Chapter 16

Extempore jetty, to build.

TARTAR POLE AND FAGGOT BRIDGE.

We, on one occasion, when encamped on the banks of a large Indian river, were called on to provide for the immediate transport of a battery of field guns, waggons, horses, &c., to the opposite side. Some large native boats were procured, but they, even when empty, drew so much water, that they could not be made to approach within some distance of the shore. We therefore felled two trees, which fortunately stood side by side, letting their crowns fall from the bank, well out into the stream. We soon foraged out three large dug-out canoes, which were concealed among the reeds hard by. These, with our own axe, and those of two stalwart-limber gunners, we split into lengths of uneven plank. Whilst we were doing this, a party had been at work forcing down large heavy branches between the two tree trunks, and on these compactly-bound faggots of brushwood (which a number of natives attached to the expedition prepared close at hand) were rammed and stamped down. Tho boards procured by cutting up the canoes were arranged side by side on this bed, their ends being secured by burden ropes knotted together and hitched over them, as shown atFig. 1, p. 292. We now employed the natives in throwing buckets and bags of earth and sand thickly over and between the planks. Over this extempore jetty—which reached out to the boats, on some of which platforms had been erected—all our battery, consisting of two 12-pounder howitzers, andfour 6-pounder guns, with all their equipment, passed in perfect safety. The work was not commenced until late in the afternoon, and all had crossed long before morning.

Extempore baggage derrick.

It not unfrequently happens that there is greater difficulty in transporting the baggage of an expedition across a river than in getting over the men and animals. This was the case in the following instance. We were exploring the Victoria River, in North Australia, when we came to a branch of one of its tributaries (Jasper Creek) so much swollen that it was unsafe to attempt crossing it with loaded horses. We found, however, a passage to an island, on which stood a couple of tall overhanging gum trees. We had with us several fathoms of Manilla line, about ½in. in diameter, this was passed over a fork of one of the highest and most projecting branches. Mr. Gregory swung himself across, we followed; and while our head stockman, with a fatigue party of five horses, brought the packs to the island, one man lifted the pack that had been bent on to the line as high as possible; another gave an extra pull upon the other part to lift it as clear of the water as possible during its passage, letting go by the run as it swung to the other shore, where one of the party stood ready to catch the pack, while we, making a sharp run with a small line, helped it across, and checked any tendency to swing back again. In this manner we brought over a ton and a half of provisions and stores in between two and three hours; the unloaded horses found a practicable ford a little higher up.

Tree footways.

Sometimes the interlacing of overhanging branches answered our purpose; or we found it possible to fell a tree so that its head might fall on the other shore, or into the water pointing up stream, so that it would drift and jam against the opposite bank.

On another occasion, coming to the Lua, a tributary of the Zambesi, rushing through a narrow place, we went to the edge of the forest, and with a small tomahawk cut down the best tree we could find, and, assisted by three or four Makololo, carried it to the brink, raised it, and let it fall across.

Chain bridges, to construct.

In many of the colonial streams it is necessary to provide the means of passage, for the fords may be inconveniently farapart. In such cases the general expedient is to purchase the chain cables of some wrecked ship, and stretch them across, securing the ends either to stout posts or bars wedged into clefts in the rocks, or to tolerably broad surfaces of timber buried 6ft. or 8ft. in the earth. Of course strong purchases are required to stretch the chains, especially if the distance between the river banks is great; but the buyer would most likely take care also to provide himself, when he obtained the chains, with a pair of large double blocks with iron-hooked straps, and twenty or thirty fathoms of stout rope; so that, when such a tackle is hooked on, and the fall made fast to the trek gear of a span of well-trained oxen, the chain must come or something give way.

