In going to Lan-chou Fu from Yen-an Fu the Longitudes of Ch’ing- 
yang Fu and Ku-yiian Chou were not satisfactory, as Grant only had two 
watches and the time consumed was too great. In coming back he took 
a second set, which worked out exceptionally well, the rates of the 
watches having been very regular, and the time consumed by the journey 
being comparatively short. The Longitude of Yen-an Fu, as determined 
by the watches, was 109°-27’-33”, and that as calculated from occultation 
previously taken 109°-26/-49”. However, calculating the Longitudes back 
from Yen-an Fu, as a starting point, the biggest variation was 2'. We 
consider the chronometer Longitudes correct to 1 mile. 
The position of Lan-chou Fu (South Gate) was fixed as Lat. 
36°-3'-6"; Long. 103°-40/-54”. This was the only place on our trip where 
we had a subsequent opportunity of comparing our determinations with 
those of another traveller. Mr. Clementi, who travelled from Kashgar 
to Kowloon in 1907-8, gives the position of Lan-chou Fu as Lat. 
36°-3/-11"; Long. 103°-46/-7". His latitudes were taken by N. and S. 
stars and his longitudes by chronometric differences. 
Altitudes. 
After leaving T’ai-yiian Fu all determinations to within 30 miles of 
the Yellow River were trigonometrical (7.e., obtained by vertical angles 
with a theodolite). All subsequent heights are barometric. For baro- 
metric determinations they can be taken as reasonably accurate, as the 
aneroids were frequently compared with the mercurial barometer. The 
mean of the barometer and the boiling-point readings was taken as the 
correct height. 
Previous Surveys. 
Without pretending to give any exhaustive record of previous foreign 
surveys of the country traversed, we offer a slight summary of such as we 
have been able to trace. 
Early in the Eighteenth Century the Emperor Kang-hsi ordered 
a survey of the Eighteen Provinces to be carried out. In this he 
most probably had the assistance of the Jesuit Fathers, whose influence 
during this reign was very great. The Chinese method of map-making 
is to give a separate sheet for each ‘ Fu” or “ Hsien” district, and it 
is of course possible to piece together a number of these sheets to form 
a survey of the whole country. This however leads to a thoroughly 
untrustworthy map, as it is vital “‘to work from the whole to the part, 
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