134 AKSEL S. STEEN. TERRESTRIAL MAGNETISM. [NoRW. POL. EXP. 
we obtain 
a = 209° 33/ 
p= — 615! 
In order now to be able to calculate by formula (4) the 4 corresponding 
to any inclination-determination, it will clearly be necessary to know the 
total intensity. It is true that during the expedition, observations with the 
Fox apparatus for the calculation of the total intensity were also generally 
made simultaneously with the inclination determinations; but since the result 
of these — as will presently be more fully explained — can hardly be 
regarded otherwise than as a failure, the horizontal intensity may be intro- 
duced into formula (4) instead of the total intensity — the former having 
been determined by separate observations independent of the Fox appa- 
ratus —, and we may put 
w= H 
~~ cos (I‘ + 24)’ 
whereby we obtain 
oe cos (I’-+ a), 
an equation which may easily be solved with regard to 4, when that quantity 
is assumed to be sufficiently small to allow of putting cos 4 = 1, and 
sn 4=/sin 1’. The final formula for 4 then becomes 
p.cos (I’ + a) cos I’ 
= Fe mara (lok Ga 6) 
By the aid of this formula, I have calculated the following table, which 
gives 4 for needle B, in minutes, for every degree of J’ from 83° to 87°, 
and for every 5th unit in the 3rd decimal place of the horizontal intensity 
from H = 0:035 to H = 0:070. 
