20 SURVEY OF IDAHO-MONTANA BOUNDARY LINE. [bull. 170. 
Mr. Gannett was instructed to carefully examine the topographic 
features of the country adjacent to the triangulation station Divide, 
in order to determine whether it was on the true summit of the Bit- 
terroot Mountains, and then, by traverse from the Divide station, to 
locate the exact point on the summit from which, as the initial point, 
the random line should be projected northward. Observations for 
azimuth were obtained at Divide, the details of which will appear 
hereafter, and also at the end of the traverse line. This traverse was 
run along the divide westward through a longitudinal interval which 
was supposed to be 6,072 feet, but, unfortunately, owing to an error 
in the field computations, the location of the initial point was made 
177 feet too far east. This error was discovered in the office, and 
in the adjustment of the random line it was entirely eliminated from 
the final results. 
Work on the random line was commenced July 11 by the party 
under Mr. Reaburn, which consisted of one recorder, two rodmen, 
two packers, three axmen, and a cook. The region traversed was 
along the entire line very rough and generally covered with timber. 
There were few roads or open trails, and the transportation problem 
was a difficult one. A pack train was provided, and it was generally 
necessary to make long detours and to cut out trails in order to estab- 
lish camps at convenient points near the line. Toward the close of 
the season a great deal of snow was encountered on the high ridges, 
the party narrowly escaping being snowed in without provisions. 
The survey of the random line was completed to the vicinity of the 
international boundary on October 31 in snow 2-J- feet deep. 
Horizontal and vertical distances along the entire line were obtained 
by stadia measurements. The total rise and fall of the boundary line 
was about 63,000 feet, the average length of sights 350 feet, length of 
line about 72 miles, number of transit stations 1,051, and number of 
azimuth stations 17. 
At the conclusion of the field season Mr. Perkins returned to the 
office and Mr. Reaburn was ordered to field duties elsewhere. 
During the office season of 1898-99, after the triangulation had 
been finally computed, an adjustment of the stadia work to the trian- 
gulation was made, and tables were prepared showing the exact lati- 
tudinal and longitudinal corrections to be applied at each station of 
the random line. Elevations were also computed from the vertical 
angles for each transit station. Six sheets on mounted drawing paper, 
each sheet extending through a latitudinal interval of 10', were then 
prepared. On these sheets was drawn the boundary line in its true 
position, and all topographic features which had been located from 
the random line were indicated. Such elevations as would be useful 
in sketching contours were also placed on the sheets, and the sheets 
thus arranged were used for sketching the topography adjacent to the 
line. 
Mr. Reaburn resumed field operations about the middle of June, 
