389 
iron arising from its rotation. 
equatorial north edge towards the north, the inclination 
of the needle was diminishedhy the rotation ; that is, the south 
edge of its equator deviated towards the north pole, and the 
north edge of its equator towards the south pole ; or the edges 
of the equator, hy the rotation of the plate, deviated in directions 
contrary to those in zvhich the edges of the plate moved. The 
same conclusion evidently follows from the observations 
when the equatorial south edge of the plate revolved towards 
the polar north, the dip being here increased by the rotation 
of the plate. 
The next observations which I made, were of the inclina- 
tions of the dipping needle, when the plane of the plate was 
in the plane of the meridian or plane of vibration of the dip- 
ping needle. 
IX. Table of the inclinations of the dipping needle, when the centre of the plate 
was in longitude 90 °, latitude 0 °, and its plane in the plane of the meridian, or 
plane of vibration of the dipping needle ; the distance of the centre of the plate 
from that of the needle being 13.3 inches. Plate ISo. I. 
Points on the 
Plate coincid- 
ing with the 
Polar South. 
Polar South edge of the Plate to Equatorial North, 
or 
Equatorial South edge to Polar South. 
Polar South edge of the Plate to equatorial South, 
or 
Equatorial South edge to Polar North. 
First Set. 
Second Set. 
First Set. 
Second Set. 
S. end. 
N. end. 
S. «end. 
N. end. 
S. end. 
N. end. 
S. end. 
N. end. 
o 
6o 
120 
I So 
240 
300 
0 / 
70 25 
69 50 
69 50 
70 45 
70 55 
70 40 
0 / 
70 35 
70 os 
70 00 
70 55 
71 os 
70 so 
0 t 
70 45 
70 IS 
69 55 
70 35 
70 so 
70 30 
0 / 
70 30 
70 OS 
69 so 
70 2S 
70 40 
70 IS 
0 / 
69 40 
69 20 
68 ss 
69 3 S 
60 30 
69 35 
0 / 
69 35 
69 IS 
68 SS 
69 40 
69 35 
69 40 
^9 35 
69 30 
69 00 
69 35 
69 20 
69 30 
^9 U 
69 20 
68 4 S 
69 2S 
69 10 
69 20 
Mean dip 70° 26' ^ 
efzz'l 
Mean deviation due to rotation. 04' 
