00DE -] BABE LINE AND AZIMUTH. 25 
SPOKANE BASE LINE. 
A Bite for this base line was found in the valley of the Spokane 
fciver, easl of the city of Spokane, points for its expansion being 
ocated on the surrounding hills. The line was measured along a 
angenl of the Northern Pacific Railway, beginning aboul 2.5 miles 
•ast of the Spokane depot and extending eastward 5 miles. Ii was 
>repared i>y nailing boards I by 6 by 60 Inches ;s< ,( > feel aparl along 
he cross-lies parallel to the rail. On eaeli hoard a smaller board 
1 by 1 by L2 inches) was nailed, and on the latter was lacked a strip 
>f zinc 2 by L0 inches. At nighl two complete measurements were 
nade with United states Geological Survey steel tape No. l, tinder a 
ension of 20 pounds, temperature being taken by reading three fcher- 
Qometers al each tape length. The fronl end of the tape was marked 
in the zinc strip with a tine brad awl. The Length of the tape used, 
JOmpared with the mural standard of tlie United States Coast and 
ieodetie Survey on I October 30, 1895, was found to be 300.0075 feet; 
m December 5, L896, 300.0058 feet. The mean of these two, ^0.0067 
'eet. was adopted. 
Adopted coefficient of expansion . . F. . .OOOOOGo 
vtean temperature of first measurement 60 .35 
Mean temperature of second measurement... 59 .25 
Difference between the t w< i measurements, when corrected for tempera- 
ture . .- feet. .000 
Mean elevation of tin- line above sea level, as given by a profile furnished 
by the Northern Pari lie Railway feet. . 1 ,972 
length of base corrected for temperature .. ._ do. . . 26, 107.288 
Correction for inclination do... — 0.156 
deduction to sea level ..do... —2.491 
deduced length . do.. 26,404.641 
Logarithm of Length, in meters. 3.9056962 
The terminal points were transferred to the embankment 25 feel 
until of north rail, and the new points being int ervisible, high tripod 
jupports i'^v the theodolite were necessary. 
AZIMUTH. 
The azimuth of the Spokane base Line was determined by mounting 
5-inch micrometer theodolite N<>. 300 over the wesl base and i 
iring the angle between Polaris and a mark placed at tin- east baj 
^ series of observations, consisting of eighteen pointings (direel and 
•everse), was taken near elongation August L5, L896, the resulting 
nean for azimuth west base-east base being 253 L8' U>".80. 
Willi this value and the astronomic Location of the cupola of the 
»ourt-house at Spokane the positions of all triangulation stations 
unl azimuths of all Lines in the mam belt of triangulation eastward 
teas- 
se. 
