TOPOGRAPHIC SURVEYS. 7 
This traverse was commenced from the north gate of the wal! at Pau- 
ting-fu, and was run to the base of a pagoda on a small isolated hill about 
11 kilometers east of T’ang-hién and 4o kilometers from the starting point. 
It is probable that the error in distance will not exceed 350 meters and the 
level should be within 3 meters. The number of stations occupied was 
173 and the average length of the shots was 226 meters. The survey was 
executed during four consecutive days, from January 3 to 6. 
T’ANG-HIEN TO T’AI-YUAN-FU. 
Graphic Triangulation.—T’ang-hién lies near the western margin of the 
Great Plain, in the immediate vicinity of low foothills of the mountains 
which extend from the province of Shan-si into that of Chi-li. Our route 
lay due west across these mountains to Wu-t’ai-shan, and thence south- 
ward among the ranges to T’ai-yiian-fu. Although the conditions of the 
atmosphere made it impracticable to execute that larger triangulation 
which we had hoped to carry out with a theodolite as a primary control 
for the graphic triangulation, we nevertheless deemed it expedient to begin 
the latter. 
A base line about 3 kilometers in length was measured with the steel 
tape on the plain west of T’ang-hién. One end was established on the 
northwest corner of the city wall and the other was marked by a temporary 
signal. ‘The exact position is indicated on the map, sheet F I. With the 
aid of Chinese assistants two measurements were made which checked 
within .85 meters. Since this line was to be platted on the plane-table sheet 
on a scale of 1:go0000, the difference between these two results was 
not measurable on the map and the distance was accepted as sufficiently 
accurate. Signals were built on several neighboring heights, appropriately 
chosen to give good triangles, and the graphic triangulation was begun 
by occupying the base stations and these neighboring points. The network 
of triangulation can be traced on the atlas sheets, the exact points occupied 
as stations being indicated by a small triangle. 
Had it been practicable it would have been desirable to build monu- 
ments upon the triangulation points in advance, in order to give definite 
objects on which sights might be taken, but we frequently were unable 
to learn, even from the natives, the exact direction in which we were to 
travel for a few miles ahead, and there was no one available who sufficiently 
understood the objects of the work to be sent ahead to construct monu- 
ments. Moreover, it had been the experience of Mr. Willis in Shan-tung 
that monuments which had been erected at a station in order to mark 
the exact point that had been occupied, had been thrown down over 
