EXTEMPORE BRIDGES AND MAKESHIFTS FOR CROSSING
RIVERS OR RAVINES.
The solitary traveller in a wild country will be very rarely compelled
to construct his own bridge, for, as a general rule, he will only have
to pass once, or at most to return by the same route. The labour of
making a bridge would be greater, and more time would be lost, than by
seeking for a practicable passage at some distant point, or, in case a
river was the impediment, forming a float of some kind.
{Swamp roads, to make.}
There are, however, occasions when there is no alternative but
bridge-making, as when exploring expeditions, accompanied by pack
animals, or a field force on the march, have rivers, swamps, ravines,
or, perchance, rotten ice, to pass over. Where there is not water
enough to float a canoe, but where there is sufficient to cause the
formation of deep pools and dangerous mire, over which few animals
used for the conveyance of baggage could pass without the aid of some
artificial footway, narrow deep channels may be very often rendered
comparatively easy to cross by filling them up with bundles of
brushwood or marsh reeds. We were constantly in the habit, when engaged
in making forced marches through Central India, of making use of the
stalks of the recently cut juhari for this purpose. Unsafe ice can be
rendered firm and secure by strewing a thick layer of reeds over it,
and then throwing water enough to cause the whole to freeze into a
compact mass.
Before, however, proceeding to describe the various modes usually
had recourse to for rendering trees available for bridging purposes,
it will be well to give a few plain and practical directions for
ascertaining the width of rivers, ravines, and the arms of swamps,
without the aid of scientific instruments, and also for finding, by
makeshift modes, the altitude of trees.
TO FIND THE WIDTH OF A RIVER WITHOUT INSTRUMENTS.
Fig. 1. If you have a pocket compass, and the river runs, say east and
west, and you are on the south side, choose a well-defined tree, A, or
other object on the opposite shore, and bring it to bear north of you;
mark your position by putting in a stake or peg, B, turn to one side,
say the left, and walk westward till A bears north-east, which will be
the case at C; then C B will be exactly equal to B A, or the breadth of
the river, because from the point C, A will bear north-east, and B will
bear east, subtending an angle of 45°, and as the line C B is east, and
B A is north, they subtend an angle of 90°, or a right angle, and must
be of equal length; the triangle you have formed being the half of a
square, divided by a diagonal line from corner to corner.
[Illustration: FIG. 1]
If you have room repeat this by walking east till A bears north-west
from D; and if the first operation has been correctly performed, the
second will confirm it; or if the first be in error, it is likely that
the second will be exactly as much in error the opposite way, and the
mean of the two observations will be approximately correct.
[Illustration: FIG. 2]
Fig. 2. If you have not a compass, choose A as before, set in a
stake at B, and prolong the line to C; then on this line erect a
perpendicular by looping a cord on the stake at C, and with a sharpened
peg held at the other end of it drawing the arc, D E; then, making D
and E equidistant from B, draw through these three points the line D B
E F; on this line retire toward F till A and B form an angle of 45°,
which may be measured either by folding a square of paper diagonally,
or by pegging out a piece of string divided into two lengths of 24in.
and one of 32in. See that the longest or diagonal side bears truly
upon A, and one of the shorter sides on B, which will take place at the
point F, then F B will be equal to B A, or the breadth of the river.
Repeat this also if the ground allows, on the opposite side G, and take
the mean of the two observations.
The correctness of all these observations may be greatly increased by
resting your rifle on each successive point, and carefully sighting all
the lines with it.
[Illustration: FIG. 3]
Fig. 3. Another excellent and simple plan is--choose A; set in B; from
B erect the perpendicular B C, C D, divided equally at C; from D erect
the perpendicular D E; retire along it till the stake C bears truly
upon A, which will be at F, then F D will equal B A.
[Illustration: FIG. 4]
Fig. 4. If the river bank is so curved that you cannot draw B C D at
right angles, you have two alternatives. If there is plenty of room
retire as far as you please from the bank before planting the stake B,
and deduct from the result the distance you retire from the bank. Or,
if there is not room, you may draw B C D, as in Fig. 4, diagonally,
and contrive to keep D E as nearly parallel to A B as you can; but
any defect in parallelism will greatly affect the correctness of your
measurement, as will be evident from the dotted line G.
