84 L. H. Bigelow—The Earth a Magnetic Shell. 
be obtained by treating the variations of the daily means on 
the monthly mean. It is the principal object of this paper to 
show the result of the detailed computation carried out for 26 
stations, whose cause has been attributed to the polar magnetic 
field from the sun. | 
Fig. 2. 
Midnight 
12 
GAT 
Noovw, 
Deflecting forces of the Equatorial Electro-magnetic Field, North Magnetic 
Hemisphere. 
The elimination of the polar field from the permanent and 
the electro-magnetic fields consists in taking the variations of 
the daily means of the 24 hourly observations on the mean for 
the months. This gives the three rectangular codrdinates 4 H, 
4D, 4 V, of the impressed vector that disturbs the mean from 
day to day. These values, as they appear in the volumes, are 
transformed into C. G. 8S. units of the fifth decimal place dz, 
dy, dz; finally the equivalent polar coordinates are computed, 
