162 
LIEUT.-COLONEL SABINE ON TERRESTRIAL MAGNETISM. 
computed values ; in this case the inclination and total intensity being both furnished 
at the several points by observation with Mr. Fox’s apparatus, we have the ratios of 
... . . . 4>' cos 6' 
the horizontal intensity ^ cos g 
on board as 
follows : — 
N. 
N.N.E. l 
N.N.W. J 
= 0-9262 ; 
> = 0-9308; 
E.N.E. 4 
W.N.W.J 
E. | 
= 0-9608 ; 
5.5. E. 4 
5.5. W. } = 1,0615 ; 
S.E. 3 
S.W. H' om; 
N.E. ] 
\ = 0-9340 ; 
W. J 
= 0-9838 ; 
N.W. J 
s. 
= 1-0800; 
E.S.E. 3 
w.s.w.j 1,0084 ; 
From which by the formula 
we have 
= A' 
(cos <^cos £ + b sin 
<f sin < 
At 
N. 
A' = 
At : 
N.N.E. and N.N.W. 
A' = 
At 
N.E. and N.W. 
A' = 
At E.N.E. and W.N.W. 
A' = 
At 
E. and W. 
A' = 
At 
E.S.E. and W.S.W. 
A' = 
At 
S.E. and S.W. 
A' = 
At 
S S.E. and S.S.W. 
A' = 
At 
S. 
A' = 
0-9262 
0-9239 
0-9308 
0-9270 
0-9340 
0-9374 
0-9608 
0-9555 
0-9838 
0 - 9917 
1 - 0084 
1-0122 
1-0432 
1-0433 
1-0615 
1-0673 
1-0800 
1-0761 
= 1*003 
= 1-004 
= 0-992 
= 0996 
= 1-004 
A' = 0-999 Mean. 
The correction for the ship’s attraction in the general table of the intensities ob- 
served in the Erebus, have been computed with this value of A' used in the formula 
A' c tan 6 -f- cos cos 6 cosec & ; 6 being taken from the chart formed from the 
observations of the inclination, and & and £Trom the tables with the arguments 6 and <^'. 
