482 
Dr. Brinkley's remarks on 
distance (about 30°) of a Lyras 3 " greater in the beginning 
of December or February than in the beginning of August 
( these are about the middle times of the winter and summer 
observations). The Greenwich instrument finds, by twenty 
observations in summer, and twenty in winter, the double 
altitude (about 154 0 ) of a. Lyras exactly the same. 
Comparing these naked facts together, the first impression 
would be, notwithstanding the greater number of observa- 
tions at Dublin, that the Greenwich result is more likely to 
be right, because it is more likely that two angles, that are 
really equal, should be found equal, than that two angles, 
really unequal, should be found equal, by the errors of ob- 
servation. 
This is all the admission, that it appears to me, can be 
made. When the collateral circumstances are examined, 
unless I greatly deceive myself, the probability will be found 
in favour of the exactness of the Dublin results ; and I cannot 
but feel surprised, considering the experience Mr. Pond has 
had of the Greenwich circle, that he should attribute such 
weight to these results by reflection. 
But the circumstance which I am going to mention, will 
make it appear certain that the consistency of the Greenwich 
instrument cannot be depended on, to the degree of exact- 
ness, that these observations of a Lyras appear to show. It 
even renders it probable that it cannot be depended on even 
to a degree of exactness sufficient to confirm, or refute, the 
parallax which I have found by the Dublin instrument. 
In the year 1813, 1814, and 1815, the Greenwich instru- 
ment was considered in a perfect state. 
