Magnetism of the Earth. 153 



their respective intensitieSj 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 v/ith v/hich 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 estabhsh 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 prose- 

 cution of such researches at sea, and presenting embarrassments, 

 which, to say the least of them, are very difficult to surmount, and 



Vol. XVII.— No. 1. 20 



