512 The Centre of Gravity of the Earth , [September 
south declination, and near the South Pole, is 0 Hydri, with 
a right ascension of about 19 m. = 4 0 45' in arc. The direc- 
tion of this star is plotted on the diagram. 
During January the South Pole, moving from N to o, 
increases its polar distance from (3 Hydri by the amount of 
the arc obtained by drawing from o a line at right angles to 
the line drawn from p Hydri through N, and measuring from 
N to the intersection. This arc by scale is slightly over 5". 
Recorded observation gives 5”*2 for the increase in south 
polar distance during January. 
When the pole is moving from Q to R, during April, it is 
moving diredtly away from p Hydri, and consequently in- 
creases its polar distance by the amount of the arc Q R. 
This arc measured off scale is about 11". The recorded 
change in the “ Nautical Almanac” for April is also 
about 11". 
When the pole is moving round that part of its arc 
between T and u, it is moving at right angles to the line 
joining the pole and (3 Hydri, at which date there will be no 
change in the polar distance of this star. Recorded observa- 
tion shows that at about the 20th of July the polar distance 
of p Hydri does not change. 
The polar distance of p Hydri between January 1st and 
the end of July will have increased by the length of the arc 
u N, which measured off scale gives slightly more than 51". 
Recorded observation gives the increase in polar distance 
from this star, between July 20th and January 1st, as 5i' *2. 
The other changes in polar distance, and also the changes 
in right ascension, as demonstrated by this curve, will be 
found to agree with observation. 
The southern star a* Odtantis is plotted, as regards its 
direction, on the diagram. This star, it will be seen from 
the diagram, increases its polar distance until the end of 
March, when the line from the star to the pole at q is at 
right angles to the arc then traced by the pole. Examine 
the “ Nautical Almanac,” and the same facfts will be found 
recorded, as having been found by observation in the Southern 
Hemisphere. 
When the pole is at w, on Odtober 1st, the pole is moving 
at right angles to the arc joining the pole and the star ; 
consequently the polar distance of the star at that date will 
not vary. It is recorded, in the “ Nautical Almanac,” that 
the polar distance of this star does not vary at that date. 
From these results, and those derived from every other 
star near the poles, it is found that the two curves given 
above are the corre<ft curves apparently traced by the poles 
