72 SEVENTH REPORT—1837. 
3. The two centres of magnetic attraction in the northern 
hemisphere are not at opposite points ; in other words, the dif- 
ference of geographical longitude between them is not 180°, 
measured both ways. 
This is also best evidenced by inspection. Their distances 
apart are more nearly 200° measured across Greenland and 
Norway; and 160° across Behring’s Strait. 
4. The magnetic intensity is unsymmetrically distributed in 
the meridians of the northern hemisphere. 
This is a consequence of the two centres being nearer to 
each other in the one direction than in the other. If we 
imagine the hemisphere to be divided into two equal sections, 
by a plane coinciding with the meridians of 100° and 280° (Plate 
V.), the American division, which we may call the western sec- 
tion, will contain both centres of attraction, and a higher mea- 
sure of intensity will be seen to be spread over its meridians 
than in the corresponding latitudes in the eastern section. 
Thus we find, that in 150 meridians, or in five-sixths of the 
eastern section, no intensity of so high a value as 17 has been 
found within the range of observation, and probably does not 
exist ; whilst in the western section there is not a single me- 
ridian in which a higher intensity than 1°7 is not found. Europe 
is situated nearly midway between the centres at their widest 
separation, and we find that throughout Europe (with possibly 
the exception of its S.W. extremity in Spain), the magnetic 
intensity is weaker in every latitude than in the same parallels 
elsewhere in any other part of the hemisphere. 
5. The lines of intensity in the southern hemisphere havea 
general analogy with those in the northern hemisphere. 
The materials from whence conclusions may be drawn are 
fewer in the southern than in the northern hemisphere; but 
aided by our acquaintance with the magnetic system and dis- 
tribution in the latter, we are enabled to trace the general 
analogy of the two hemispheres, though the particular con- 
clusions in the case of the southern must necessarily be less 
determinate and exact than those we have hitherto discussed. 
We have already seen that the lines of dip and force depart 
from parallelism with each other even more in this hemisphere 
than in the northern. We may also perceive in the portions 
of the curves, which observations have as yet enabled us to trace, 
evidence of the same double flexure which in the other hemi- 
sphere we have seen to be characteristic of two centres of 
governing influence, The radii vectores carried from the south 
