Up the Mekong Valley 45 
big slabs of shale, that the very thinnest of wheat crops 
comes up, and a much larger area is under cultivation than 
would seem necessary from the size of the population. 
Tsu-kou itself boasts scarcely a dozen huts, and scattered 
up the cultivated slopes of the barrier range are other small 
villages. Before 1905 the Catholic mission was established 
in Tsu-kou, but after the burning and sacking of the village 
by the Tibetans, who rose against the Chinese all along 
the border from Batang southwards, it was rebuilt at 
Tsu-chung which is now the more important village, 
boasting perhaps a score of families, besides a garrison 
of thirty Chinese soldiers. The charred walls of the 
mission house at Tsu-kou still stand to mark the site, and 
close by are the graves of the two French priests who 
perished in the disaster. 
The barrier range above the river has been blocked 
out from the main range by the torrents which flow diago- 
nally towards the Mekong in the upper part of their 
course, thus cutting out a wall of rock in front of them, 
through which they are eventually compelled to saw a 
deep gorge to the river, though a few of them plunge 
over the precipice. 
The tortuous courses of these streams, with the con- 
sequent formation of barrier ranges, seems to be largely 
due to an unequal distribution of rainfall in the mountains 
and in the valley aided by the general N. and S. dip of the 
strata. Here there is a very heavy rainfall on the Mekong- 
Salween watershed throughout the summer, and a moderate 
one in the valley; but as we go further north there is an 
equally heavy rainfall on the divide, while only a negligible 
quantity of rain falls in the semi-desert valley ; and immense 
spurs buttress the watershed from river to crest, with no 
sign of any barrier range. The same structures occur on the 
Salween on a still larger scale in the rainy and arid regions 
respectively. 
After four days in camp with my three men, the local 
Tussu requested us to move into one or other of the villages, 
as he was afraid that we might be plundered in the 
night by mountain robbers. Meanwhile I had made friends 
with the two Catholic priests at Tsu-chung, Peres Mombeig 
and Lesguergues, who visited me in camp and several 
