224 C. F. GAUSS ON THE GENERAL THEORY OF 



The exact computation of the places of these two poles, ac- 

 cording to our elements, gives them as follows : 



1. In 73° 35' north lat., 264° 21' long, east from Greenwich, 

 the value of the total intensity being = 1*701 in the unity in 

 common use. 



2. In 72°35' south lat., 152°30' long., the total intensity = 2-253. 



At the first of these points -^ hasits greatest value, = + 895*86 ; 



at the second its smallest value, = — 1030*24. 



According to Captain James Ross's observation the north mag- 

 netic pole falls 3° 30' to the south of its position according to our 

 calculation, which gives at that place a direction of the magnetic 

 force, differing 1° 12' from observation, as may be seen in the 

 table of comparisons. We must expect a considerably greater 

 displacement of the position of the southern pole. At Hobart 

 Town, which is the nearest station to this pole, calculation gives 

 too low a dip by 3° 38', as far as the observation can be de- 

 pended upon. It seems probable, therefore, that the actual south 

 magnetic pole is considerably north of the position given by our 

 calculation, and that it may be looked for in about 66° lat., and 

 146° long. 



31. 



The two points on the earth's surface where the horizontal force 

 vanishes, and which are called magnetic poles, may, it is true, 

 be allowed a certain significancy on account of their relation to 

 the form of the phenomena of the horizontal force all over the 

 earth ; but we must be careful not to give them undue consider- 

 ation. The chord which unites these two points has no signi- 

 ficancy, and it would be a gross mistake to call it the magnetic 

 axis of the earth. The only mode of giving a generally valid 

 signification to the idea of the magnetic axis of a body is laid 

 down in the 5th Article of the Intensitas Vis Magnetica, where 

 it is understood to mean the straight line in which the moment 

 of the free magnetism contained in the body is a maximum. In 

 order to determine both the position of the magnetic axis of the 

 earth in this sense, and the moment of the earth's magnetism in 

 relation to this same axis, we only require, as noticed in Art. 17, 

 a knowledge of the members of the first order of V. According 

 to our elements. Art. 26, P' = + 925*782 cos u + 89*024 sin u 



