34& Dr. Brinkley’s observation* for investigating 
supposing the constant of aberration for each star the same, 
two results in Table 1 should not differ nearly so much as 
by 1 ", on account of the great number of observations used 
in deducing the results of that Table. 
The discordances between my observations and those made 
at Greenwich may, by some, be considered as showing the 
great precision of modern observations, when it is understood 
that the whole extent of the absolute difference between 
the results of the observations of the Astronomer Royal, and 
of those made here, is only about one second. But, indepen- 
dently of the interest of the question of parallax, it is highly 
important to ascertain the origin of this small difference. It 
may instruct as to the limit of accuracy actually to be attained 
to, when apparently there should exist no limit. 
It will also appear, should any of the results that I have 
found be inexact, that the delicacy of an instrument cannot 
be appreciated by giving correctly some of the smaller mo- 
tions, real or apparent, that occur, because the same instru- 
ment may, as to others, entirely mislead. Whatever may be 
the ultimate determinations, it is hoped, that the long and 
tedious exertions that have been used in obtaining these 
results, will not be found to have been entirely without use. 
