(671) 
TErE ISOaONICS AND ISOCLINALS FOE SOUTH AFEICA FOE 
THE EPOCH JULY 1, 1913. 
By J. C. Beattie, D.Sc, Professor of Physics, South African College, 
Cape Town. 
(Eead October 20, 1915.) 
A first series of magnetic maps for South Africa was published in 1909, 
and consisted of seven maps, showing the true lines for declination, dip, 
horizontal intensity, total intensity, vertical intensity, northerly intensity, 
and westerly intensity. These maps embodied the results at approximately 
400 stations. 
A second series of maps was published in 1914. f These dealt with the 
magnetic elements in the western parts only of South Africa, and embodied 
the earlier and a number of additional results in this region. Three maps 
were given, showing the declination, dip, and horizontal intensity respectively 
for the epoch July 1, 1908. 
The two maps dealt with in this paper embody the results for declination 
and dip for all stations at which observations have so far been taken in 
South Africa — 667 in all. The observations have been taken chiefly in 1903 
and in 1909, and the results for these years and for other periods have been 
published from time to time.ij: In addition, the results obtained by Father 
E. G-oetz, S.J., and Mr, Wood in Ehodesia in 1914 have been supplied to me. 
A full report of their work will be published by them later. 
The reduction to the epoch was effected by the application of results 
obtained at repeat stations § — about forty in all. The distribution of these 
stations was satisfactory, except in Damaraland || and Ehodesia. In the latter 
* " Eeport of Magnetic Survey of South Africa/"' by J. C. Beattie, 1909. 
t " True Isogonics, Isoclinals, and Lines of Horizontal Intensity for the North- 
Western Parts of the Union of South Africa/' etc. Transactions Royal Society of 
South Africa, 1914, vol. iv, part 1, p. 57. 
X " Secular Variation of the Magnetic Elements in South Africa during the Period 
1900-1918." Transactions of the Eoyal Society of South Africa, 1915, vol. iv, 
part 3, p. 182. 
§ "The Secular Variation of the Magnetic Elements in South Africa," by J. C. 
Beattie. Transactions of the Royal Society of South Africa, 1915, vol. iv, p. 181. 
II In previous publications this country is referred to as German South-West 
Africa. 
