26 



PRESIDENTIAL ADDRESS. — SECTION A. 



were occupied in different parts of Africa, chiefly in the Cape 

 Colony. German South-West Africa, North-Western and 

 North-Eastern Rhodesia, British Central Africa, Portuguese 

 East Africa, German East Africa, British East Africa, and 

 Uganda. 



It is evident that the knowledge of the magnetic state of our 

 part of Africa has been considerably increased since 1890, a 

 remark which also applies to North Africa, particularly to 

 Egypt. We must not, however, rest yet. A glance at the 

 •accompanying map, which shows by a network of lines the 

 regions magnetically studied, lets us see that even in South 

 Africa there are still great tracts whose magnetic state is a 

 matter of conjecture. I need only mention the Kalahari, the 

 sjreater part of the Rhodesias, the western part of the continent 

 from Windhuk up to the Congo mouth, the greater part of 

 Portuguese East Africa, German East Africa, and British East 

 Africa. Magneticians must also keep in view the establishment 

 of one or more permanent stations; indeed, at the present day 

 probably that is more essential for the thorough magnetic study 

 of South Africa than anvthing else. 



APPENDIX. 



Terrestrial lines for declination, dip, and horizontal intensity 

 for South Africa. 



The data used for calculating these lines are taken from the 

 Report of a magnetic survey of South Africa alreadv referred 

 to. The stations in the Cape Province, Orange Free State, 

 Natal, and Transvaal were divided into 15 districts and a mean 

 station obtained for each district in the manner there described. 

 Station No. XI. was taken as the reference station, and a table, 

 No. 3, formed, in which are given the differences in latitude 

 (A0), longitude (A\), declination (AD), dip (Ad), and horizontal 

 intensity (All) of the different mean stations from the reference 

 station. 



Table No. 3. 



