repetition of Mr. Chriseie’s experiments , &c. 
W 7 
II. 
Table of the mean deviations due to the rotation of the plate, 
its plane being in the secondary to the equator and meri- 
dian, and its centre at the distance of 16,5 inches from the 
centre of the needle. 
Position of the 
plate’s centre. 
)r mean read- 
if north end of 
e before rota- 
Mean of readings of 
north end of needle 
after plate had re- 
volved, its upper 
edge from 
Mean deviation of 
north end of needle 
due to rotation of 
plate, its upper edge 
from 
0) • 
3 Cl* 
-O O # 
r; _ G 
J .5 .2 
. 2 G £ 
> 0 .5 
o) -a 
-a <s £ 
2i 
3 ‘S 
Si 
Remarks. 
« to "O ’ 
East to 
West. 
West to 
East 
East to 
West. 
West to 
East. 
c 
B-§ 
Lat. 
Long. 
Zero 
ing 
nee 
tior 
Js! 
• O 
0 
0 
O / 
O 35W 
0 ' 
10 26 E 
O / 
4 42W 
1 1 i E 
0 ' 
4 7 W 
O ' 
+ 15 8 
+ i°6£ 
i turn in i min. 
O 
180 
i 24 E 
7 39 E 
5 40W 
68 57 W 
6 15 E 
7 4 W 
+ 13 19 
+ 133 
3 turns, slow. 
S 2 i S 
0 
69 6W 
68 5 1 W 
0 15 E 
0 9 E 
+ 06 
+ 12 
1 turn in i min. 
S 
1 80 
69 7 E 
69 12 E 
69 12 F 
0 5 E 
0 5 E 
0 0 
+ 12 
1 turn in i min. 
S 2 iN 
0 
7 l 4 E 
70 59 E 
70 47 E 
0 5W 
0 17W 
4- 0 12 
+ 18 
2 turns in 2 min. 
S 2 iN 
180 
71 i,W 
71 6W 
71 8W 
0 9 E 
0 7 E 
+ 02 
+ 18 
1 turn in 1 min. 
90 S 
1 00 E 
0 55W 
4 37 E 
i 55W 
3 37 E 
- 5 3 2 
+ 17 
3 turns, slow. 
90 N 
0 22 E 
3 19W 
4 6 E 
3 41 W 
3 44 E 
- 7 25 
+ 12 
1 turn in 1 min. 
It appears from these observations, that in latitude 52°-| 
North or South, the deviation due to rotation nearly vanished ; 
but I do not profess to have got the latitude of this point 
to any great degree of accuracy, the nature of the construc- 
tion of the instrument used, not admitting of the measure •- 
ments from the centre of the plate, to that of the needle, 
being taken sufficiently near for that purpose ; but I think 
it is obtained within the limits of a degree. 