Two parts of the chain must be stretched so as to assume perfectly parallel curves, and on these the planks for the roadway are laid, the lashings passing conveniently through the links and preventing any possibility of slipping; other chains or ropes are stretched as hand-rails, and for the supports of these it is a good plan to cut young trees, say 12ft. long, sling them about 4ft. from the top, and fasten them to the chain, so that the upper part will support the rope, while the 8ft. of butt hanging below serves as a counterpoise to keep it upright. This, however, must depend on the height of the bridge; for if the water catches any part of it during the rainy season, there is great danger of the whole being swept away; and it is therefore advisable to make all the fittings as light as is consistent with the safety of passengers, so that in case of extraordinary floods they may be swept off before they communicate strain enough to break the chain—just as the masts of a vessel ought to be of such strength as to be carried away before they capsize the ship. We have seen a bridge built of planks and trestles, very slightly fastened together, but every part was moored by a long line to one or other of the banks. The whole affair would go to pieces when the floods came, and when they subsided the pieces were hauled in, and the bridge reconstructed.

Fly bridges and ferries.

In broader rivers the chain is carried across, and a barge is built with a winch at either end, round the barrels of which a turn of the chain is taken; the waggon about to cross is drawn upon the platform by two or more of its own oxen, thewinches are hove round, and the oxen draw the waggon up the other shore, without even having been unyoked during the passage.

FLYING FERRIES.

In strong rapid streams an anchor and cable is laid high up the stream, and the lower end terminates in a bridle. The boat is alike at either end, and when about to leave the shore the end of the bridle which happens to be forward is gathered in, while the after one is somewhat slackened. The boat shoots over to the other shore, and is kept there by the force of the stream, so long as the bridle nearest the bank keeps her head more up than the farther one allows her stem to be. To bring her back again, haul in that which is farthest from the shore; slack off the other, and she will recross the river as if of her own volition.

The same may be effected by means of the rudder. Have a short mast, to which the cable is attached just high enough to clear the heads of passengers, &c., and about one-fourth or one-third from the bows. Then, if the boat be lying on the right bank of the river, her port side will be to the shore; and as long as the helm is to starboard, or away from the shore, the rudder will incline the boat’s head inward, and the force of the stream will keep her there. But put the helm aport, her head will fall off, she will shoot over to the left bank, and remain there. In fact, this flying bridge, or ferry—for it partakes of the nature of both—acts in the water on the very same principle that a kite does in the air. The line being made fast, not to the stemof the boat, but to a point about one-third aft, would allow her to ride straight on end with the stream only so long as by careful steering her head was kept exactly to it; but the moment an inclination is made, by putting the helm, say “aport,” the boat’s head inclines to starboard; she receives the stream upon her port side, which should make an angle of about 22° with the line of the current, and she at once sheers to starboard or to the left bank—remembering always that, in speaking of a river, the observer is supposed to face down stream, and the banks are named as they are on his right or left hand. A wire rope ferry of this kind is stretched across the united rivers “Moola Moola” and “Moola Moota,” near Poona. We have crossed by it often, and found it to answer admirably.

WIRE ROPE FERRY.

Sometimes it may be of importance to bridge a ravine, which, though not impassable for an active man, is difficult for average passengers. The first requisite is to get a line across. If the nearest bank is a precipice a man may be lowered down with a rope, and he may then climb the opposite cliff, taking the rope with him; but if the farthest bank is precipitous also the case is more difficult, as the rope will not help him to ascend. Perhaps by walking up or down the bed of the gorge while his friends above follow him with the rope, he may find a practicable route; or another party may be sent many miles up or down to find a crossing, and, by lowering another rope, haul him up with the first still fast.

Line slings and lobsticks.

If neither of these plans is possible, a stone or leaden weight may be slung over with a small line, much as sailors heave the lead. We usually employ for this purpose a contrivance known among hunters as a “squailer,” or “lobstick.”

LOBSTICKS.

