[ IJ 4 ] 
Obferved zenith 
: ill . of Ardturus. 
Baro- 
meter. 
Thermo 
meter. 
Refrac- 
tion. 
Aber- 
ration. 
Nuta- 
tion. 
Precef- 
fiorn 
Obfervations 
reduced. 
1 766. 
O 
/ U 
// 
// 
n 
// 
O 
/ /' 
May 13, 
14 20,7 
2<M 6 
43 
34>9 
— ’>9 
— 7 > 6 
-f 2 
3 1 
14 48,1 
2 1 . 
31 
14 23,1 
29,8 1 
46 
3 S’* 
— 0,2 
- 7»6 
+ , »7 
3 i 
14 52^ 
2 2. 
31 
14 l 99 
29,67 
49 
34=7 
0 
- 7=6 
+ i>6 
3 i 
14 +3,6 
June 23. 
3 1 
14 20,3 
29,90 
70 
33 > 1 
+ 6,4 
— 7=7 
— 0,1 
3 i 
2 4 32,3 
Mean 
3 i 
*4 S °’3 
Error of the line of collimation 
+ 2,6 
Mean zenith diftance of A ret urns, June 2J 
ON 
ON 
. . 
3 1 
14 52,9 
Mean zenith diltance of the Sun’s center, J 
une 21, 
1766, 
28 
1 1 16,6 
Mean diftance of Ardturus from, the Sun’s 
center. 
^766, 
3 
3 3 6 >3 
From the foregoing obfervations, it appears that 
the mean folftitial zenith dihance in fummer was as 
follows. 
Variation in 100 years. 
0111 
// 
1743. 28 II 2,8 
60 
1746. 28 ii 4,1 
62,5 
3748. 28 ii 4,1 
69,4 
1766. 28 11 16,6 
And, by comparing the three former with the 
latter, the variation of the obliquity of the ecliptic in 
100 years is as is expreffed in the lafi column of the 
table. 
By comparing the diftance of Ardturus from the 
center of the Sun in 1743, with the fame diftance as 
obferved in 1766 (an allowance being made for the 
proper motion of the ftar during the interval, as alfo 
for its variation in declination arifing from the pre- 
cefiion 
7 
