6 RESEARCH IN CHINA. 
SURVEYS IN CHI-LI AND SHAN-SI. 
PAU-TING-FU TO T’ANG-HIEN. 
Stadia Traverse.—The city of Pau-ting-fu, south of Peking, is on the 
line of the Belgian railway, and the position of its northern gate tower 
has been determined astronomically by the British Intelligence force as 
being lat. 38° 51’ 26”, long. 115° 30’ 53”. We were thus able to obtain 
an adequate datum for elevation and a fixed point from which to start 
the survey. A base line was measured on the railroad and the attempt 
was made to expand from it, with the theodolite, to prominent points in 
the foothills on the western side of the Great Plain. Although the dis- 
tance is probably not more than 25 or 30 kilometers we could not see the 
heightson account of the dust in the atmosphere, and our hopes that the air 
might clear were not likely to be realized for two or three months, so the 
natives said. Finding it impossible to see more than 5 to8 kilometers across 
the dead level of the featureless plain, and being obliged to proceed at 
once, we were forced to give up the initial idea of triangulation from Pau- 
ting-fu and to adopt a stadia survey until we should come within sight 
of the hills or into a clearer atmosphere. 
Special precautions were taken in running this stadia traverse, as it 
was considered an element of the continuous system, which was to be 
extended from Pau-ting-fu to T’ai-ytan-fu and was to be the check for 
longitude between these two points. In order that the alinement or direc- 
tion might be platted with precision, the line was run with fore and back 
sights and was furthermore oriented with reference to a sharply defined 
distant object. With the table in the first position an object some 2 or3 
miles ahead was chosen, toward which the line was run. ‘The rod was 
sent ahead and lined in exactly with this distant object; the length of 
the sight was then read from the stadia rod and the difference of eleva- 
tion taken, and then the table was moved to the point occupied by the 
rod. Here the table was again oriented by the distant object and checked 
by a back flag which was at the station just left. In this way the line 
was run as far as possible precisely in one course. When a change became 
necessary a new distant bearing was selected and the line run straight 
toward it until another direction had to be pursued. In order to check 
the distances read and the platting on the sheet, a number of objects on 
the side were intersected from four or five stations. As an additional 
check on the platting, every mile or so the sum of the reading was com- 
pared with the distance platted. Great care was taken with the levels 
as well as with the distances, the length of the sights being reduced to 
400 and 500 feet during the heat of the day, when the air became unsteady. 
