Addendum. 



Ixxi 



Table 17. Results of Observations for the Absolute Horizontal Intensity made 

 with Circle Magnetometers in 1846 and 1847. 



Date. 



Magnet- 

 ometer. 



Ma^ 



Sus- 



jnet 

 Deflect- 



m, 

 Log- 



P. 



Q- 



Log ra X. 



Result. 

 „ Bifilar 



X at the 

 Mean 

 Bifilar 







pended. 



ing. 













Reading. 



for 1845. 



1846. 























June 23 



6-in. Circle. 



1 



F 



9-1603750 



-1-0-016708 



-0-003344 



0-2146240 



3-3661 



568-7 



3-3528 



1847. 























Jan. 2 



6-in. Circle. 



2 



F 



9-1564802 



-0-005080 



-H 0-002391 



0-2107538 



3-3662 



560-9 



33564 



May 31 



9-in. Circle. 



3 



M 



9-1810278 



-1- 0000655 



-0000600 



0-2420858 



3-3926 



574-8 



3-3764 



June 15 



9-in. Circle. 



3 



M 



9-1731457 



4-0-000172 



-0-000526 



0-2.344397 



3-3935 



576-7 



3-3765 



Sept. 11 



9-in. Circle. 



4 



M 



91732756 



-1-0-000899 



-0-000729 



0-2310949 



3-3799 



545-0 



3-3774 



Sept. 13 



9-in. Circle. 



4 



B 



9-0952645 



-0-002388 



-1-0-000387 



0-1518040 



3-3750 



524-9 



3-3816 



The resulting values of X, by Professor Forbes' instrument, differ considerably 

 from those by Sir Thomas Brisbane's, while the latter agree much better with the 

 results obtained with the 15-inch bars, see Table 12. 



Makerstotjn, Mav(-h 1849. 



