26 
SURVEY OF IDAHO-MONTANA BOUNDARY LINE. 
[bull. 170. 
to Divide and Scotchman stations, near the Idaho-Montana boundary 
line were computed. A check azimuth was observed at Divide trian- 
gulation station July 7, 1898, Avith the same theodolite. Twenty 
pointings (direct and reversed) on Polaris were obtained and referred 
to Scotchman station. 
Azimuth of line Divide-Scotchman computed from Spokane base _. 170 18 05.82 
Azimuth of same line by direct observation . _ 170 18 10.25 
Difference 4.38- 
The observed value was adopted in the computation of positions 
in the extension of the triangulation northward to the international 
boundary. 
Examples of record and computation for azimuth determination are 
given herewith : 
Azimuth determinations at triangulation station Divide, July 7, 1898. S. S. 
Gannett, observer. 
m [Latitude (<J») 47° 57' 67".51. Longitude (A) 116° 01' 33".08] 
Azimuth mark. 
PolarisD 
Polaris R 
Azimuth mark. 
Azimuth mark. 
Polaris R 
Polaris R 
Azimuth mark . 
Time. 
h. m. s. 
10 27 52 
10 33 48 
10 42 02 
10 46 08 
Level. 
W. E. 
d. 
13. 
11.8 
d. 
16.0 
18.0 
24.8 34.0 
-9.2 
13.8 
14.0 
15.3 
15.0 
27. 
14.0 
13.5 
30.3 
1.5 
11. 5 
12.0 
27.5 
+ 4 
16.0 
18.2 
34.: 
H 
23.5 
,0 
16.0 
14.0 
30.0 

Microme- 
ter A. 
Microme- 
ter B. 
Mean. 
c ' d. 
221 09 02 
255 33 24 
° ' d. 
41 09 13 
75 34 07 
O / II 
221 09 15 
255 34 01 
75 36 08 
41 09 18 
255 34 21 
221 08 11 
75 35 29 
41 08 59 
78 10 23 
112 39 14 
258 09 09 
292 38 08 
78 10 02 
112 38 52 
292 40 02 
258 09 28 
112 40 11 
78 10 14 
292 40 13 
258 10 12 
Angle. 
34 24 46 
34 26 30 
34 28 50 
34 30 01 
Time by mean time watch, 34 seconds fast on one hundred and fifth meridian 
time. 
One division of striding level = 3". 66; 1 division of micrometer = 2". 00. 
Level correction = — — \ (w + w') — (e +'e') \ tan h; d being the value of a 
division of the level, iv + w' readings of west end of level bubble, e + e' readings 
of east end of level bubble, and h, the angular elevation of star, the foregoing for- 
mula reduces as follows: 
^? X tan 47° 57' 57" (1.11) = 1 ".01. 
