National Institute of Informatics - Digital Silk Road Project
Digital Archive of Toyo Bunko Rare Books

dust-haze proved a special source of trouble in this respect within and along the deserts of
the Tārim and Su-lo-ho basins, while in the Nan-shan ranges to the east cloudy and rainy
weather prevailed during most of the time devoted to their survey in the summers of 1907
and 1914. During the late autumn and winter months which were otherwise the best season
for survey operations along the northernmost K'un-lun range between the longitudes of
Khotan and Lop-nōr, the extreme cold experienced at high elevations made work with the
theodolite particularly trying.
In addition to the considerations already mentioned, the total absence of local resources,
Marching distances. often even of water, both in the deserts and mountains, obliged us to
move quickly. The rapid succession of daily marches, often over 25
miles in length, which such conditions entailed, is illustrated by the
fact that during the two years and four months which on my second expedition were spent
on Chinese soil and used for survey work, there were 488 shifts of camp, the aggregate of
marching distances for the same period amounting in my own case to close on 8300 miles.
On the third journey when the corresponding period was just under two years, the
rate of progress was practically the same, the total length of my marches on Chinese
soil being close on 7000 miles, and that covered by R. B. Lāl Singh, my indefatigable chief
surveying assistant, probably even more. In addition it should be borne in mind that time
spared for prolonged halts was absorbed mainly by exacting archæological labours, carried
on generally at desert sites and involving further detail surveys.
Observations for longitude would not have been practicable under such conditions,
Uncertainties in and chronometers would not have been reliable. That our equipment
longitude. on the third journey did not include an apparatus for receiving wire-
less time signals must, however, remain a matter of special regret to
me. Its use would have obviated those considerable uncertainties in longitude inseparable
from plane-table surveys extending for great distances mainly from west to east and checked
by triangulation only for a comparatively small portion of their length.
Apart from heights measured by theodolite during the triangulation, altitudes were
Altitude observations. obtained by Watkin mountain aneroids of the Survey of India. Those
used on the second and third journeys were checked at intervals with
two mercurial mountain barometers and, as judged by this test, preserv-
ed a very uniform rate of index error. None of the mercurial barometers survived the trials
of the journeys. One, however, of those carried on the third journey was brought back safely
as far as Kāshgar and could be compared there with the instruments of the fully equipped
Russian meteorological station before it, too, succumbed on its way across the Kara-koram
passes. In addition hypsometrical observations were concurrently taken with boiling-point
thermometers, some of which were kindly lent to me by the Royal Geographical Society.
In the course of plane-table work on mountainous ground clinometers were regularly used
during the second and third journeys to secure readings to prominent intersected heights.
On high elevations special care was taken to obtain clinometric readings preferably from
points where the mercurial barometer was available for observation of absolute heights.
With the object of covering as much geographically interesting ground as possible,
Detaching of surveyors. I detached my topographical assistants from my own party for independ-
ent work whenever practicable routes, means of transport, the attitude
of the Chinese administration, etc., allowed it to be done with a
reasonable degree of safety. During such periods of detachment which on occasions extended
over several months, I carried on the plane-table work along my own routes myself. The
comparison of the positions indicated by our traverses at the points where the surveyors and
my own route-lines crossed or joined, provided a useful means of controlling the results.
Wherever we moved together, plane-tabling was done under my direct supervision
Record of surface and with my assistance. The latter was particularly needed in order
features. to secure a systematic record of such geological or physiographic
surface features as belts of desert vegetation, living or dead; drift-sand
formations stationary or liable to movement; tamarisk-bound sand-cones; ridges and mounds
produced by wind-erosion; salt-encrusted ground of different types, etc., which are charac-