TOPOGRAPHIC SURVEYS. 9 
The results of these two measurements were respectively, as follows: 
MILES. KILOM’S. 
Length of check base, as determined by graphic triangulation, extended 
from the initial base line at T’ang-hién and measured as nearly as 
possible on the field sheet on a scale of of 1:90000................ 4.74 7.62 
Length of check base, as determined by triangulation with theodolite 
from special short base measured for the purpose ..............-..- 4.68 iste} 
DIR CLE Ce iene Petey ores temic ic ahate re a doled on a ae snepareie tra Gneoe anes .06 .09 
This result justifies confidence in the positions determined by triangula- 
tion. We consider them as reliable as the astronomical observations, 
with which they compare closely. The following table gives the positions 
for which we have determinations by both methods: 
TABLE OF LATITUDES. SHOWING RESULTS BY GRAPHIC TRIANGULATION AND BY 
OBSERVATIONS ON POLARIS. 





Position by graphic Position by 
Place. triangulation observation on Polaris 
North latitude. North latitude. 
| 
Average. 
Witt alashatt ter eee 30.) 00.) .06" Te eC, 15, 307, GG" 18" 
Wi-tai-hién........2-2. Boo La On” eat ‘ oe meee GL! 
Fikes Grey nee 
ELUNE Se pera ae eis haere 38° 19’ 49” B80 20,0 59" 38° 20’ 44” 
Bk yee ee 
370,525) 26°] 
° 5’ 2 u 
ae VATIT 2% ote a sladoee-e Zinhee Nee ara 4 ae oe orf 372) sal 35” 
37° 52° 440" J 




If the above positions be compared it will be found that at Wu-t’ai- 
shan the difference is 12”, at Wu-t’ai-hién it is 16”, and at Han-yang 55”. 
Unfortunately an exact comparison cannot be made for T’ai-yiian-fu, as 
the astronomical observations were made in the inn in the heart of the 
city, and it was found impossible to locate it exactly with reference to the 
triangulation. As nearly as we can tell, however, the difference there is 
between 20” and 30”. In all cases the position as determined by graphic 
triangulation is south of that by latitude observations, and the difference 
between the two seems to increase, at least to Han-yang. ‘There is some 
reason to think that any error in triangulation was augmented between 
Wt-t’ai-hién and Han-yang, as the atmospheric conditions were very 
unfavorable on account of high winds and dust storms in that loess-covered 
district, and the wide expanse of the Hin-chéu basin was a serious obstacle 
to progress. But on their part the latitude observations lack refinement, 
since the verniers of the theodolite were graduated only to the nearest 
15”, and they are also liable to a’station error on account of deflection of 
the plumb-line among the high mountains. On the whole we consider the 
results of the graphic triangulation to be consistent and reliable. 
