Up the Mekong Valley 39 
thirty feet high ; sometimes we plunged into a deep lime- 
stone gorge, its cliffs festooned with ferns and orchids, our 
caravan climbing up by rough stone steps which zigzagged 
backwards and forwards till we were out of ear-shot of the 
rapids in the river below ; sometimes the path was broken 
altogether by a scree-shoot, which, dangerous as it looked, 
the mules walked across very calmly, though sending rocks 
grinding and sliding down through the trees into the river. 
In one gorge through which we passed, large pot-holes 
were visible across the river between winter and summer 
water marks and yet others still higher up, forming a con- 
spicuous feature of the otherwise smooth bare cliffs which 
dipped sheer into the river; but on the left or shaded bank 
dense vegetation prevailed wherever tree, shrub, or rock- 
plant could secure a foothold. The further north we went, 
the more rich and varied became the vegetation of the 
rainy belt, though the paucity of forest trees, except deep 
down in the gullies, was always conspicuous. 
Shales and slates, dipping at very high angles, and 
often vertical, alternated with limestone, through which 
the river had cut its way straight downwards; but at one 
spot, where an enormous rapid had been formed, huge 
boulders of a dark green volcanic rock, like lava, with 
large included fragments, lined the shore and were piled in 
confusion below cliffs of slate. 
It is at sunset that the charm of this wonderful valley 
is displayed at its best, for the sun having dropped out of 
sight behind the western range still sends shafts of coloured 
light pulsing down the valley, rose, turquoise, and pale 
green slowly chasing each other across the sky till darkness 
sets in and the stars sparkle gloriously. It is long after 
dawn when the sleeping valley wakens to floods of sunlight 
again, and the peaks which stand sentinel over it, blotting 
out the views to north and south, lose the ghastly grey 
pallor of dimly-lit snow. 
On the third day I noticed that one of the muleteers, a 
Lissu from Hsiao-wei-hsi, was limping badly, and in the 
evening I looked at his foot, which had been severely cut 
on a rock; for most of these men go about bare-footed. 
The sole was protected by a layer of tough horny skin 
three-eighths of an inch thick, grimed with dirt, and so 
