CABLE AND TWIG BRIDGE.
Bamboo maybe partially cut away nearly up to a joint, leaving long strips on either side, which being doubled back on themselves form excellent links; or they may be split up and spliced together like the strands of a rope; and, from the great number of very small, long, and pliant branches growing from every joint, bamboo offers great facility for the attachment of other fastenings at every foot of its own length.
Cane and twig roadways.
The cables having been stretched across and securely fastened, the next requisite is the construction of the roadway. If bamboo is the material, the large stems may be cut into lengths of about 5ft., and split into four, giving pieces of, perhaps, from 4in. in width.; these should be laid with the convex side upwards, projecting about 1ft. beyond the cables on each side, and securely lashed to them—the small shoots already mentioned will very materially assist this process. If smaller bamboo is about to be used, it can be split into three or four parts, or put in place without splitting. Small ropes should be provided as hand rails or safety lines, and these must be confined to the sides of the bridge by upright stancheons about 3ft. or 4ft. high, and placed tolerably close together. Twig ropes stretch very unequally in use.
Rattans and creepers are often of very great length, and pieces 100yds. long, and not above 1½in. in thickness, may be disentangled in the forest. These can be utilised in a variety of ways. Sometimes a roadway is made of short pieces of wood suspended at either end from the cables, but in this case the amount of small line required is greater; and, what is of more importance, the safety of the traveller depends at every step on the fastening of the piece he treads on, while in the former case, even if the fastening were insecure, the cable would support his weight. Besides this, in order that they may not swing apart, every piece must be lashed to its neighbour; and it seems more safe and economical to build the roadway on the cables, and stretch lighter ones above them for safety lines.
Bridge shears, to construct.
If the ravine is not very broad, a tree, such as the stem of a tall palm, which will often be 60ft. high, and 1ft. in thickness; or a bamboo, which will be sometimes 80ft. or 90ft., may be raised, and secured by stays and guys in a vertical position; or, still better, two may be lashed together as shear legs and then raised. If the ground is good this need not be done at the very edge of the cliff, for when once the shears are nearly upright, smooth planks may be put under the butts of the spars, and they may be pushed or hauled in any direction.
If men can find a passage to the other side, and carry over some of the stays and guys there, the work will be much facilitated. If not, make another pair of shears exactly like the first, and lay them horizontally on the ground, with their butts resting against and fastened to those of the upright ones; let the stays come to the head of these, slack them a little till the uprights incline forward 20° or 30° over the gulf, then keep all fast, and allow the horizontal shears to rise as the others are lowered, keeping a check upon them all the while, until the first are laid fairly across.