NO. 7.] GENERAL RESULTS. 189 
ARRANGEMENT OF THE RESULTS IN GROUPS. 
As a determination of all three elements was made at only three stations, 
namely, Nos. 2, 152, and 179, it becomes necessary, if the total magnetic 
force, or its three orthogonal components, X, Y, Z, are to be calculated, to 
gather the stations into groups, and calculate the mean of the observation- 
results belonging to each group. This mode of procedure may be considered 
quite justifiable when we remember that the position of the Fram often 
changed only very slightly during long periods, and that the drift of the ice 
often carried the vessel back again to points in the neighbourhood of which 
observations had already been taken. By a calculation such as this of the 
mean values, we also obtain the advantage of being able to reduce to some 
extent the influence upon the results, of the magnetic disturbances that may 
be present. The area for each separate group, however, must of course 
not be made too large, as there would then be a risk of the variation of the 
magnetic elements with latitude and longitude not standing out with sufficient 
distinctness. As an experiment, I have taken as the greatest extent for a 
group, half a degree in latitude, and a number of degrees of longitude to 
correspond, which makes an area of about 3100 sq. kilometres. The number of 
degrees of longitude corresponding to a change of half a degree of latitude is 
2°4° in 78° of latitude 
96 = 19° 
28,30 — 
epee Pt meme 
3605.89) = 
Asien Gat g 
Lg) oS Wa 
Boj) ay Sone 
i es 
From the observation-results falling within each of the groups thus 
defined, I have calculated a mean declination, horizontal intensity, and ineli- 
nation, with corresponding mean geographic codrdinates, and thence again 
a mean value for the total intensity, W, and its three components, X, Y, 
