6 4 
Dr. Brinkley on the 
the Catalogues of 1823== — o",io. Now, supposing for a 
moment these differences are errors belonging to the Green- 
wich instrument ; that is, the Catalogue of 1813 is in defect 
= o",47, and the Catalogue of 1823 is o",io in excess. Here 
then the mean southern motion would be reduced by o ", 6 , 
and there would remain only o",5 to be accounted for, half 
of which might be accounted for by a circumstance to be 
mentioned presently. 
The error I suppose in the Catalogue of 1823 is so small, 
that the observations by reflection cannot be adduced to con- 
trovert it ; this, as I have mentioned, could not even be done 
had the supposed error been much greater, in consequence of 
the latitude having been assumed. The observations by re- 
flection have only shown the consistency of the North Polar 
distances, not their absolute exactness. 
The N. P. D. of the Pole Star in the Standard Catalogue 
of 1813 0 , „ 
-1 41 21 ,6 
1 o years variation = ) 
„ > — 3 14,6 
19 ,457 x 10 .... 3 L_ 
Predicted, 1823 1 38 7,0 
Observed, 1823 1 38 7,5 
0,5 South.* 
Mr. Pond has not remarked this apparent southern motion 
of the Pole star, which is so nearly equal to the sum of the 
mean differences of the Greenwich and Dublin Catalogues of 
1813 and 1823. It is highly probable, that this apparent 
southern motion of the Pole star has arisen from small errors 
in determining the place of the Pole star at each period. 
Excepting error, if any, from lunar nutation. 
