40 
SURVEY OF IDAHO-MONTANA BOUNDARY LINE. [bull. no. 
DIVIDE (2). 
This triangulation station is not on the meridional portion of the 
line, but on the crest of the Bitterroot Mountains, farther south, and 
was located in connection with the survey of the Bitterroot Forest 
Reserve. 
It is on the main summit of the Bitterroot Range, on the boundary 
line between Montana and Idaho, 20 miles (air line) west of Grants- 
dale. It can be reached from the Lost Horse Pass (camp being at 
Twin Lakes) by following the northwest face of the mountain north- 
east from the Twin Lakes to the crossing of Moose Creek, thence up 
the creek to the Meadows. The peak lies to the northwest, about 
2,000 feet above the meadow. 
Station mark: A rock cairn 5 feet in diameter and 8 feet in length. 
[Latitude, 46° 11' 32".l. Longitude, 114° 28' 12". 2.] 
To station- 
Azimuth. 
Back azimuth. 
Log. distance. ! 
Ward (2) 
El Capitan ... 
279 32 28 
344 06 39 
99 40 31 
164 09 53 
Meters. 
4. 16360 
4. 32652 
TRANSIT AND STADIA WORK. 
The transit used was one manufactured by Young & Sons, of the 
type known as No. 10 mountain transit, the maker's number being 
6838. The horizontal circle was 4f inches, and this circle, as well as 
the vertical circle, was graduated to read with verniers to 1'. The 
instrument was provided with a compass attachment, fixed stadia 
wires, and a tripod with extension legs. The extension legs were at 
times very necessary, as may be seen from PL VI. Two stadia rods, 
of seasoned white pine, three-fourths inch in thickness, 12 feet in 
length, and 4 inches across the faces, were made in Spokane. The 
lower portions of the rods were tapered to a point and shod with steel. 
The design of the rod was black on a white ground. (See fig. 1.) By 
a series of tests the stadia interval was found to be in the ratio of 1 
foot on the rod to 100 feet horizontal distance, as nearly as could be 
determined, and the rods were graduated to even feet and tenths. 
The extreme divisions of the rods included 10 feet, and each tenth 
was divided into five parts, so that hundredths could be easily read 
by estimation. No numbers were placed on the rods. In practice 
the rods were held vertically, proper corrections being applied for 
reducing all sights to the horizontal. 
There was no expectation of obtaining exact independent results for 
distances measured with the transit and stadia upon the basis of the 
stadia wires in the transit being set in the ratio of 1 to 100 and the 
