46 
SURVEY OF IDAHO-MONTANA BOUNDARY LINE. [bull.17( 
Table showing discrepancies between stadia distances affected by "/+ c" correctio 
and computed distances. 
Sec- 
tion. 
Stations. 
Stadia dis- 
tance re- 
duced to 
mean sea 
level. 
Correc- 
tion for 
f+c 
Corrected 
distance. 
Computed 
distance. 
Discrep- 
ancy add 
to stadia 
distance. 
Discrepancy. 
Feet. 
Feet. 
Feet. 
Feet. 
Feet. 
1... 
0- 154 
62, 061 
+ 146 
62, 207 
62, 276 
+ 69 
1 in 903 
2___ 
154- 800 
227, 967 
+614 
228, 581 
228, 734 
+ 153 
1 in 1,495 
3... 
800- 949 
49, 119 
+ 142 
49,261 
49, 190 
- 71 
1 in 693 
4___ 
949-1,046 
33, 058 
+ 92 
33, 150 
33, 174 
+ 24 
1 in 1,381 
The mean discrepancy for the whole distance is 175 feet, or 1 in 
2,133. This, it will be observed, approximates that obtained after 
application of the stadia-factor correction. 
The results from the application of the f+c correction serve to 
indicate that the rod was graduated approximately correctly, as in- 
tended, and the stadia wires were fixed so as to read distances on the 
rod approximately in the proportion of 1 to 100. As the stadia-factor 
correction was systematic, the results obtained for distances along 
the boundary line by a direct adjustment of the original stadia dis- 
tances to fit the triangulation exactly correspond to those which would 
have been obtained if the stadia-factor correction had been first applied 
and the remaining discrepancy afterwards adjusted to the triangula- 
tion. 
The only check obtained with reference to vertical distances or 
measurements of height is that furnished by the portion of the line 
between the Northern Pacific and Great Northern railroads. Along 
the former road is a line of precise levels run by the United States 
Geological Survey from a mean sea-level connection at Tacoma, Wash- 
ington. The stadia line was connected with a bench mark of the pre- 
cise levels, and this bench mark is the datum upon which the elevation 
of the stadia line is based. The profile of the Great Northern Railway 
adjusted to the United States Geological Survey precise levels fur- 
nished an elevation at Leonia to which the stadia line was joined. 
The resulting discrepancy was 73 feet, which is greater than might 
reasonably be expected, but it is possible that some of the error may 
be in the railroad profile. 
The details relating to the profile of the boundary line between 
these two railroads are as follows: Sum of horizontal components, 
201,188 feet; sum of vertical components, 42,700 feet; discrepancy 
in closure, 73 feet; discrepancy referred to horizontal components 
equals 1 in 2,756; discrepancy referred to vertical components equals 
1 in 585. 
Extensive and careful experiments with the stadia were made by the 
