359 



'Tx — 1.70 2.96—11.45 1.81—8.33—1.61 27.71 — 5.76 1.60-4.36 

 ^u — 6.42 — 1.89|— 3.02; 18.58 —34.41 —29.77 46.67 29.88,-0.31-3.36 



</'" and h'^ are the coefficients of the function P'", which Gauss used 

 in his "Allgemeine Theorie des Erdmagnetismus"', where: 



V 



R 



n = 00 



= 2 P,. 



n = l 



P„ ■= 2 (ff COS m X -\- h sin m ?.) P 



m=\ 



X represents the geographical longitude, V the potential, P the radins 

 of the earth, tiie functions P,, differing from the spherical harmonics 

 only by a numerical factor. 



It is worth notice that most of the coefficients in .t^. are much 

 snialler than those in n:^, whereas the sign is not always the same. 



3. If we want to know what part of these differences may be 

 ascribed to the choice of the sets of observations, we have first to 

 find out how far these coefficients represent the results of observation. 



In order to avoid disturbing influences as much as possible, we 



