i8o SIEGE OF THE SOUTH POLE 
data which Hansteen utilised in his great work on the 
Magnetism of the Earth, published in 1819. Like Halley, 
he endeavoured to find what possible arrangement of 
magnets, hypothletically supposed to exist within the 
Earth, and to shift their position from time to time, would 
account for the varying phenomena observed on the sur- 
face and enable them to be predicted to the advancement 
of science and the advantage of navigation. Barlow, 
in 1833, also compiled an elaborate chart of magnetic 
declination and followed in the quest of a possible ex- 
planation, trying to fix what number of “ magnetic 
poles ” existed on the Earth or wandered over its sur- 
face. To him the problem appeared so insoluble that 
neither four nor any number of poles were sufficient to 
account for the observations, but he thought that “ there 
is no determinate pole to which all needles point, but that 
each place has its own particular pole and polar revolu- 
tion governed probably by some one general but unknown 
cause.” 
Meanwhile, the British Association, in the pride of its 
youth, was appointing committees to report on the exist- 
ing state of knowledge with regard to all branches of 
science, and magnetism received a full share of attention. 
Edward Sabine, an enthusiastic physicist rapidly gaining 
promotion as an Artillery officer in virtue of his scien- 
tific discoveries, had already carried out magnetic and 
geodetic surveys in many distant parts of the world, 
from the Arctic regions to the poisonous swamps of 
West Africa. James Clark Ross, a no less enthusiastic 
naval officer and tried Arctic explorer, had had the proud 
experience of localising the North Magnetic Pole — using 
that name for the point at which the compass ceased to 
have any directive force, but where the freely suspended 
