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TEEEESTRIAL ISOMAGNETIC LINES FOR SOUTH AFRICA 
FOR THE EPOCH JULY 1, 1903. 
By J. C. Beattie, D.Sc, F.R.S.S.Af. 
(With Four Maps, Plates VIII., IX., X., XL) 
(Read June 21, 1911.) 
The terrestrial isomagnetics dealt with in this paper are those of 
vertical, total, northerly, and westerly intensity. The true isomagnetics 
for these intensities for the epoch July 1, 1903, have already been given 
in another place ; " the data given there have been used in preparing the 
maps for the terrestrial lines, and in so far as they are here required are 
quoted in the following table : — 
Table 1. 
Mean Station 
of District.! 
A. 
z. 
T. 
X. 
Y. 
I 
33°46'S. 
18°57'E. 
•30669 
•35681 
•16034 
•08727 
II 
33 52 
20 49 
•31266 
•36096 
•15861 
•08573 
Ill 
33 36 
23 0 
•31845 
•36530 
•15771 
•08347 
IV 
33 25 
25 1 
•32298 
•36848 
•15775 
•08132 
V 
31 39 
28 32 
•32758 
•37302 
•16117 
•07630 
VI 
29 43 
30 31 
•32838 
•37510 
•16611 
•07305 
VII 
27 42 
30 3 
•32008 
•37100 
•17313 
•07213 
VIII 
27 57 
27 49 
•31570 
•36736 
•17258 
•07515 
IX 
25 59 
30 14 
•31572 
•36999 
•17946 
•07065 
X 
26 35 
27 56 
•31252 
•36645 
•17618 
•07429 
XI 
29 38 
26 12 
•31587 
•36573 
•16698 
•07748 
XII 
31 38 
25 19 
•31927 
•36696 
•16217 
•08009 
XIII 
31 58 
21 31 
•30962 
•35973 
•16255 
•08409 
XIV 
30 26 
22 0 
•30608 
•35792 
•16620 
08310 
XV 
23 53 
29 44 
•30722 
•36615 
•18671 
•06947 
The above results were next treated by the method first used by 
Mathias.:|; The mean station of District XI. was taken as reference 
* " Report of a Magnetic Survey of South Africa," by J. C. Beattie, 1909, R.S.L.. , 
f Loc. cit., p. 52. 
J " Annales de I'Observatoire Astronomique, Magnetique et Meteorologique de 
Toulouse," T. 7. "Eecherches sur le Magnetisme terrestre par E. Mathias." Paris, 
1907. 
