100 Astronomical and Nautical Collections. 
The comet of 1766, which has been suspected to be the same, is 
recorded to have been very bright to the naked eye, and its motion 
was retrograde. 
iii. Comparison of the Nuw Tasirs of Refraction with 
Observation. 
Rerractions observed by Mx. GroomBrince. (Coll. XTIT.i.) 
M.Corr. Red. to Ivory 
Obs. App. Alt. Fahr. forl®  Refr. B.30 469.5 N. A. Error. 509. Error” 
16 218 49.6 49.2 $.5 2223.3 99 39.7 22 16.2 —16.5 22 10.2 —10.8 
25 @& 30. 9,5,.38.1 3.3. .91,38.0,.91 10.2 2), 6.1 — 4.1.20 58.7 = 7.2 
17 2 0 8.1 52.9 2.7 1811.1 18 28.3 18 28.5 +0.2 1819.0 — 0.4 
[44] 217 35.2 31.9 9.4 17 38.9 17 4.0 1710.7 + 6.7 17 1.5 F 2.6 
13 2 3053.4 56.7 2.3 1551.6 1615.0 1618.6 + 3.6 16 8.5 — 2.3 
9 241 2.2 56.3 2.1 15 18.3 15 38.8 15 39.3 + 0.5 15 29.9 — 5.1 
5 2.51 34.5 28.7 2.1 15 32.7 1455.3 15 2.6 + 7.3 14 53.3 414.2 
12 $ 229.9 38.9 2.0 ..14 44.7 14 99.5 14 27.0 —-2.5 1418.0 + 2.7 
10 $6 50;9 54.8 2.0. 19 58:5 14.10... 14.19.98 070) 14) beater 1). 
8 $3 53°87c5, 89.8 1.6. 1217.4. 12 6.7-,12 6.2 — 0.512 Ove 7. 2,6 
10 “47 “ova "s90°8" 1.56 12+ 1.6 11°40.2- 11 36-2 — 4.0- Itol.9 —t 3.5 
15 449 8.7 °38.6 1.33 10 21.7 1011.2 1016.4 + 5.2 1011.8 + 3.8 
12 455 27.2 43.5 1.30 10100 10 5.4 10 5.2 —0.2 10 1.04 1.1 
16 455 55.7 38:8 1680 10 19.8 109%2.1..10..4,4.>.2.28 On Osim, 5. 1 
+56.8 + 62.6 
+ 1.2 +25.4 
7 5 917.7 58.2 1.25 999.8 944.4 943.0+1.4 9 39.2 #06 
11 5 2758.5 ‘33.8 1.20 928.5 913.8 913.8 +0.5 911.7 + 2.1 
13 5 44 33.2 53.8 1.13 841.4 849.7 853.04 3.3 849.3+0.3 
13 5 4755.9 33.6 1.12 857.5 843.1 847.6 + 4.5 8 44.8 + 1.1 
29 613 12.7 38.5 1.05 820.8 812.4 8162+ 3.8 814.1 +1.8 
23 6 30 26.4 58.3 .98 746.4 1757.5 757.1— 0.4 7551+ 1.7 
7 YG 85.0887 <9 67 g1s4 (7 19.8!) 7 20.5. Oly © Woeeeseol 7 
94 792 13.6 61.8 .88 658.0 711.5 7 60—5.5 7 5.2 + 2.3 
13 8 20 21.3 39.9 .82 636.5 622.9 620.8—2.1 619.9 + 2.0 
Int. Int. 50° 
Br.22 7 $13 66.0 .89 6542 7 84 7 96+1.2 7 8.8 
P.156 1343 0 45.0 .47 $57.0 354.6 354.6 0.0 3 54.9 
The mean refractions of the Nautical Almanac are here com- 
pared with the observations as reduced to the standard tempera- 
ture of 46.°5 for the exterior thermometer, by taking a mean of the 
English and French corrections, for the reasons explained in the 
