432 Mr. atwood’s Theory for the Menfuratlon 
the index fhall point to fome degree near to 180°, which is 
done by making that inclination very little more than one- 
fourth of the anode to be obferved. 
O 
33. The tables 1. and 11. are calculated for taking the 
diameters of the fun and planets : the conftrucrion being formed 
on the principles which have been explained (art. 16. 17. iS. 
31. 32. fig. 12. 13.) The fixed plane of reflection is coinci- 
dent with the primitive fecondary, and confequentlv n = o : 
the common inclination of the refleftors to the plane of mo- 
tion — 1 o' ; and the conftant angle of incidence on the fixed 
fpecuium = 7 0 . 
TABLE II. 
1 
Arc- 
pointed to 
by the 
index. 
Ubierved 
angle. 
Diff. 
/ n / /// 
3 ° 3 2 5 ‘ 
IOO° 
// m 
1 3 2 8 
IOI° 
30 46 19 
13 20 
102° 
30 59 39 
1 3 12 
I0 3 ° 
31 12 5 1 
*3 3 
IO4 0 
3 1 25 54 
. 12 54 
i° 5 ° 
3 1 3 8 
12 46 
O 
'O 
O 
t-i 
3 1 5 i 34 
12 37 
0 
O 
32 4 11 
12 28 
O 
CO 
0 
4 
32 16 39 
12 19 
109° 
32 28 58 
12 1 1 
I I o° 
3 2 4 i 9 
TABLE I. 
Arc 
pointed to 
by the 
index. 
Obferved 
angle. 
i° 
/ // m 
0 20 47 
2° 
0 4 1 34 
3 ° 
i 2 21 
4 9 
1 23 8 
5 ° 
i 43 54 
6° 
2 4 40 
7 ° 
2 25 25 
8° 
2 46 10 
9 ° 
3 6 54 
O 
O 
3 2 7 37 
Diff. 
// 
20 
/// 
47 
20 . 
47 
20 
47 
20 
46 
20 
46 
20 
45 
20 
45 
20 
44 
20 
43 
The 
