REPORT ON ASTRONOMY. 
141 
ing stars of nearly the same declination and different right as¬ 
censions. This was done at Greenwich, and still the observa¬ 
tions gave no indication of parallax. Dr. Brinkley still main¬ 
tained its existence; and for several years each successive vo¬ 
lume of the Phil. Trans, contained a paper on one or the other 
side of the question. In the course of this discussion, the de¬ 
fects of the different instruments, and of the different correc¬ 
tions were closely examined, and in this respect Astronomy has 
certainly been advanced by the controversy. In the Phil. 
Trans. 1821, Dr. Brinkley investigated from observations, by 
the method of equations of condition, the quantities of aberra¬ 
tion, nutation, and parallax, and found sensible values of pa¬ 
rallax for several stars, especially for « Lyrse. Mr. Pond still 
doubted of this result; and in vol. i. of the Mem. Ast. Soc. Dr. 
Brinkley endeavoured to show that the Greenwich observations 
themselves afforded evidence of parallax. In the Irish Trans¬ 
actions for 1825, Dr. Brinkley attempted to settle the ques¬ 
tion by an instrumental investigation of the most delicate kind. 
The quantity of solar nutation (which had never before been 
extracted from observations,) being smaller than that which he 
attributed to parallax, it seemed that if the observations were 
competent to exhibit the former, they might assuredly be relied 
on for the latter. By equations of condition, therefore, he 
investigated the quantities of aberration, solar nutation, and 
parallax, for different stars, and obtained consistent results for 
the solar nutation, and sensible quantities for parallax. This 
result would have appeared to me decisive, but for a difficulty 
which another investigation has made to appear. In the Ast. 
Soc. Mem. vol. iv. is a most valuable investigation of the quan¬ 
tity of aberration as deduced from a vast number of Greenwich 
observations, by Mr. Richardson, Assistant at the Greenwich 
Observatory. The mean result (20 /, *50) appears to me the 
most accurate that has yet been obtained. But from different 
stars different values are obtained ; and it is remarkable that 
the difference between the values for y Draconis and Ursse 
Majoris,—stars less affected than almost any other by uncer¬ 
tainty of refraction,—is of opposite kinds in the two determina¬ 
tions of Brinkley and Richardson, and that the discrepance far 
exceeds the quantity which Dr. Brinkley had proposed to 
investigate. The existence of sensible parallax appears to me, 
therefore, to be yet undecided.—A few observations and re¬ 
marks on parallax may be found in Bessel’s Fundamental and 
Struve’s Observations. 
Mr. Pond in the mean time had remarked {Phil. Trans. 
1823), that many fixed stars appeared to have an accelerated 
