4 Transactions of tJie South African Philosophical Society. 



From the al)Ove results the secular variation of declination is as 

 follows : — 



Period. Secular Variation. 



IGOo to 1839 7' -56 increase of westerly declination. 



1841 „ 1850 1-30 



1843 ,, 1866 2-30 



1866 ,, 1869 Very nearly constant. 



1870 ,, 1890 2-80 decrease of westerly declination. 



1890 ,, 1900 3-91 



§ 4. The observations for intensity are fewer. The first recorded 

 trustworthy observation was made in 1843. So far as is known to 

 us, the results of all observations made since that date are contained 

 in the following list. 



The results are given in c.g.s. units. 



Date. 



1843. 

 1844. 

 1845. 

 1846. 

 1847. 

 1848. 

 1850. 

 1852. 

 1853. 

 1854. 

 1855. 

 1856. 

 1857. 

 Sept. 1857. 



Nov. 1873. 



Jan. 1890. 



Jan. 1895. 



Aug. 1897. 

 Jan. 1901. 



Observer. 



Horizontal Total 

 Intensity. Intensity. 

 c.G,'.s. units, c.ft'.s. units. 



Authorities. 



E. A. Detachment.. -2089 



.. -2069 



.. -2082 



Smalley -2080 



-2077 



„ -2072 



,, -2066 



Maclear -2059 



,, -2056 



„ -2050 



„ -2048 



,, -2044 



„ -2041 



-2056 



•3498 

 •3470 

 •3495 



J 

 •35061 

 •3511 

 •3516 1 

 •3517 

 •3511 

 •3507 J 

 •3684 



Sabine, ' Magnetical and 

 Meteorological Observa- 

 tions at Cape of Good 

 Hope,' vol. i. 



.Magnetic Kecords, K. Obs. 

 Cape of Good Hope. 



Preston 



•1989 

 •1916 



•3551 



Finlay -1900 



Finlay ^18835 



Beattie & Morrison -1851 



Reise der Novara. 



Challenjier Eeport, Narra- 

 tive, vol. ii. 

 1KAO (U.S. Coast and Geodetic 

 ''^^^'^ 1 Survey, Bull. 23. 



oSp I Magnetic Records, R. Obs. 



Secular Variation. 



Horizontal Intensity, 

 c.g.s. units. 

 1843 to 1855 -00035 annual decrease. 

 1855 „ 1901 • 00043 „ 

 1890-1 ,, 1901 • 00059 „ 



Total Intensity. 

 c.g.s. units. 



•00016 annual increase. 

 •00009 „ 



9 



APPENDIX I. 



The following results of observations of declination were carried 

 out at the Magnetic Observatory, at one time established at the Royal 

 Observatory, Cape Town. The observations for 1850-51-52 were a 

 continuation of those recorded in * Sabine's Magnetical and Meteoro- 

 logical Observations, Cape of Good Hope,' vol. i. The declination 



