Up the Mekong Valley AI 
are cut transversely through the convex upper face of the 
semi-cylinder, near each end, and beneath the handles so 
blocked out are threaded leather thongs. 
If the gradient of the rope is small, so also is the 
friction of the slider, and the weight of the rope causing 
it to sag towards the far end, the rope dips more rapidly 
to begin with than it would if it were rigid; consequently 
the impetus gained at the start is sufficient to carry one 
across the river. On the other hand the sag, still further 
emphasized by a person’s weight, causes the extreme end of 
the rope to slope up towards the landing stage, so that the 
person crossing usually has to pull himself up a few yards at 
the end. 
It will readily be seen that, since this is a single-way 
rope bridge, there must necessarily be two of them at each 
crossing, one each way ; moreover, that the method is only 
practicable where the banks are steep and the river com- 
paratively narrow. Of the dozens of single-way rope 
bridges I saw, I do not suppose one of them spans more 
than thirty yards of water. For this reason they are not 
found on the Yang-tze, though they occur a long way east 
of it, on the Yalung river. 
On the other hand, given a narrow river and steep 
cliffs, there is no limit to the height at which the rope may 
be suspended above the river, and the lowest point varies 
from a few feet above the water at winter level—such 
ropes being partly under water during the summer rise, 
and therefore impassable—to as much as eighty or a 
hundred feet above, as is the case with the rope at 
Samba-dhuka, also over the Mekong, which spans an 
extraordinary gorge measuring about twenty yards from 
cliff to cliff. Alarming as these greatly elevated ropes 
appear, however, it would really make very little difference 
whether one fell into the Mekong from a height of one 
hundred feet or a height of five feet. 
As far as the traveller's own feelings are concerned 
the crossing of the bridges seems to be accomplished with 
the speed of an express train, but Mr Edgar, of Batang, 
who carefully timed several journeys, obtained an average 
speed of only ten miles an hour, though animals may 
possibly travel twice as fast. Of course different ropes 