[Illustration: FIG. 5]
Fig. 5. If the river is wide, choose A as before; set in B, and retire
any measured distance, say 6yds., to C; then from B and C erect
perpendiculars of equal length, and draw the square B C, D E; test it
by stretching a cord from corner to corner; then, prolonging the line C
E, bring the stake D in one with A, and produce the line A D till it
intersects C E at F; then divide F E into six parts, measure as many of
them as you can on the line E D, and you will find as many of them as
there are yards on the line B A; therefore, in the present instance,
11yds. will be the breadth of the river, and one may be deducted
because the marks are not close to the edge of the banks; or say, as E
F is to E D so is B D to B A.
Fig. 6. To erect a perpendicular on a given point on any line,
measure equal distances on either side; set in pegs, loop a cord on
them alternately, and strike two arcs, their intersection will be
perpendicular to the given point. To cross the end of a line by another
at right angles, set a peg some distance back, loop a cord on it, and
strike an arc. Measure equal distances from the end of your given line
to the arc, then a line drawn through the three points will be at right
angles to the first.
[Illustration: FIG. 6]
A scale of equal parts may be made by folding a slip of paper in half,
then folding each part in half, and so subdividing it as much as you
wish, but do not fold it in half, and then double the two parts to get
the quarters at one operation, and then double the four parts to get
the eighths, or you will find them come out very unequally.
A measuring tape may be made by taking a narrow white tape, say 1/4in.,
and winding it on a slip of card barely an inch wide, just so little
spirally that each turn may not half cover the preceding one, then
carefully blacken the edges, and, when you unwind the tape, mark every
twelfth inch with figures to denote feet, and every sixth with an extra
line.
A square is made by taking a sheet of paper, folding the corner down so
that the edge of the end coincides with the edge of the side, and then
cutting off the superfluous length, each corner of the square is an
angle of 90°, _i. e._, a right angle or a quarter of the compass, say
from north to east. The diagonal fold makes at each corner an angle of
45°, or four points of the compass, say from north to north-east; fold
this again, and it will give 22-1/2°, or two points of the compass,
from north to north-north-east, and this may again be subdivided if
needful.
We have often tried the breadth of rivers by firing a rifle ball at
some well-defined mark on the other side, with the sight adjusted to
100yds. or more, according to the estimated distance, and noticing
whether the ball reached beyond or fell short of the mark. The habit
of doing this very greatly corrects and assists the eye in forming
estimates of distance. A good stone thrower ought to know the range he
can make with pebbles of different sizes. If a native is near buy one
of his least valued arrows or spears, and get him to throw it across,
and then ask him to throw a similar one on ground where you can recover
it and measure the distance, but never ask a savage to throw away
weapons of the chase for nothing. In calm weather, we have fired a
rifle ball, with its utmost range, on the surface of a lake, and have
counted seconds from the time we saw the splash till we heard the sound
of its fall. Sound travels 1142ft. in a second, or about a statute
mile in 4-3/4 seconds, or a geographical mile--or rather one minute of
latitude, or of longitude _on the equator_--in 5-3/4 seconds.
TO FIND, WITHOUT INSTRUMENTS, THE HEIGHT OF A TREE OR OTHER OBJECT,
WHOSE BASE IS ACCESSIBLE.
Fig. 1. Fold down a square of paper from corner to corner, and you
will obtain a triangle, of which two of the sides form a right angle,
and the third, or diagonal, forms an angle of 45° with each of them
(see next page). Make a mark upon the tree 5ft., or the height of your
eye, from the ground, and retire from the tree till, holding the paper
steadily with one short side horizontal and the other vertical, you can
take sight along its lower edge at the mark, and along the diagonal
side at the topmost branches; then pace or measure the distance from
the tree, add 5ft. for the height of the eye, and you will have the
height of the tree; because, if the two angles of the diagonal be 45°,
the base and the perpendicular must be equal. A piece of thin board,
with pins set in at each angle to serve as sights, would be better
than the paper, but is not so readily extemporised. If you split the
end of a wand so as to hold the paper or board quite up to the height
of your eye, it will give additional steadiness. The observer in our
illustration is unavoidably represented a little too near his work, but
he is probably taking the height of the first bifurcation, which is
often more important than the height of the tree.
