to the Antarctic Regions. 181 



It is not to be supposed that Captain Ross, having already signal- 

 ized himself by attaining the northern magnetic pole, should require 

 any exhortation to induce him to use his endeavours to reach the 

 southern. On the contrary, it might better become us to suggest 

 for his consideration, that no scientific datum of this description, nor 

 any attempt to attain very high southern latitudes, can be deemed 

 important enough to be made a ground for exposing to extraordinary 

 risk the lives of brave and valuable men. The magnetic pole, though 

 not attained, will yet be pointed to by distinct and unequivocal indi- 

 cations ; viz. by the approximation of the dip to 90° ; and by the con- 

 vergence of the magnetic meridians on all sides towards it. If such 

 convergence be observed over any considerable region, the place of the 

 pole may thence be deduced, though its locality may be inaccessible. 



M. Gauss, from theoretical considerations, has recently assigned 

 a probalile position in Ion. 146° E., lat. 66° S., to the southern mag- 

 netic pole, denying the existence of two poles of the same name, in 

 either hemisphere, which, as he justly remarks, would entail the ne- 

 cessity of admitting also a third point, having some of the chief cha- 

 racters of such a pole intermediate between them. That this is so, 

 may be made obvious without following out his somewhat intricate 

 demonstration, by simply considering, that if a needle be transported 

 from one such pole to another of the same name, it will begin to de- 

 viate from perpendicularity towards the pole it has quitted, and will 

 end in attaining perpendicularity again, after pointing in the latter 

 part of its progress obliquely towards the pole to which it is moving, 

 a sequence of things impossible without an intermediate passage 

 through the perpendicular direction. 



It is not improbable that the point indicated by M. Gauss will 

 prove accessible ; at all events it cannot but be approachable suf- 

 ficiently near to test by the convergence of meridians the truth of 

 the indication ; and as his theory gives within very moderate limits 

 of error the true place of the northern pole, and otherwise represents 

 the magnetic elements in every explored region with considerable ap- 

 proximation, it is but reasonable to recommend this as a distinct point 

 to be decided in Captain Ross's voyages. Should the decision be 

 in the negative, i. e. should none of the indications characterizing 

 the near vicinity of the magnetic pole occur in that region, it will 

 be to be sought ; and a knowledge of its real locality will be one of 

 the distinct scientific results which may be confidently hoped from 

 this Expedition, and which can only be attained by circumnavigating 

 the antarctic pole compass in hand. 



The actual attainment of n. focus of maximum intensity is rendered 

 difficult by the want of some distinct character by which it can be 

 known, previous to trial, in which direction to proceed, when after 

 increasing to a certain point the intensity begins again to diminish. 

 The best rule to be given, would be (supposing circumstances would 

 permit it) on perceiving the intensity to have become nearly station- 

 ary in its amount, to turn short and pursue a course at right angles 

 to that just before followed, when a change could not fail to occur, 

 and indicate by its direction towards which side the focus in ques- 

 tion were situated. 