There are several ways of making a lobstick; the best, perhaps, being those represented by Figs. 2 and 3 in the engraving below. An oval ball of lead, with a hole through the centre, and about 6oz. in weight, is prepared. A strong, tough, and slightly flexible stick is now fitted to the hole in the lead, in which it is held by a wedge driven into its cleft end. A long light line, either twine or fishing line, is now coiled evenly down on the bank, one end is firmly knotted to the extremity of the handle of the lobstick, and the other to a peg driven into the ground. The end of the stick where the twine is made fast is now held lightly in the hand with the ball downwards; two or three rapid and powerful turns round the head are now taken in such a way as to cause the stick to bend. It is then hurled, at a good elevation, across the stream or gorge, where a man who has previously crossed is waiting for it. The string once across, a rope attached to it follows. No one unacquainted with the use of these implements would believe that they could be thrown to the incredible distances which they at times reach. Fig. 1 is an extempore lobstick, made by splitting the handle, inserting a pebble or suitable stone, and then lashing the divided stick fast with twine. A line may be sent over by an arrow or rocket, taking care that the attachment is made with wire or raw hide, so that it may not be burned through. Or, if the ravine be wide, it may be carried over by a kite, and if materials are at hand this kite may be made large enough to carry a man also. There is no fear of the kite line breaking. If there is rope enough to make a bridge, there must be enough to fly a kite strong enough to carry a man.

Makeshift fastenings.

POLE CHAINS.

The communication being effected by any of these means, the next thing is to haul ropes of increasing weight and power across till they are strong enough to haul over the actual cables, and these may be made of various indigenous materials: the bark of the mimosa, of the baobab, and other trees; the fibre of yucca or aloe leaves, or, still better, of those of thePhormium tenax; bush vines, bind weed, or creeping plants; rattans, grass, or strips of palm leaf, may be twisted into ropes; or poles of any straight wood, of nearly even thickness, may be cut and used as links of a chain, by being strongly, yet somewhat loosely, attached to each other by shorter links of rope. Sometimes, if a hole be cut in the butt of one tree, the young branches of the other will be found pliant enough to pass through it, and weave around the stem and the few forks that may be left on it for that purpose.

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 convexside 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 shearsto rise as the others are lowered, keeping a check upon them all the while, until the first are laid fairly across.

If the gulf is wide, this operation might be carried on from both sides till the shears meet, and could be secured together in the middle, as in our illustration; and the roadway could then be constructed between them.

BRIDGE SHEARS.

Guano stages at Ichaboe

When vessels first went to the island of Ichaboe for guano, it was customary to require every new comer to bring two or three stout spars for the purpose of extending the landing jetty; and as each had the benefit of the spars left by former vessels, so each was expected to leave her own for the use of those who followed.

Owing to the irregularity of the rocky bottom, thickly covered with seaweed, the depth of water, and the distance from shore at which the surf began to break, all the ordinary methods of constructing a jetty were impracticable, especially when the object of each captain was to load his vessel as quickly and easily as possible, and to get away without expending the labour of his crew on works more than sufficient for his own service. Besides this, even had holes been bored, piles driven, and a staging laid down upon them, the platform, if permanently spiked down, would inevitably have been torn up by the surf in even a moderate gale; or, if loosely laid, would have been liable to such constant derangement as to be practically useless. It was necessary, therefore, that the base, while strong.enough to support the traffic, should present little or no surface for the waves to act upon, and that the roadway should be so elevated that breakers could not touch it. Even under these conditions, it was found that the first structures were washed away, and other forms had to be adopted; these could only be built on the north and east sides of the island; they were not less than 200ft. or 300ft. in length, and seldom or never in a straight line.

A heavy bower anchor, sometimes weighted by several lengths of chain frapped round it, was laid down well outside the surf, with one or two fifteen fathom lengths of chain, and to the end of this a stout hawser was bent on and carried to the shore, passing over and lashed to the intersection of a pair of stout poles set up as shears, and with its shore end leading to another anchor or secure fastening, to which, when the structure was completed, it could be tightly set up by means of tackles.

The first pair of shears having been erected, it was comparatively easy to erect others, and often as many as a dozen or sixteen pairs were fixed, the hawser passing over and serving as a ridge rope to them all. At about 12ft. above high water smaller spars were lashed fore and aft, so as to connect all the shear legs on either side through the whole length of the jetty, and others were laid across and well secured by cleats and lashings between each pair of legs, with some at shorter intervals, on which the roadway was constructed of planks and spars, sometimes nailed, but more generally securely lashed. At the end of this staging was a small platform, slung by tackles to the outermost pair of shears, and capable of being raised or lowered, so that boats might lie alongside it either at high or low water.

GUANO STAGE AND FLYING RAILWAY AT ICHABOE.

The flying railway.

