324 L. A. Bauer— Variation of Terrestrial Magnetism. 
In 1780 it was consequently west of St. Helena and Ascension 
Islands but east of Rio de Janeiro. In 1750 it was still west 
of the first two stations though now nearer them, as is apparent 
from the secular variation curves—the increasing southerly 
inclination still prevailing in 1750. In 1885 it appears to have 
been close to Rio de Janeiro, and we ought to expect about this 
date the maximum northerly or minimum southerly dip to 
occur. As a matter of fact, this turning point was reached in 
about 1882 (see curve).* The southerly dtp is at present 
increasing, i. e., the secondary north end attracting pole will be 
found at the present time west of Rio de Janeiro. 
Similar considerations will explain to us the change in mag- 
netic declination at these three tropical stations. 
Enough has been given to show how exceedingly helpful 
the secondary magnetic poles may be to us in the study of the 
phenomena of the distribution and of the secular variation of 
geomagnetism. 
By watching the progressive westward motion of the second- 
ary south end attracting pole, which was in 1885 in about 5° 
south latitude and 40° east longitude we may be able to predict 
the coming of the phase of minimum northerly inclination 
which is at the present time setting in in central Europe and 
marching westwardly. 
It may be of interest and of value to give the dates at which 
the branch of the secondary magnetic equator corresponding 
to the shorter difference in longitude of the secondary poles 
passed through various stations along the line of westward 
march. The figures were obtained with the aid of the relation 
AL=0 = Iava— 2 tan — or Loves = Lompa = 2 tae 
Date of 
Station. Latitude. Longitude. Passage of 
md au. Sec. Mag’c Kq. 
Berlin 5e-32 N: 13 23: H. 1820 
Rome 41 53 12:26 1830 
Basle AT 34 7 36 1839 
Geneva 46 12 6 09 1845 
Paris 48 50 220 E 1858 
London 51 30 0 07 W 1862 
Equator 0! 0 24 aa ae 1780 
33 Oe 0 7 K. 1829 
es af 2 EK. 1840 
ef 0 O 9 W 1885 
Capetown . 33 56 18 29 E 1844 
St. Helena Island 15 55 S. 5 44 W. 1890 
Ascension “ 7 56 14 23 W. 1905 (?) 
Riode Janeiro 22 55 43 10 W. ae 
* Deduced by me in Beitraege zur Kenntniss des Wesens der Sac. Var’n, p. 36, 
before the presence of secondary poles had been recognized. 
