61 
On the Phenomena of Terrestrial Magnetism : being an Abs¬ 
tract of the Magnetismus der Erde of Professor Ch. Han- 
steen. By Captain Edward Sabine, R.A., F.R.S. 
M. Hansteen’s attention was first attracted to the subject of 
terrestrial magnetism by seeing in the year 1807, at the Cosmo- 
graphical Society of Upsala, a terrestrial globe, in the southern 
hemisphere of which was delineated an ellipse entitled “ Regio 
polaris magnetica”, having two foci, one near Van Diemen’s 
Land entitled “ Regio fortior”, the other near Terra del Fuego 
entitled u Regio debilior”. The “ Regio magnetica” was stated 
on the globe to have been deduced by Wilcke from the observa¬ 
tions of Cook and Furneaux. This magnetic system being at 
variance with the opinion which then generally prevailed, that 
the magnetic phenomena could be adequately represented by a 
single magnetic axis, M. Hansteen was induced to examine the 
observations referred to, and which he found fully to bear out 
the view which Wilcke had taken of them. 
M. Hansteen proceeded to examine the observations which 
at that date had been made in the northern hemisphere. Those 
in the neighbourhood of Hudson’s Bay sufficiently pointed out 
a u Regio fortior” in that vicinity, whilst those of the philoso¬ 
phers who visited the northern parts of the old continent in 1768 
and 1769 to observe the transit of Venus, and of Schubert who 
visited Siberia in 1805, as clearly indicated the presence of a 
second point of magnetic attraction in the northern hemisphere, 
either in Siberia or in the sea to the north of it. This indica¬ 
tion was further confirmed by the existence of a line of no va¬ 
riation in the vicinity of the White Sea; manifesting that the 
attraction of the needle to the westward by the point near Hud¬ 
son’s Bay must be counterbalanced by an attraction acting from 
the opposite quarter, drawing the needle in a contrary direction ; 
the two attractions combined producing the intermediate direc¬ 
tion of the needle, in a line coinciding with the geographical 
meridian. 
The points of strongest attraction in each hemisphere appearing 
in nearly opposite points on the globe, and the points of weaker 
attraction the same, M. Hansteen was led to connect them re¬ 
spectively together; and from circumstances relating to their 
motion, hereafter to be explained, he was induced to prefer an 
hypothesis of two magnetic axes, one stronger, and the other 
weaker, to Wilcke’s hypothesis of elliptical magnetic regions. 