Other vessels, not so well provided with spars as to entitle them to share in the accommodation of these stages, adopted a kind of flying railway, such as is used on the rocky coast of the Cape Verdes for the shipment of salt. A stout spar, 40ft. or 50ft. long, or sometimes, if the vessel was totally unprovided, her own mainboom was taken ashore. Smaller spars were set up as shears, and by these the large one was erected, and stayed in a perpendicular position as a derrick. The heaviest bower anchor, with several fathoms of chain, was laid outside the surf, inthirty or forty fathoms of water. A stout hawser was bent on to the end of the chain, carried to the derrick head, and hitched round it or otherwise secured; and the shore end was extended inland toward another anchor, to which it was hauled taut by a powerful tackle. Another tackle served to raise the guano bags to the derrick head, and on the hawser travelled a large snatch or natch block (so called because one of its sides is notched to admit any part of a line, the end of which cannot conveniently be reeved through). A man, seated on a kind of cross-tree, would pass the hook of the travelling block into the slings of the bags when they were hoisted, and would detach the hook of the tackle, and the bags were eased down to the boat lying out, where the hawser nearly reached the sea by a stout line passing through a single block at the derrick head. Generally, the travelling block alone had to be brought back; but if provisions or other stores were to be landed, they were hooked on before it returned. Passengers would be landed or embarked in the same manner; sometimes in a stout basket, or in a cask cut into the fashion of an arm-chair; but more generally, in disdain of such luxuries, in the loops of a double bowline—the bolder spirits glorying in being let go by the run, and gliding down the hawser just as the Russians do in their sledges on artificial ice hills.

It will often happen that in the erection of some makeshiftcontrivance, or the laying out of a ground plan for future operations, some rough and ready mode of levelling will be needed.

Levelling.

The Dutch African farmers use a very simple and effective level in laying out water furrows for the irrigation of their farms, and, when it is understood that even on very favourable ground these furrows are often two miles long, it will be seen that some little engineering is required. They take a table, the longer the better, and having tested its surface by the eye, and by lines stretched across, they place on each end a large basin filled to the brim with water. When these are perfectly full without overflowing, the sight is taken over them at a staff set up upon the next station, and the height of the mark on this, less the height of the table and basin, gives the difference of level.

SOUTH-AFRICAN LEVELLING TABLE.

We had a tube of tin 4ft. long and 1in. diameter, with two pieces of glass tube bent upward, passing through corks in either end, so that, by using water coloured with charcoal or mud, we could at once observe the true level. A long bamboo or reed closed at the ends, but open in all its intermediate length, will do just as well, and there is no necessity that it should be straight. Smaller pieces of reed, 3in. or 4in. long, should be set up in each end, and the bore of these must be large enough to allow the water to flow freely to its natural level. The top of these may be notched for sights like those of a rifle, or sliding sights may be fitted on the side of them. This instrument may beused for taking vertical angles by fixing the eyesight upon a pivot, marking the place of the foresight on the staff, when the level has been taken; then pouring away the water, sighting the top of the object, marking the elevation upon the staff, and then either drawing the obtained angle on paper, or taking the difference between the base and perpendicular, and then working out the result by the rule of three.

Deodar bridges.

DEODAR BEAM BRIDGE.

One of the bridges over the Sutlej is formed of lengthy deodar cedar beams, supported at either end by piers formed of very strong timbers wedged for half their length in the solid rock, the next timbers overlapping those on which they rest by 2ft. or 3ft., these in turn being overlapped by others, till the space between is so much diminished, that it can be spanned by the long deodar beams.

INDIAN ROPE BRIDGE.

Rope bridges.

The Jhula, or rope bridge, has a kind of seat slung to it, capable of being hauled to and fro by lines to either bank, and the live stock, aswell as the baggage of passengers, is secured to this and sent across. Other bridges are made of ropes of birch twigs, two of which are stretched across from rude piers upon the banks, and from these, hang cradle like, a continuous hurdle of the same frail material serving as a footway, and attached to the ropes by a sort of open basket work, a couple of smaller ropes stretched beneath helping to support the roadway. This, apparently, by its own weight and the unequal stretching of its parts, soon gets out of order, and the passage is a somewhat hazardous feat (see illustration,p. 335).

