170 
LIEUT.-COLONEL SABINE ON TERRESTRIAL MAGNETISM. 
in the formula for the equivalent weights to the force of the deflector observed else- 
where, viz. 
w' = 5'84 I' sin?;'. 
From the values of w 1 thus obtained, the subjoined Table has been formed of w' for 
each 20' of v for deflector N and deflector S, in the manner described in No. III. of 
these Contributions*; and with these values of w' we have the intensities I' relative 
to the force C820 at Hobarton computed by means of the formula 
I' = * w cosec v = * 1 7 1 w cosec v . 
in ° 
Deflector S. 
Deflector N. 
: V 
w\ 
u/. 
o 
/ 
gr- 
O 
/ 
gr- 
50 
0 
8-15 
47 
20 
7-90 
49 
40 
8-23 
47 
00 
7-95 
49 
20 
8-30 
46 
40 
8-00 
49 
00 
8-37 
46 
20 
8-06 
48 
40 
8-44 
46 
00 
8-11 
48 
20 
8-51 
45 
40 
8-16 
48 
00 
8-56 
45 
20 
2-21 
47 
40 
8-61 
45 
00 
8-25 
47 
20 
8-65 
44 
40 
8-30 
47 
00 
8-70 
44 
20 
8-33 
46 
20 
8-65 
44 
00 
8-37 
The results with the original magnets of the apparatus used conjointly, and desig- 
nated as “N and S,” are much inferior in precision to those obtained with the spare 
intensity needle used as a deflector. The angles of deflection were much less, owing 
to the force of the magnets, even when used conjointly, being very much inferior to 
that of the spare needle. The observations are of course given in the Table with the 
others, but as their results present on the one hand no systematic difference from 
those with the stronger deflector, and on the other hand are of inferior value, by 
reason of the extent of their fluctuation, — and as they could only tend therefore to 
impair the individual accuracy of the results with the stronger deflector and with the 
weights, — they have been omitted in the means. 
Comparison of the Intensities deduced by the Weights and by the Deflectors at the 
Stations at which both were employed. 
Station. 
Latitude. 
Longitude. 
Deflector S. 
Deflector N. 
Weights. 
Auckland Island. . 
— 50 33 
166 19 
1-862 
1-873 
1-852 
Campbell Island . . 
— 52 41 
169 10 
1-875 
1-898 
1-927 
On ice 
— 68 28 
176 32 
2-021 
2-044 
2-017 
At sea . 
-77 17 
187 18 
2-034 
2-038 
2-053 
At sea 
-77 39 
187 06 
2*041 
2-047 
2-053 
At sea 
— 63 00 
139 28 
2-043 
2-039 
2-041 
At sea 
— 58 13 
135 18 
2-042 
2-017 
2-037 
At sea 
-43 41 
146 03 
1-820 
1-884 
1-885 
* Philosophical Transactions for 1842, Art. II. 
