to the determination of the Magnetic Inclination. 163 



Table IV. 



The most correct value of the tangent of the inclination is 

 obtained from each of the series B, C, I>, E by dividing its sum 

 by the mean of the sums of the two series A, F. For this pur- 

 pose the corrections already mentioned, instead of being made 

 on each observation, may be made on their sums ; viz. — 



1. Instead of adding +p^" to each observation, +e — r-— ^ — 



may be added to the sum of the sixteen observations. 



T T !i^ . 1 1 t)X 



2. Instead of deducting k^; from each observation, -^ •- — 



62/ rr oZ rr 



may be deducted from the sum of all the sixteen observations, 



where 



1_^16 1—^32 \—C' 



16-3^4-4- +3^2 " 



P = 



\-d 



l-( 



■d^ 



l-< 



(--^) 



By this means the calculation will be simplified, inasmuch as 

 the value of it is constant. If wc represent the suras of the 

 series A, B, C, D, E, F by the same letters, then after making 

 this collection, wr obtain 



A = 2873-05 

 F=2877-15 



B = 6881-27 

 = 6886-10 

 D = 6889-36 

 E = 6887-98 



In this manner the following four determinations of the in- 