Deris, to make.

Sometimes the rivers are crossed on deris, or skins of bullocks, which are thus prepared: One cut is made along one hind leg, the skin is then turned forward and stripped off uncut, except at the hocks and knees; it is buried a few days to facilitate the removal of the hair; it is then again turned inside out, and the openings of the eyes, mouth, &c., sewn up; it is then turned back again, and the incision stitched together with thongs of raw hide; the open ends of the limbs are tied, except one, which is left as a tube to inflate the skin; the thin tar of the deodar, or other pines, is poured in and shaken about till the flesh side is well charged with it, and the outside is tanned with an infusion of pomegranate husks.

A double cord is fastened round the inflated skin, across which the waterman lies on his chest, holding the string with his left hand and working a short paddle with the right, assisting himself also with his feet. The passenger, with as much baggage as he can carry, sits astride on the ferryman’s back, with his knees on the skin. When heavy goods are to be carried, two skins are brought together, each man laying hold of a projecting leg of the other skin, and a frame—often of a “charpai,” or Indian bedstead—is laid upon their backs to receive the load. Horses or mules are made to swim, the ferryman leading them by the halter. The appearance of the inflated skin, when carried by the waterman, is most ludicrous (seep. 333); but when the air is let out it packs very conveniently. It is exceedingly serviceable, costs about 3s., and weighs about 16lb.

Rafter, plank, and slab bridges.

PLANK ARCH.

Very neat and effective bridges may be made on the rafter principle, which our engraving atp. 303will sufficiently illustrate. The roadway, either horizontal,as in Fig. 1, or with more or less rise in the centre, as in Fig. 3, being supported by the king-posts, a tolerably broad river may be spanned by a bridge supported on latticed-worked sides, like a number of X’s set up without intervening spaces; but this would require skilled workmanship and secure fastening. Arches of great strength may be made of thin planks laid one upon another; a dozen inch planks would thus give an arched beam 1ft. in thickness, and when properly clamped, or bound together, exceedingly strong. This beam may be easily lengthened, no joining or scarping of the individual planks is required, their ends may simply butt against each other; but care must be taken that no two joints come even nearly together, or much of the strength will be thrown away.

CHINESE SLAB AND TRESTLE BRIDGE.

Many Chinese bridges are constructed with slabs of stone, set up much in the manner of those at Stonehenge. A number of bridges of this description, formed entirely of granite, are to be seen on the Cornish moors.

An Indian army was once sent to act against an enemy accustomed to a colder clime. A broad river checked the advance of the Indians, who had to remain day after day shivering from cold which their enemies bore with impunity; but their leader observed that ice was forming on the river, and, though the strong current kept the centre clear, he found a place some miles below the hostile camp where it had nearly united. By pushing forward poles and faggots into the water he made a nucleus on which fresh ice was formed, and before morning he had sufficiently bridged the river to allow of the passage of a few men who held their position till the rest could cross.

Hints on fording rivers.

In fording deep and rapid streams, the tendency of the body to float greatly diminishes the power to resist the force of the current.We have seen a short and compactly built man, struggling against this difficulty, when a couple of tall aborigines came to his assistance, and with mistaken zeal put their hands under his arms to hold him up, till he explained that he wanted them rather to press upon his shoulders and keep him down. A detachment of our troops found themselves before a ford where the stream was deep and strong, and while they hesitated, the tall guide picked up a heavy stone, placed it on his head, and walked safely through. It is to be remembered, however, that the ford which is safe for the first man is not always so for the last. An ancient general attempted the passage of a river, but the trampling of the men and horses loosened the sand, the stream swept it away, reinforcements were unable to come up, the advance was beaten, and in attempting to recross the river, numbers were drowned, owing to the increase in the depth of water.

