2^6 Dr. Brinkley’s observations for determining 
In the paper which I had the honour of presenting to the 
Royal Society last year, I mentioned my doubts as to the quan- 
tity of the maximum of the aberration of light, and that, as far 
as could be ascertained from Dr. Bradley’s Wanstead obser- 
vations with a zenith sector, we ought rather to adopt 20", oo 
than 20", 25. I also mentioned that it would be desirable to 
investigate this point, and therefore during the last year, I 
instituted a course of observations for this purpose, and I beg 
leave to offer the results thereof. 
No. Ob. 
1 
Max. Aber. 
N P. D. 
By Observations 
in 1818 . 
N.P.D. 
Before. 
a. Cassiopese 
22 
/• 
20,72 
0 / 11 
34 2 7 43>34 
43>59 
Polaris 
2 3 
20,73 
1 39 44>55 
44,27 
a. Ursse Maj. 
2 3 
20,04 
27 16 7.50 
7,38 
y 
2 7 
21,20 
35 17 3+> 8 3 
36,22 
£ 
3 ° 
21,36 
33 3 °> 26 
<M 5 
K 
20 
20,15 
34 7 I 5 ’ 3 ! 
17.63 
* 
21 
21,12 
39 4 6 2 9> I 5 
2 9 37 
166 
20,80 
By these the maximum appears to be 20", 80, which is much 
greater than I had expected. While these observations were 
going forward, Mr. Bessel's work above mentioned was 
published. From several investigations in the Greenwich 
observations of Dr. Bradley, he also deduced the maximum 
= 20", 70, nearly. These results certainly appear extraor- 
dinary, and are not likely to be acknowledged by astrono- 
mers, unless they shall be established by a great number of 
observations. 
My results were computed with great care, allowances 
being made for the ellipticity of the earth’s orbit. It is not 
likely, supposing the velocity of the light of all the stars 
