alone could give safe access to Central Asia for trade and political expansion. The high mountains
to the south for them possessed value only as a mighty natural rampart that gave flank protection
for their great western highway, and the care with which I found all routes leading across this ram
part guarded by watch-towers, ` chiusas ', or military posts on passes and at suitable points of
debouching valleys,21 proves that this value is realized to the present day.
But without the ample vegetation which favourable climatic conditions assure to the Central Winter
Nan-shan, and without the advantages of equally abundant winter grazing by the side of the cultivable grazing
area, the territory, relatively limited in extent, could not have offered sufficient attractions to those slopes of
nomadic nations to become, for some of them at least, a main seat of power during successive Nan-shan.
periods. Owing to a combination of geographical factors which it would take too long .to set forth here in detail, the winter grazing just referred to is to be found in plenty along the lower courses of all the more important rivers that drain the northern slopes of, or pass through, the Richthofen Range. It exists, too, in many parts of the foot-hills, and, as my explorations of 1914 showed, in places even on the nearest plateaus of the desert hill chain which fringes the cultivable belt on the north, connecting the Ala-shan with the Pei-shan.
It is only in the light of the geographical features I have endeavoured briefly to indicate that HistoriCal
we can correctly understand what history tells us of the struggles which Wu-sun, Yiieh-chih, and struggles
I-Isiung-nu carried on for the possession of this ground before the advent of Chinese power. They sage land'.
must be kept constantly in view also if we are adequately to appreciate the persevering efforts which alone enabled the Chinese successfully to open up this passage towards Central Asia and the West, and to clear it again after intervals of nomadic invasion.
SECTION IV.—FROM KAN-CHOU TO CHIN-TA
At Kan-chou I had reached on August 27 the easternmost limit of my journey. Practical tasks kept me busy during most of my six days' stay there. Yet I was able to gain sufficient impressions of this large and still flourishing city to realize the importance it must always have claimed in the history of the Kan-su marches. Situated in the midst of an extensive fertile tract to which the large Kan-chou River, or Hui Ho, and two considerable tributaries on the west assure plentiful irrigation, Kan-chou also enjoys other advantages of a geographical nature. Though its elevation, about 5,10o feet above sea-level, is about the same as that of Su-chou, it has a distinctly more favourable climate, receiving more rain in the summer months and being less exposed to icy winds from the desert on the north during winter and spring. This latter advantage may partly be due to the protection afforded by the barren range which skirts the right bank of the Kan-chou River from its sharp bend to the north of the city, and which further east rises to heights well over 9,000 feet.' But more important even is the fact, already mentioned, that east of the line marked by the Kan-chou River's debouchure from the mountains there commences a submontane belt where cultivation over naturally fertile slopes can be carried on without need of irrigation.
The very position which the Kan-chou district occupies in relation to the rest of this ` passage land ' along the north foot of the Nan-shan must have necessarily led to the creation within it of an important centre for administration and trade. Kan-chou lies just about half-way between Su-chou and Liang-chou, the two areas capable of supporting a larger population which terminate this ` passage land ' on the west and east respectively. To the south-east Kan-chou is directly connected with Hsi-ning, that important Chinese frontier district towards Tibet, by a much-used route which crosses