV 



Inteoduction. 



Table 4. — Reading of the Long Scale for the Magnetic Axis of the Declination Magnet. 



Position of 



First Series. 



Second Series. 



Third Series. 





Mean of 



Reading 





Mean of 



Reading 





Alean of 



Reading 



Magnet. 



Scale 



each 



for 



Scale 



each 



for 



Scale 



each 



for 





Reading. 



alternate 



Magnetic 



Reading. 



alternate 



Magnetic 



Reading. 



alternate 



Magnetic 







two. 



Axis. 





two. 



Axis. 





two. 



Axis. 



Inverted 









256-5 













Direct 



240-3 







253-9 



257-4 



255-65 



257-7 







Inverted 



270-8 



239-4 



255-10 



258-3 



251-2 



254-75 



252-5 



257-4 



254-95 



Direct 



238-6 



271-7 



255-15 



248-6 



259-4 



254-00 



257-1 



252-8 



254-95 



Inverted 



272-6 



237-9 



255-25 



260-5 



251-4 



255-95 



253-1 



257-6 



255-35 



Direct 



237-1 



273-6 



255-35 



254-1 



256-4 



255-25 



258-1 







Inverted 



274-5 



237-6 



256-05 



252-3 



258-1 



255-20 









Direct 



238-0 







2620 













Mean reading for magnetic axis, first series, 255'38 



second series, 255-13 



third series, 255*08 



Mean of all the partial results, 255 •21. 



Correction for effect of Bifilar and Balance Magnets (Table 5) +0-3 Sc. div., 

 adopted zero for 1842, 255-5 Sc. div. 



12. Corrections to be applied to the observed positions of the Magnet to obtain 

 the true declination. 



13. Effect of the Balance and Bifilar Magnets on the Declination Magnet. 



Table 5. — Effects of the Bifilar and Balance Magnets on the Declination Magnet. 



N. end of Magnet. 



Declination 

 Reading. 



Eifect of Magnet. 



Bifilar. 



Balance. 



Bifilar. 



Balance. 



W. 

 W. 



E. 



E. 



W. 



w. 



E. 

 W. 



w. 



E. 

 E. 

 W. 



143-30 

 141-38 

 142-57 

 144-47 

 14307 

 141-28 



0-59 

 0-70 



0-96 

 0-95 

 0-89 



Mean effect of Bifilar magnet on Declination magnet N. pole W.= — 0*64 Sc. div. 



Balance N. pole E.= +094 Sc. div. 



Sum =+0-30 Sc. div. 



After July 30. 1841, the north poles of the Bifilar and Balance Magnets were 



