1 82 SIEGE OF THE SOUTH POLE 
Not until 1837 had it been possible to present in a com- 
parable and trustworthy form the data of all three mag- 
netic elements — the declination or degree of variation of 
the needle from the true north, the dip or inclination of 
the needle to the horizon, and the total intensity of the 
magnetic force. The time was opportune, and the man 
was ready whose genius and training enabled him to com- 
bine these three elements, each elaborated by a brilliant 
specialist from the isolated labour of hundreds of observ- 
ers, into one stately and harmonious theory. It would be 
hopeless to attempt to describe the theoretical reasoning 
of Gauss in a popular book, and in this volume the theory 
of terrestrial magnetism concerns us only in so far as it 
was an incentive to Antarctic exploration. It must there- 
fore suffice to say that Gauss deduced a formula by which 
he could calculate the magnetic elements for any spot on 
the Earth’s surface at any time, and so far as observations 
were available by which this formula could be checked, it 
stood the test triumphantly. Amongst other conse- 
quences of the theory it was shown that a south magnetic 
pole similar to the north magnetic pole found by James 
Clark Ross in Boothia Felix must exist in or near the 
latitude of 66° S. and the longitude 146° E. It would 
naturally be a triumph for the theory if the south mag- 
netic pole were discovered in the region assigned, for 
the stations where magnetic observations were available 
in the southern hemisphere were so few that there, if 
anywhere, an error in calculation would be most likely 
to arise. 
The importance of obtaining observations to fill up 
the gaps in the magnetic maps had often been urged, but 
during the years from 1833 to 1837 the matter was 
receiving more and more earnest attention. The scien- 
