136 AKSEL S. STEEN. TERRESTRIAL MAGNETISM. [NoRW. POL. EXP. 
whence we obtain amor 
p= —A4T8’. 
With these values substituted in formula (5) I have calculated 7 for the 
4 cases in which the inclination has been determined with needle B’. The 
calculation gave the following result: 
1893. Aug. 8 | O-1118 | 78° 56° —35' 78° 21! 
1894. May 4 | 00408 | 86 16 —48 85 28 
May 23 | 0:0395 | 86 18 —50 85 28 
June 1 | 00398 | 86 17 —50 85 27 
The value of H for Aug. 8th, 1893, was determined directly by obser- 
vation. I have determined the horizontal intensity for the remaining 3 days 
by graphic interpolation. 
THE OBSERVATIONS. 
No advantage was taken during the expedition of the opportunity afforded 
by the Fox apparatus of also determining the inclination indirectly by the 
aid of deflectors. 
The following list contains in chronological order all the inclination obser- 
vations taken, with a statement of the assumed value of the horizontal 
intensity for the place of observation, found by graphic interpolation from 
direct determinations of this element made at neighbouring places. As pre- 
viously mentioned, no note was made of the time at the setting of the incli- 
nation-needle, and therefore no exact time can be given for the calculated 
mean value of the inclination. On a few occasions, however, a statement 
has been added in the observation-journal as to whether the inclination deter- 
mination was made in the morning or the afternoon, this being indicated in 
the list with a.m. and p.m. respectively. When no time of day is stated, 
the given latitude and longitude apply to about midday, while a. m. is con- 
sidered as about 10 a.m., and p.m. as about 4 p.m. The mean of the 
’ 
meridian readings is entered under the heading “Mer.” and the readings of 
the north and south ends of the needle are indicated with N. and S, 
respectively. 
