Geological researches in China, Mongolia, and Japan, during the years 1862-1865.

PLATE 2.
SEE CHAPTER IV.
Route Map of the Yang Ho District.
This map is intended to show roughly the geological and topographical features of a portion of the
boundary between the Great Plateau of Central Asia and the mountains of China.
The survey was made by the author from observations with a dioptric compass, the distances being
measured by timing a horse whose gait was well known. The work was plotted in the field
on a Mercator basis. The route followed in the mountains, immediately west of Peking, is
not indicated; on the rest of the map, from Changkiakau (Kalgan) westward, it is marked by
the, generally zigzag, line running through most of the villages. Going westward from
Changkiakau (Kalgan) by the northern, and returning by the southern route, the plotting
overlapped at Changkiakau by five and a half miles, an excess which represents the final,
uncompensated, error of the work.
The positions of Siuenhwa, Tatung, and Tungching, are from the Jesuit astronomical observations;
that of Peking is from those of the Russian astronomers.
The section lines of Plate 3 are represented on this map.
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