254 Dr. Wollaston on the [Ocr. 
Diff.R. A. Diff. calc, from N, Alm. 
highs: m 8 mn! (83 
May18 2 40 25 4 25:6 ay 
21 30 50 3 43-1 one 
Borne ky OS 3 38:8 ae) 
19 Ov eke les 3 37 
Diff. Decl. 
May 18 2 44 33 45 56 
23 19 40 40 57 
19 : . : ry 40 36 
Itis evident that, in these observations, the differences between 
the observed and calculated places of the planet are not such as 
to indicate a refraction that can be relied on. 
My own observations were very few in number, and not to be 
compared to the former in precision; but they are necessary to 
supply a deficiency when Capt. Kater was at a distance from his 
instruments, and could make no observation. 
On the 26th, between XJ. 20 and XI. 30 I had three compa- 
tative observations, the best of which gave me the passage of 
Venus 3™ 55% after the sun. The mean of two others bein 
3™ 49°, I consider the result as on the 25th, 234 24m, Dift 
R.A. 3" 52". 
The nearest second to be inferred from the Nautical Almanac 
for this time being 3™ 53° after the sun, it is evident that no per- 
ceptible refraction occurred at this time. 
From the observations of Capt. Kater, no retardation of the 
motion of Venus can be perceived in her progress toward the 
sun, as would occur from increasing refraction ; and by compa- 
rison of her motion in the interval between his last observation 
and my own, with her change of place for the same interval 
given in the Nautical Almanac, there seems no ground whatever 
to suppose that her apparent position has been in the least 
affected by refraction through a solar atmosphere, although the 
distance at the time of Capt. Kater’s last observation was but 
65’ 50” from the sun’s centre, and at the time of my own only 
5a’ 1a". 
Although these distances appear small, I find that Venus has 
been seen at a still less distance by Mons. Vidal of Montpellier 
in 1805.* Onthe 30th of May, he observed Venus 3™ 16° after 
the sun, when their difference of declination was not more than 
1’, so that her distance from the centre was about 46 minutes of 
space. Since his observations also accord with the calculated 
places of Venus, they might have superseded the necessity of 
fresh observations, if I had been duly aware of the inference to 
be drawn from them. 
The same skilful observer has also recorded an observation of 
* Conn, des Tems. 1808. 
