LIEUT.-COLONEL SABINE ON TERRESTRIAL MAGNETISM. 



29 



§ 4. New Determination of the Magnetic Elements at Otaheite. 



In M. Gauss's " General Theory of Terrestrial Magnetism*," there is a note to 

 the following effect : — " Otaheite is a station of the highest importance for the future 

 improvement of the magnetic elements: the difference between the two determina- 

 tions of intensity made there by different observers, viz. Erman M72 in 1830, and 

 FiTzRoY 1*017 in 1835, is much greater than can with any degree of probability be 

 attributed to yearly changes, and considerably exceeds the greatest difference between 

 the computed and observed intensities at the eighty-six stations at which tlie theory 

 has been compared with observations." 



The importance which M. Gauss attached to a more exact determination of the 

 magnetic elements at Otaheite was communicated to Captain Belcher in a letter 

 from Captain Beaufort, which also conveyed to him permission from the Admiralty 

 to touch at that Island on his homeward voyage. Quitting Bow Island in March 

 1840, Captain Belcher arrived at Otaheite in April, and made there the obser- 

 vations contained in Tables XI. and XIII., of which the results are given in Tables 

 XII. and XIV. 



Table XI. — Observations with the Intensity Needles at Otaheite. 



1840. 



April 4 

 April 4 

 April 4 

 May 

 May 

 May 

 May 

 May 

 May 

 May 

 May 

 April 171 

 April 17 

 May 6\ 

 May 6 1 

 May 6 1 



Needle. 



Time. 



s 

 483-9 

 483-7 



484-2 

 482-8 

 482-1 

 480-8 

 482-3 

 482-2 

 482-2 

 481-6 

 481-3 

 480-1 

 480-6 

 547-9 

 647-9 

 548-4 



Therm. 



87" 



87 



88 



90 



90 



74 



86 



88 



89 



76 



73 



771 



77/ 



94l 



94 y 



77j 



Corrected 

 Time. 



479-5 



478-2 1 

 544-2 



1840. i Needle. Time. 



May 6 

 May 6 

 May 7 

 May 7 

 May 6 

 May 6 

 May 7 

 May 6 

 May 6 

 May 6 

 May 6 

 May 6 

 May 6 

 May 6 

 May 6 

 May 6 



8 



8 



8 



8 



9 



9 



9 



11 



11 



11 



12 



12 



12 



13 



13 



13 



478-9 

 479-1 

 479-6 

 478-6 

 443-3 

 443-4 

 444-2 

 480-6 

 480-4 

 480-7 

 408-8 

 409-1 

 409-2 

 399-8 

 400-7 

 400-6 



Therm. 



88" 



86 



77 



76 



85" 



84 



75 



72' 



80 



89 



72' 



85 



88 



73" 



86 



86 



Corrected 

 Time. 



476-3 



441-6 



478-0 



406-8 



398-2 



* Resultate fiir 1838, I. 



t Observed at Papeite : the other observations with No. 5, as well as all the observations with other needles, 

 were made at Point Venus. 



