2 9 0 
Dr. Brinkley on the 
late in the evening. An increase of temperature, therefore, 
relative to a Cygni takes place, and the seconds in a Cygni 
become less than they would have been had the temperature 
remained the same as in the night. The sum of the seconds 
of a Cygni and (3 Aurigas is diminished by this cause, and it 
would be increased by the effect of parallax. Hence this 
cause tends to conceal the effect of parallax in winter. In 
summer the passages of Cygni and (3 Aurigas are reversed 
as to noon, and the sum of the quantities increased by tern- 
perature and decreased by parallax. 
This explanation, if justly founded, will have a tendency 
to diminish the value of stars nearly opposite in vr, which 
Mr. Pond so judiciously selected, and by which he avoided 
any uncertainty from differences of parallax. As to l Cygni, 
the winter observations, Mr. Pond remarks, are far from 
satisfactory ; and they seem too few and too discordant to de- 
cide any thing, even supposing we were certain of the annual 
variation of ^ Cygni, and that it had no visible parallax. 
I shall now proceed to state briefly the results of my obser- 
vations up to the present time, which appear to point out 
parallax as to a Cygni, « Aquilas, and a Lyras; also the results 
of observations of <y Draconis. 
ct Cygni 
The winter observations of this star cannot be materially 
affected by any uncertainty in the maximum of aberration, 
being made nearly equally on both sides of the time when 
parallax is greatest, and aberration = o. But the summer 
observations being generally made after the time when aber- 
ration, in declination = o, the effect of a less maximum of 