[Illustration: FINDING THE HEIGHT OF A TREE BY RIFLE OR FOLDED PAPER.]
Fig. 2. Or, sticking a branch into the ground, select one of its forks,
or lash on a cross piece which shall pass through the trigger guard
behind the trigger, so that the gun may be about the height of your eye
when you aim horizontally at the mark on the tree, the trigger finger
grasping the stick for greater steadiness. Take another stick, with a
fork or cross rest of equal height with the first, and connect them by
a smaller stick of any length, say 18in. or 2ft., and at exactly the
same height above the lower rest lash another on the second stick, so
that, the base and perpendicular being equal, the gun, when its muzzle
is laid on the higher rest, shall form exactly an angle of 45° with
its line when previously laid upon the lower one. Now retire until
from the lower rest you can sight the mark upon the tree, and from the
upper its highest branches; then the distance from your pivot stick,
plus 5ft., will be the height of the tree. Our illustration purposely
shows this operation in the simplest possible form; but the frame might
be steadied by lashing on other cross bars (X fashion), and a friend
to help in moving it to a greater or less distance from the tree would
greatly assist the observer. It would be inconvenient to make this
observation kneeling. A telescope, a long straight reed, a roll of
paper, or a straight tube of any material, will answer almost as well
as the rifle. Even a clasp knife (Fig. 3), with a bit of reed stuck
into the handle where the point should reach, and resting on the point
of the half-opened blade, is better than nothing.
[Illustration: FIG. 3]
If the ground is perfectly level, and you have a looking-glass, lay it
down and level it by setting on it a basin full of water; retire till
you see the top of the tree reflected in it, then if your distance
from the mirror equals the height of your eye, the distance from the
mirror to the tree will be equal to its height. In perfectly calm
weather the basin of water will do without the mirror, or a shallow
pool or river will give an approximation; but, as the ground is always
depressed where water settles, there will be some uncertainty about the
height of the eye, which will more or less vitiate the observation, and
this will also be the case if thirsty animals rush in to disturb it,
as in our sketch. Or if the sun or moon is shining, set up a stick,
and watch till its shadow is equal to its height, or note when your
own shadow equals your height, and the height of the tree and the
length of its shadow will also be equal. But, as it may not be always
convenient to wait for this moment, the height of the tree may be
found by proportion. If the stick is 5ft. and its shadow 7ft., then
if the shadow of the tree be 70ft., its height will be 50ft.; or if
in looking at its reflection in the mirror, the height of your eye
be 5ft., and the distance 8ft., then if the distance from the mirror
to the tree be 80ft., its height is 50ft. In either of the first two
methods the same rule must be observed; the paper may be folded to a
greater angle if you cannot get far enough from the tree, or a smaller
one if you must go farther, and the same with the elevation of the
rifle. In these cases, carefully measure the base and perpendicular of
your smaller angle, and say, "as the base of the small angle is to its
perpendicular, so is the distance from the tree to its height."
Thus, as in Fig. 4 on next page, if the distance between the two rests
is 2ft. and the elevation of the rifle 1ft., the distance from the tree
must be equal to double its height.
[Illustration: FIG. 4.]
All these observations will apply to any object of which the highest
point is perpendicular to the accessible base, such as a precipice, the
wall of a fort, or the gable end of a house, but not to the peak of a
mountain, two or three miles beyond its base, nor to the pitched roof
of a house seen sideways, nor to the spire of a church, or flagstaff on
the central tower of a castle, unless the doors of these buildings be
opened so that you can continue to measure your base to a point exactly
beneath that which you have taken the angular height. Still, if the
base be not accessible, it is not impossible to measure the height,
for the distance of the object may be taken by any of the plans for
ascertaining the breadth of a river, or any of the above methods may be
performed twice over, as in Fig. 5; first, at any convenient distance,
_b_, and secondly, at a measured distance, _c_, nearer to or farther
from the object; and the easiest way of obtaining the result is to lay
down on paper the obtained angles, _d_, _e_, _f_, and _g_, _h_, _i_,
in due proportion to the measured distance, _b_, _c_, between them;
then from them to protract the angle, _d_, _g_, _a_, and continuing the
base line, find on it the point _j_, from which a perpendicular would
meet the top of the object, _a_. The distance, _b_, _c_, being known,
that of the base, _b_, _j_, and the height of the tree, _j_, _a_, will
be best found by measurement of equal parts, but bear in mind that the
result can only be an approximation to truth, for every additional
operation involves an increase of possible error.
