OODE.] 
TRANSIT AND STADIA WORK. 
43 
iave been applied to the distance obtained and used on this section, 
me being that for reduction to sea level, amounting to -8 feet, 
tnd the other that for reduction on account of tape, which, alter com- 
xarison with the United States Coast and Geodetic Survey standard, 
v&s found to be +12 feet. Thus, theoretically, the monument w&a 
)laced 4 feet too far north, but the error, compared with thai which 
uight result from unavoidable station error, is so small that it may 
>e considered as negligible. 
It might be well to explain what is meant by " station error." It is 
he error which is more or less inherent in all astronomic determina- 
ions, being caused by the deviation of the plumb bob, on account of 
-arying local attractions, from the true vertical. Its existence may 
>e detected by direct measurements between two astronomic si at ions. 
Assuming an astronomic location to be made at J., a connection by 
riangulation with another station, B, and the position of B thus 
.educed from that of A, then if the astronomic position of B is deter- 
mined, the discrepancy between the astronomic position and the posi- 
ion determined by triangulation from A represents the combined 
tation error. Efforts have been made to deduce a law, based on the 
ontour and density of adjacent land forms, which shall define the 
mount of attraction affecting the plumb bob which might be expected 
a any particular case, but nothing satisfactory has been accom- 
•lished, owing principally to the fact that it is impossible to give an 
ccurate value to the various components which constitute the mass 
f any given section of the earth's crust. 
The following table gives the results obtained directly from the 
tadia, and which were used in reducing the random line to the true 
ne, both in distance and in azimuth. These figures do not, however, 
epresent the degree of precision obtained by the stadia in measuring 
he distances, as they are unaffected by any corrections. 
'able showing discrepancy between computed and measured distances, also discrep- 
ancy in azimuth. 
Sec- 
tion. 
Sta- 
tions. 
Com- 
puted 
distance. 
Stadia 
distance. 
Latitu- 
dinal dis- 
crep- 
ancy. 
Discrep- 
ancy. 
Longitu- 
dinal 
discrep- 
ancy, 
random 
line west 
of true 
line. 
Discrep 
ancy. 
Mean an 
gular 
error in 
azimuth. 
1 
2 
3 
0-154 
154-800 
800-949 
Feet. 
62,276 
228,734 
49,190 
Feet. 
62,071 
228,014 
49,132 
Feet. 
205 
720 
58 
1 in 304 
1 in 318 
1 in 848 
Fet t 
10 
71 
12.5 
I In 6,238 
1 in 8,228 
1 in 8,921 
O ' " 
n ii 88 
u 1 oi 
ii ii 68 
The distances measured by the stadia should be corrected before any 
itisfactory comparison can be made with the computed distances for 
le purpose of testing the accuracy of the stadia work. 
Two conditions will be considered. The first is based upon the 