In most countries native paths will lead to the practicable fords, and very frequently villages will be established near them, so that information and guides may generally be obtained. In the Cape colony, people who live near the drifts or fords of large rivers frequently keep spans or teams of powerful oxen for the sole purpose of drawing the waggons of travellers across, and these are generally led by some stout young fellow on a horse that is also well accustomed to the locality. It will often happen in the course of exploration that the traveller will have to find the shallow places for himself. Reefs, or edges of strata, running across the river are, of course, obvious enough, but to find moderate shallows in a river of more even depth is not quite so easy; the best way, therefore, is to follow the windings, bearing in mind generally it is better to seek up the river than down where fresh tributaries increase it. In all the hollows where the stream impinges strongly upon the banks they are generally very steep, with considerable depth of water, while the points will be found to slope downward with shoals extending from them, and there is generally an eddy or return current on the upper side; therefore, if a point can be found, with another somewhat below it on the other side, a ford may reasonably be looked for, especially if the width between the points seems greater than usual. A ford seldom leadsstraight across a river, and there is little use in looking for one in a hollow or under a steep bank.

PORTABLE INCLINES USED IN ABYSSINIA.

Abyssinian mule platforms.

Mr. Percival, who has travelled much in Abyssinia, tells us that he used what he calls portable inclines to facilitate the passage of his long and heavily-laden mule trains over difficult places, especially such as the perpendicular edges of stratified rock 2ft. or 3ft. in thickness, which to laden mules would be as impassable as precipices of a thousand times the height. To obviate this difficulty, he employed one or more mules in carrying roughly-made platforms of stout poles about 10ft. long, with others lashed across them, ladder fashion, so as to present a surface of about 10ft. by 2ft. It would be the duty of the drivers of these mules to have, at least, one of them well to the front in anticipation of any difficulty; the platform would then be laid down, the train would walk over it and pass on, leaving it in the rear to be loaded up again and brought on, while one of the other platform mules would pass to the front in order to be ready for the next difficulty.

The length of these would depend on the height of ledge of rock to be mounted. Suppose the strata were 3ft. in thickness, then a platform of 4ft. 6in. would present a surface lying at an angle of 45°, while one of 7ft. 6in. would lie at 22°; this, for short distances, would not be at all a difficult incline either to descend or to climb, and platformsof 10ft. would give plenty of spare end to rest on the supporting edges, and would not be very inconvenient in carriage. Mr. Percival says he has made them of wattled or hurdle work from 12ft. or 15ft. up to 24ft. in length, and yet so light that one mule has carried two of them; and in following what are called the torrent roads, at the bottom of deep ravines, these would come into requisition at every few hundred yards.

It was in such ravines as these that most disastrous events were anticipated by travellers who knew the difficulties of the country, without being at the same time aware of the skill and resources of our military engineers.

In native warfare an army might be watched into a place from which escape is hopeless, and in the dry season the grass would be then fired at the entrance and the exit; or in the rains, some small river might be partially dammed up so as to accumulate a quantity of water, which being let loose at the proper moment by the dragging out of a pole that serves as a trigger to let go the rest of the impediments, would sweep down upon and overwhelm the helpless enemy.

Natural bridges.

Leaping poles.Makeshift ladders.MINERS’ SWING AND LADDER.INDIAN ESCAPE POLE.INDIAN SCALING LADDER.ROPE AND CHAIN LADDERS.

Leaping poles.

Makeshift ladders.

MINERS’ SWING AND LADDER.

INDIAN ESCAPE POLE.

INDIAN SCALING LADDER.

ROPE AND CHAIN LADDERS.