[Illustration: FIG. 5.]
[Illustration: CORDWAY AND ONE-TREE BRIDGE.]
* * * * *
{One-tree bridge, to make.}
In passing extensive marsh tracks, few expedients surpass the so-called
American cordway, the subject of the illustration on p. 325. It is
constructed as follows from the description of material usually
abounding in marsh tracks: Trees and poles of almost any description
will be found to answer. Cut as many as is thought requisite.
Divide them into three classes--_ground poles_, _cross poles_, and
_stringers_. The ground poles should be the largest and heaviest. The
cross poles are comparatively short lengths, and lay across the ground
poles with their ends projecting some distance beyond. They are laid
closely together, and then secured and bound down by the stringers
which lay on them. A treenail driven in here and there serves to keep
all in place by nipping the cross poles tightly. The ends of the ground
poles and stringers may be either scarfed and treenailed, or laid side
by side and tied with withies or strips of suitable bark. It will be
seen, on examining the illustration, that where the roadway ends a
bridge begins. This is of the description known as a one-tree bridge,
and is made as follows: Select a tree of sufficient length to reach,
when felled, across the stream, and of fair average girth, say 9ft.;
fell it with the axe in the manner before directed, and then walk out
on the trunk and cut away all the branches from the upper surface; then
log it up into lengths of about 10ft. a sufficient number of transverse
pieces to reach, when placed side by side, from one end of the bridge
log to the other. Then in the centre of each of these make a shallow
notch by delivering right and left cuts with the axe. Next with your
auger bore two holes as wide apart as the diameter of the bridge log
will admit of. Lay your transverse piece on the main log, so that it
shall rest in the form of a true cross, with the notch in the centre
resting on the main log; then, whilst keeping the cross piece steady
with one foot, bore down the auger holes about a foot into the solid
timber. Treenails (see "Treenails, to make") are then to be placed in
the holes and driven home with a mallet or the head of the axe.
[Illustration: TREE-NAILED SWAMP BRIDGE.]
{Swamp bridge, to make.}
Another form of tree-nailed bridge, calculated for very wet or
dangerously swampy ground, is formed by laying down two lines of
stouter ground logs than those used to form the "cordway" just
described, scarfing and tree-nailing the ends together as they are
laid down. The transverse bars for the footway have a right and left
chip taken out each end from the surface which is to lay next the
ground log. They are then bored with the auger, one hole at each end
being sufficient. They are then placed closely side by side. One man
completes the hole which passes down into the log, whilst another
drives home the treenails, as shown in the annexed illustration. Earth
or sand thrown with a shovel between the cross pieces increases the
stability of the arrangement. {Treenails, to make.} Treenails have
been, and will be, frequently mentioned in the course of this work;
it will, therefore, be well here to give directions for making and
using them. To the shipwright they are invaluable, as by their aid he
unites the various planks and timbers made use of in the carrying out
of his art. In England they are usually made from straight-grained
oak, which, after being sawn into proper lengths, is split up into the
rough form of the required treenail. This, after being faced and hewn
with the adze, is passed through a double-handed cutting instrument
known as a treenail tool. A skilfully-handled axe, a spokeshave, or a
drawing knife, will, although less expeditiously, produce with ease
well rounded and serviceable treenails. In wild countries any tough
straight-grained wood may be selected for treenail making. For bridge
and roadway work pine wood will answer the purpose very fairly. A dead
log is best when it can be obtained for making these wooden holdfasts.
Cut it up into pieces the length of the proposed treenail, chop off the
bark, and split them into either three or four (as directed at p. 272),
according to the size of the log; then, with the _froe_ or axe, split
them into rough squares the length of the required treenail, round off
the curves and corners, chop off the edges at the end, so that it may
enter the auger hole freely, and the treenail is ready for use.
