370 Mr. Christie on the diurnal deviations oj the 
From this it appears, that, as the magnets approached the 
centre of the needle, or as the intensity of their action increased , 
the westerly point of equilibrium proceeded towards the west , 
and the easterly towards the east ; that is, both receded from 
the north ; or the direction of the deviation of the first was 
plus and of the second minus. The southerly point of equi- 
librium, as the intensity increased, proceeded towards the 
south ; so that when the northern extremity of the axis of 
the magnets made an angle with the meridian towards the 
east, or in the direction minus, the southerly point of equilibrium 
deviated in the direction plus ; and when the angle was in 
the direction plus, the deviation of the southerly point, arising 
from the increased action of the magnets, was in the direction 
minus : that is, as the intensity of the action of the magnets 
increased, the southerly point of equilibrium deviated in a di- 
rection contrary to that of the angle which the axis of the 
magnets made with the meridian. 
Applying this to the variation of the terrestrial magnetic 
intensity, supposing that of the magnets constant, as this 
intensity decreased , the easterly and westerly points of equili- 
brium would both recede from the north, and the southerly 
would proceed towards the south ; as it increased, the easterly 
and westerly points would approach the north, and the southerly 
point recede from the south. Hence the deviation of the 
westerly point of equilibrium being minus, and, at the same 
time, that of the easterly point plus, would indicate an increase 
in the intensity of the terrestrial force ; and the same would 
be indicated by the receding of the southerly point from the 
south. If at the same time that the intensity of the terrestrial 
force increased, the direction of that urging the north end of 