Besides the modes of crossing rivers or ravines before described, there are various methods of passing over comparatively narrow impediments to the onward journey. A chance tree, storm felled across the stream or gully, not unfrequently affords the requisite footway without the expenditure of labour. There are, however, localities in which old hollow logs, cast in this manner across water, are to be looked on with some degree of suspicion, as the following incident of travel will serve to show: An old friend of ours chanced one day to arrive much fatigued at the brink of a tropical stream, which had one of these natural bridges thrown by some storm across it. Before passing over, he lit his fire, cooked his food, and indulged in a quiet smoke; happening to cast his eye along the fallen tree trunk, he perceived something of rather sinister appearance, in slow motion, on its surface. On looking more closely, he saw a huge python, half in and half out of a hole in the log, apparently enjoying the rays of the mid-day sun. The bark of the tree near to the bank, on which our friend was sitting, was worn quite smooth by the passage of numerous animals, and there is no doubt that this formidable toll collector hadlong enjoyed the monopoly of his tree bridge. Our friend selected another crossing place less carefully guarded. Small streams, or the narrow channels of swamps, may be easily and expeditiously crossed by the aid of the leaping pole.Leaping poles.Tall bamboos or tough, straight, well-grown poles are suitable for the purpose.MINERS’ SWING AND LADDER.In soft fen ground, it is a good plan to shoe the bottom of the pole with a piece of flat, strong wood, formed somewhat after the manner of a half ball, with a hole in the middle for the reception of the end of the pole. In exploring the cliffs at the edges of ravines, the metal seeker not unfrequently swings himself from ledge to ledge by the aid of a rope attached above, as shown in the accompanying engraving. The cliff climbers, who search for the eggs of sea-fowl, roam about at times in much the same manner. In descending from points of danger, where a leap for life affords the only hope of escape, advantage may be taken of the contrivance which was used by the rebels at Kotah, in India, during the mutiny.INDIAN ESCAPE POLE.They, on being pushed hard by our troops, who had gained possession to the approaches to their fortified works within the town, bolted like rabbits in a warren, and made for an embrasure, or rather casemate, in one of the bastions of the outer wall; from this they thrust out a strong,but flexible bamboo pole, from the end of which a rope depended. The inner end of the bamboo was secured by heavy weights being placed on it. The fugitives worked their way out by clinging under the pole, until they in turn reached the rope at the end, when they slid down to the end, and then dropped off into the dry ditch. Judging from the immense height of the bastion, and the rocky nature of the ground, we should have had but faint hopes of escape with life; but there is little doubt that many who braved the peril of the fall escaped more or less injured.Makeshift ladders.We had no means at hand of measuring the bamboo, but should judge it roughly at 40ft.INDIAN SCALING LADDER.The illustration on p. 347 will serve to show the manner in which it was made use of. Not far from the bastion just referred to, we found a number of Indian scaling ladders. They were much in appearance like large bamboo hurdles. The canes composing them were bound at their intersections with strips of twisted cane. They were, for their size, remarkably light; and the nature of the material of which they were constructed, and the way in which they were put together, made them immensely strong. A number of men abreast might have ascended them easily. There are many forms of makeshift ladders, amongst which, perhaps, the following are the most noteworthy.ROPE AND CHAIN LADDERS.The ordinary rope ladder is too well known to need more than a passing comment. The rope and batten ladder is perhaps not quite so well known, but is far more easy to mount and dismount; its form is shown at A in the accompanying illustration. Two strong chains, and a set of suitable sized bars, form a very useful kind of ladder, much in use among miners; its mode of arrangement is shown at B in the annexed illustration. In South America and some other countries, the notched log ladder is much used both in mining and surface operations. It is, as its name implies, a log notched deeply to receive the feet and hands of the climbers. Another form of log ladder is made by boring a row of auger holes at equal distances, say 2ft. apart, and then driving long stout treenails through them, so that each end of the treenail may project beyond the side of the log, for a hand and foot hold. Long forked branches may have their lateral shoots cut off at convenient distances apart, so as to form a footway of short prongs. A row of spikes or treenails may be driven into the side of a cliff, a wall, or the trunk of a tree to climb up by. The natives of many wild countries adopt this method, about which we shall have more to say when the subject of tree-climbing is under consideration.

Landing derrick.

PEG, BRANCH, AND LOG LADDERS.

LANDING BY SWINGING DERRICK.

In some parts of the world, the operation of landing from a boat, or embarking from the quays or jetties built out into the sea, is rendered both difficult and dangerous by the great range imparted to the boat by the roll of the swell, which in the Eastern seas is at times very great. In such situations, it is a good plan to have a stout post set in the masonry, or in a hole made in the rock, and to the top of this post a swivel crutch, which holds the trunnions of a long projecting arm, like that of an Egyptian well lever, to the small end of which a rope and cross-bar are securely fastened. To the short, heavy end, several more ropes are attached, by which when the person to be landed has either grasped the cross-bar, or seated himself on it, the contrivance is at once raised aloft, and turned steadily but rapidly inward, when by easing off, the man is allowed to drop easily to his feet on solid ground. There used to besuch a contrivance as this at St. Helena, by the aid of which we have often landed. The illustration onp. 349will serve to show how the apparatus is managed and constructed.