[Illustration: GABION BRIDGE.]
{Gabion bridge, to make.}
Rivers which are too wide to be crossed by the one-tree bridge, and
yet of inconsiderable breadth, may be crossed by the use of the gabion
bridge, which is thus constructed: First, prepare as many strong wicker
gabions as the width of the stream will render necessary. About 14ft.
apart will be found a convenient distance to place them. Their height
will depend on the depth of the water. Three feet at least should be
allowed between the surface of the stream and the upper edge of the
gabion. Where suitable poles and sticks for gabion making cannot be
obtained trees should be felled and split up, as for rails (see p.
273). The bars thus obtained should be cut up into proper lengths, and,
by the use of the axe and auger, converted into large deep crates, such
as are used for packing earthenware. These are made by boring rows of
auger holes in strong wooden bars, and then driving the sharpened ends
of the lesser bars into them until the crate is finished, no nails
or metal fastenings being required. Whether the crate or gabion is
used, the principle of construction observed in making the bridge is
the same. The first gabion, after being secured to the end of a stout
rope, is launched from the bank, and then guided, end upward, by the
aid of forked setting poles, to its proper position. Stones, pebbles,
or pieces of broken rock, are now cast pell-mell by hand into the open
mouth of the gabion, which is held down by the setting pole until fixed
in its position by the weight of the mass within it. When quite full
two or three stout poles are laid side by side for a man to walk over.
He takes up his station on the gabion, and aids in arranging the ends
of two side logs which are pushed out to him from the shore, and placed
wide enough apart to give sufficient width to the intended bridge.
Transverse bars formed of split logs are now rapidly treenailed on,
as shown in the accompanying illustration. The second gabion is now
launched from the first, the stone collectors with bags and baskets
walk out, cast their loads, and return for more, proceeding in the same
manner until the bridge is finished. {Tartar bridges, to make.} When
travelling among the Tartars we had on more than one occasion to pass
our mules and horses over rather insecure-looking bridges formed by the
natives. They were alike in construction, and were made by laying three
long strong poles, or rather small tree trunks, side by side from bank
to bank. Across these alternately (butt-end and top), as shown in the
engraving on next page, was laid a close row of tightly-bound bundles
or faggots of small brushwood. On these bundles of twigs large flat
slabs of turf, grass side upward, were placed and stamped compactly
down, forming serviceable and really good bridge ways. A small river
can be easily crossed by men on foot by simply felling a tree of
sufficient girth and length across it. Should there be a number of
packs or loads to pass across, it will be well, if the party is a large
one, to so station men along the tree trunk that they can pass the
bundles or articles from hand to hand, just as firemen hand buckets of
water, thus saving unnecessary labour. A rope stretched across greatly
aids the men in keeping their balance.
[Illustration: TARTAR POLE AND FAGGOT BRIDGE.]
{Extempore jetty, to build.}
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 at Fig. 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,
and four 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 1/2in. 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 far apart. 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, the winches are hove round, and the oxen
draw the waggon up the other shore, without even having been unyoked
during the passage.
[Illustration: 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 stem of
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.
[Illustration: 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."
[Illustration: 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.
[Illustration: POLE CHAINS.]
{Makeshift fastenings.}
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 the _Phormium 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.
[Illustration: 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 1-1/2in. 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.
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.
[Illustration: 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.
{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, in thirty 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.
[Illustration: GUANO STAGE AND FLYING RAILWAY AT ICHABOE.]
It will often happen that in the erection of some makeshift
contrivance, 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.
[Illustration: 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
be used 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.
[Illustration: DEODAR BEAM BRIDGE.]
{Deodar bridges.}
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.
[Illustration: 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,
as well 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 (see p. 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.}
Very neat and effective bridges may be made on the rafter principle,
which our engraving at p. 303 will 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 XXXX'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.
[Illustration: PLANK ARCH.]
[Illustration: 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 leads straight across a river,
and there is little use in looking for one in a hollow or under a steep
bank.
{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.
[Illustration: PORTABLE INCLINES USED IN ABYSSINIA.]
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
platforms of 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.
[Illustration: MINERS' SWING AND LADDER.]
[Illustration: INDIAN ESCAPE POLE.]
