46
PRECISE LEVELING IN THE UNITED STATES, 1903-1907.
OLNEY TO CHAMPAIGN, ILL.
This line was run in 1906 by T. A. Green, over the Wabash Railroad. Con
nection was made at Olney with two bench marks of the Coast and Geodetic Survey.
The observed difference between these bench marks by the Coast and Geodetic
Survey in 1882 was B 3 —11= + 1.7402 meters. The difference of elevation by the
United States Geological Survey in 1906 was 5.767 feet=1.7578 meters, a dis
crepancy of 17.6 millimeters on a distance of 0.4 kilometer. This shows probable
movement of one of the bench marks. The elevations in the computation of the
line by the United States Geological Survey were based on B 3 , and it appears prob
able from its position that it is more stable than B. M. II. It was adopted as the
junction point in the adjustment of the level net.
Connection was made at Champaign with two bench marks established in 1905
and they were found undisturbed.
The principal maximum values of the total discrepancy (B — F) in the main
line were :
Distance.
B-F.
1
B — F per
kilometer.
miles, km.
ft. mm.
mm.
27.1= 43.0
+0.123=+ 37.5
+0. 80
52.1 83. 8
+0.169 + 51.5
+ .61
107.0 172. 2
+ 0.334 +101.8
+ .59
123.1 198.1
+0. 387 +118. 0
+ .60
CHILLICOTHE TO COLUMBUS, OHIO.
This line was run in 1905 by E. L. McNair, over the Norfolk and Western Railway.
It was connected with the Coast and Geodetic Survey leveling at Chillicothe on one
bench mark. The principal maximum values of the total discrepancy (B — F) in
the main line were:
Distance.
B-F.
B—F per |
kilometer.
Distance.
B-F.
B—F per
! kilometer.
km.
mm.
mm.
km.
mm.
mm.
22.0
+ 10.0
+0. 75
72.0
-1.8
-0.02
62. 8
+ 8.4
+ .13
At end 79. 2
+ 2.4
+ .03
PORTSMOUTH TO CHILLICOTHE, OHIO.
This line was run in 1906 by N. A. Campbell and W. H. Monahan, over the
Norfolk and Western Railway. It was connected with the Coast and Geodetic Sur
vey leveling at Chillicothe, on one bench mark, and at Portsmouth with the leveling
along the Ohio River, on one bench mark.
