constructing a catalogue of fixed stars. 411 
ployed for the other stars. When the whole catalogue is 
completed, these two results are to be examined ; and, if they 
appear equally distant from the pole, the catalogue is affected 
by no common error ; but if, on the contrary, the polar point 
is not found to be precisely between these results, then half 
the difference will be the common error. 
The details of these computations will be found in the 
Greenwich observations ; and it will there be seen that the 
polar distances of this star, determined by 158 observations, 
in the same manner as any other star of the catalogue, 
namely, by the application of the common index error, was 
found to be - - - 1.41.21.50 
Below the pole, by 132 observations, computed 
in the same manner = 358.18.38.32 
Their sum - - 359 59 59 - 8a 
360 
Difference from 360 - 00 o".i8 
Difference or common error = 0.09 
This difference, o".oy, is the common error to be added to 
each star of the catalogue, and the polar distance of the star 
thus corrected will be 1.41.21.59. 
I find by about 350 observations, deduced in the usual 
manner, without any reference to the other stars, 1.41.21.65, 
reduced to the beginning of 1813. 
The same principle, which I have thus attempted to explain, 
may be applied with equal facility, and even greater advan» 
tage, to the formation of a catalogue in right ascension. The 
MDCCCXVIII. 3 H 