[Illustration: INDIAN SCALING LADDER.]
[Illustration: ROPE AND CHAIN LADDERS.]
{Natural bridges.}
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 had long 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. 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. 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. 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. 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.
[Illustration: PEG, BRANCH, AND LOG LADDERS.]
[Illustration: LANDING BY SWINGING DERRICK.]
{Landing 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 be such a contrivance as
this at St. Helena, by the aid of which we have often landed. The
illustration on p. 349 will 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.
[Illustration: 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 that
side 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.
[Illustration: BAMBOO CARRYING FRAME AND PARBUCKLING LOG.]
{Carrying, rolling, and parbuckling heavy spars.}
In some parts of India and China very heavy weights are carried by an
ingenious framework of bamboo. A stout pole is crossed at its ends by
two lighter ones, and each of these again by two others, each of which
is again crossed by smaller ones 2in. or 3in. in diameter and 6ft. or
8ft. long; the sixteen ends of these are raised on the shoulders of as
many men; the weight is slung to the centre of the larger beam, and
borne with ease and comfort on the elastic frame. In our illustration
(p. 352), two gangs of coolies are represented carrying a tree, but
more could be employed if requisite. For rolling, the tree should be
cleared of projecting stumps as much as possible; long skids should be
placed under it, and if the ends from which the tree is to be rolled
can be elevated by wedges or otherwise, so as to make an inclined
plane for it to roll down so much the better; at all events, get the
thick end under the tree and let the thin end be in the direction
that you wish to roll it. Parbuckling is effected by making fast the
end of a line to a stump or other holdfast in the required direction,
then bringing the end of the line under the log, and taking one or
more clear turns, bringing the end back over it and hauling on. A few
hands judiciously using handspikes or levers will greatly assist this
operation.
{Ladders.}
There are times when the principle of the common step-ladder might
be advantageously remembered; and a traveller who expected to have
much climbing might have one of those in which a groove is run in the
inside of each standard, and the rungs, working on pivots, are shut up
into it, the whole forming a light and compact pole, which a man might
easily carry on his shoulder. It would, however, be cheaper and better
to purchase this at home than to make it abroad. A rope and batten
ladder is more easily made. The rope is doubled, an eye is turned in to
the bight, holes are bored in the ends of the steps or rungs, the ends
of the rope are passed through, and double knots turned on to keep each
step in place. A light ladder, either of this kind or that previously
described, with a coil of rope to fling over the lower branches, would
enable a botanist or collector of birds or insects to climb many trees
otherwise inaccessible.
{Fire-escapes.}
In case of fire in a town, if anything--say the end of a sofa or part
of a bed frame--could be projected only 1ft. or 2ft. from a window,
and weighted by a chest of drawers on its inner end, it would form
what persons unskilled in climbing so much require--a clear point of
departure; and the blankets, sheets, and coverlets torn into strips of
not less than 4in. or 6in. wide, and twisted into a two-stranded rope,
could be fastened to this and used--first, to lower the more helpless
persons into the street, and, finally, for the active to glide down
by. It would be too much to expect, as has been proposed, that every
house should have a coil of rope, but it is well to remember that if
there be only a ball of string it may serve to haul up stronger lines,
brought by volunteers from without. If infants are to be lowered, it
is better to put them in a bag than to tie a rope round their bodies;
a couple of pillow cases would be strong enough, and there would be
no fear of suffocation during the minute or two of their descent. A
man may tie a child on his back or descend with it in his arms, but
it is much safer to lower it separately. If flames are bursting from
the windows beneath, perhaps the rope may be taken to the next lower
story of the opposite house so as to avoid the danger of burning
the rope or scorching those who descend. Of regular fire-escapes we
need say nothing, as where they are provided competent persons, very
frequently seamen, are appointed to work them; but it is well to bear
in mind that, as the property of flame and heated air is to ascend, a
man creeping close to the floor may often traverse in safety a chamber
the upper part of which is impracticable. A towel or piece of sheeting
dipped in water and tied round the mouth and nose will prevent heated
smoke and particles of burning matter from entering the air passages,
and thus enable a person to struggle for life in situations where
suffocation would be inevitable without some such expedient for its
preservation.