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IV. 
TERRESTRIAL MAGNETISM. 
MAGNETICAL INSTRUCTIONS FOR THE ANTARCTIC 
EXPEDITION, 1901. 
By Caprain E. W. Creak, F.RS. R.N. 
REGARDING the observation of the elements of Terrestrial Macnetism 
as one of the principal objects of the present Antarctic Expedition, 
every effort should be made to secure as complete a magnetic survey of 
the region south of the parallel of 40° S. as circumstances will permit. 
Enough is known of the magnetic elements in that recion to show 
that, except where observations have been made on land, as in South 
America and Tasmania, large changes in the Magnetic Declination or 
Variation have been going on since the time of Ross’s magnetic 
survey of 1839-43, the principal foci of such change being far out at 
sea, whilst the dip and intensity of the changes, of which there is 
scant information, are probably also subject to great alterations in 
their distribution. 
It should be borne in mind that Kew Observatory is the primary 
base station of the whole series of magnetic observations, with which 
it is specially desirable to connect by absolute measurements of the 
magnetic elements, land stations at the Cape of Good Hope and 
Meibourne, Lyttleton (New Zealand) and an Antarctic station in 
Victoria Land. 
The constants for the various instruments enumerated below have 
been determined at Kew, and it is necessary that immediately on the 
return of the Expedition to England, a re-determination of the con- 
stants should be made there. 
The principal base station of the survey in southern latitudes 
will be at Melbourne, where there is a fully equipped magnetic 
observatory. 
It is of great importance that a secondary base station should be 
established in Victoria Land, where, besides the other instruments, 
the differential instruments or Variometers can be successfully 
established. 
G2 
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