A barrel, stoutly lashed with rope, fitted with a seat, and cut away at the side, so as to admit of the traveller sitting in it, as in a chair, is used for ladies or invalids, who are slung in it at the end of the arm, and hauled in as above described.

Bridges of boats.

Sometimes it is necessary to construct bridges of boats; and these are often works of great magnitude, requiring a considerable amount of material, especially when an army with artillery and baggage waggons has to cross. Whether large or small, the method of proceeding must be nearly the same. First, a number of stout beams must be collected, sufficient to make a double line across the river, with their ends overlapping each other by more than the breadth of the boats that are to support them. The boats should be brought to the shore and moored a little above the site of the intended bridge. If anchors are procurable, they should be laid at regular intervals across the river; a buoy should be attached to the end of each cable, and a small line should lead from the farthest to each nearer one in succession, till they are all connected with the shore. A substantial frame of beams should be constructed at the edge of the bank, and a boat brought alongside it riding by the first cable, and secured by a temporary mooring to the shore. Two beams must be launched across her near the head and stern, and firmly lashed to the thwarts and stringers.

The boat must now be swung out to the full extent of the beams; the second cable must be laid hold of, and the first cast off and hauled to shore for the next boat, which is dropped down stream under the shore end of the beams, which are laid upon her gunwales and made fast there; while two others are pushed from the shore and fastened to her as the first pair were to the first boat. Intermediate beams, if requisite, can be laid, and planking lashed or pinned upon them so as to complete that part of the platform. Then other beams and planking, sufficient for a similar platform, should be brought on board, for the purpose of finishing the bridge when this pair of boats reaches the other shore. The outermost boat should now pick up the third cable,and pass the second to the inner one; while the first cable should be taken by a third boat, which will drop down between the others and the shore, to receive her portion of the platform; and so on in succession until the bridge, completed as it goes on, extends so nearly to the other shore that the loose material carried by the first pair of boats serves to complete the connection.

EXPEDIENTS FOR BOAT BRIDGES.

Anchors may be extemporised from forked branches of trees—the harder and heavier the better. These should have stones or iron lashed to them, in order to give weight. Several forks should be left on the main stem, and pointed to insure their holding. If charred in the fire, so much the better, as their durability and strength are much increased by the process. If there is but one fork, care must be taken so to balance the anchor with the stone below and the cable above, or a stock lashed across, that this fork or arm shall be sure to take the ground. The bridge may be also shored against the stream by branches, with their forks taking the beams, while their lower ends, weighted by stones, rest against the bed of the river. Stones are of no use as anchors, as they lose so much of their specific gravity when immersed; but if a heavy stone can be dropped beyond a cleft in the rock, as in our sketch, it will hold well.

If no anchors or substitutes can be had, the cables may be made fast to a stout tree as far up the stream as possible; and being brought in upon the inner bow of each boat, she will take the stream upon thatside and be forced outward. The rudder, if she has one, will assist in this, but it is not material, as she can be kept at the proper angle by making the foremost beam a little longer than the after one.

If the bridge is constructed so low down the river as to be within the ebb and flow of the tide, anchors are indispensable, and each boat must be moored head and stern, as shown in one of the examples in our illustration; or, if there be but one cable to hold her against the ebb, shores may be set so as to counteract the influence of the flood, unless a great rise and fall, or violent rush at the turn of the tide, should render it unsafe to use them. If boats cannot be had, two or three large casks, placed end to end and firmly lashed to poles laid parallel to their length, may be used at each junction of the beams; or if a number of small ones can be obtained, they may be collected within a triangular frame of poles; but in any case each float must be sufficiently buoyant to keep the bridge at least 3ft. clear of the water, if there is any current; if there is none, the platform may even touch the water, and be partially sustained by it. In our sketch we have omitted all but a small portion of the planking, in order to show more clearly the manner of connecting the framework.

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