414 Mr. Christie on the magnetism of 
will however account for any disagreements that may be 
noticed in the absolute deviations in corresponding positions, 
as the greatest accuracy of adjustment would be requisite for 
their perfect agreement, when the opiate is so near to the 
poles of the needle. 
Having ascertained, by the observations when the plate 
was to the west of the needle, that the rapid rotation pro- 
duced no permanent change in the iron beyond that arising 
from the slow rotation, the deviations when any particular 
points of the plate were opposite to the needle being, as near 
as could be expected, the same after the rapid rotation as they 
were after the slow rotation in the first instance, the errors 
being sometimes in excess, sometimes in defect, as will 
appear by inspection of the first table, I did not repeat the 
observations on the effects of the slow rotation after the 
rapid, when the plate was to the east of the needle. 
The following tables contain the observations. The first 
four columns of deviations, are those which were observed 
when the plate was stationary, after having very slowly 
revolved, and also those when the needle pointed steadily 
during the rapid rotations. The deviations in the 5th and 
6th columns are obtained by taking half the difference be- 
tween those in the 1st and 2nd, and between those in the 
3rd and 4th columns, as the deviation due to the rotation 
when the plate's upper edge revolved from north to south. 
