Magnetism of the Earth. 153 
their respective intensities, relatively to each other, and to the points 
of maximum in the northern hemisphere, remain to be determined ; 
and must be acknowledged to be subjects of highly curious and im- 
portant enquiry. In the arrangement of magnetism, as exhibited to 
us on the great scale of our globe ; differing, as it is now known to do, 
so widely from those analogies with which it had been associated, 
and. indeed, I believe, from all analogy whatsoever with which we 
are acquainted, we cannot too soon inform ourselves accurately of 
the facts. 
In selecting the parts of the southern hemisphere, in which, enqui- 
ries of this nature can be most advantageously pursued, regard must 
be paid, in the first instance, to the distribution of land, on account 
of the convenience which its coasts and islands afford in determining 
and connecting the isodynamic curves. ‘The eastern and western 
coasts of New Holland, and the adjoining islands of New Zealand— 
the western coast of South America, from Lima to Cape Horn, and 
a continuation of the lands to the southward of Cape Horn—approach- 
ing the Antarctic Circle—the islands which might be successively 
visited in a course from the Cape of Good Hope to Desolation Island, 
and from thence to the Mauritius—present in this view, the directions 
of principal interest. Careful observation systematically made in 
them, combined with the observations already made, would advance 
our knowledge of the magnetic phenomena of the southern hemis- 
phere, to the same stage that it has attained in regard to those of the 
northern : it would establish the number of the governing points of 
intensity in the hemisphere : determine their respective geographical 
positions, and, in great measure at least, their relative intensities : as- 
certain the general arrangement of the curves: and finally, point 
out those localities of peculiar interest, which it might be expedient 
to visit for more particular enquiry. A single expedition might ac- 
complish all this, without extending the duration of the voyage to an 
undue length, or interfering with other important objects of scientific 
research: and we may assuredly affirm, that were this service, ‘the 
single purpose, and sole object accomplished, by a scientific expedition, 
it would of itself confer no ordinary distinction. ; 
In what has hitherto been said, observations made on land have 
alone been taken into account : the motion of a ship, and the quantity 
of iron necessarily employed in her equipment, impeding the —- 
cution of such researches at sea, and presenting embarrassments, 
which, to say the least of them, are very difficult to surmount, and 
Vor. XVIL—No. 1. 20 
