MANIPULATION OF THE TELESCOPIC ALIDADE 
131 
Table showing angular values of Beaman intervals'^ 
NUMBER OP 
ANGLE 
DIFFERENCE IN 
NUMBER OP 
ANGLE 
DIFFERENCE IN 
INTERVAL 
o 
' 
INTERVAL 
' 
MINUTES 
0 
00.00 
34.38 
36.16 
1 
0 
34.38 
34.39 
16 
9 
19.89 
36.42 
2 
1 
08.77 
34.42 
17 
9 
56.31 
36.70 
3 
1 
43.19 
34.47 
18 
10 
33.01 
37.00 
4 
2 
17.66 
34.52 
19 
11 
10.01 
37.32 
5 
2 
52.18 
34.59 
20 
11 
47.33 
37.71 
6 
3 
26.76 
34.68 
21 
12 
25.04 
38.08 
7 
4 
01.44 
34.77 
22 
13 
03.12 
38.49 
8 
4 
36.21 
34.88 
23 
13 
41.61 
38.95 
9 
5 
11.09 
35.02 
24 
14 
20.56 
39.44 
10 
5 
46.11 
35.16 
% 
15 
00. OQ 
^39.97 
11 
6 
21.27 
35.33 
26 
15 
39.97 
40.54 
12 
6 
56.60 
35.50 
27 
16 
20.51 
41.16 
13 
7 
32.10 
35.71 
28 
17 
01.67 
41.85 
14 
8 
07.81 
35.92 
29 
17 
43.52 
42.58 
15 
8 
43.73 
30 
18 
26.10 
*Reproduced by permission from Metro Manual, Bausch and Lomb Optical 
Co., Rochester, N. Y., 1915, p. 114. 
revolution deflects the telescope about 34 minutes, so that if the 
unit of measurement be 1/500 a revolution of that screw, the 
accuracy of reading vertical angles is greatly increased. This 
is especially important in determining the difference in elevation 
of a station two to eight miles distant as is frequently done in 
triangulation work. The Stebinger gradienter drum surround- 
