SHIPS.
The "cargo slave" and the "ocean greyhound" are already differentiated
by marked characteristics, and in the twentieth century the divergence
between the two types of vessels will become much accentuated. The
object aimed at by the owners of cargo boats will be to secure the
greatest possible economy of working, combined with a moderately good
rate of speed, such as may ensure shippers against having to stand out
of their capital locked up in the cargo for too long a period. Hence
cheap power will become increasingly a desideratum, and the possible
applications of natural sources of energy will be keenly scrutinised
with a view to turning any feasible plan to advantage. The sailing
ship, and the economic and constructive lines upon which it is built
and worked, will be carefully overhauled with a view to finding how
its deficiencies may be supplemented and its good points turned to
account. One result of this renewed attention will be to confirm, for
some little time, the movement which showed itself during the past
decade of the nineteenth century for an increase of sailing tonnage.
Sooner or later, however, it will be recognised that sail power must
be largely supplemented, even on the "sailer," if it is to hold its
own against steam.
For mails and passengers, on the other hand, steam must more and more
decidedly assert its supremacy. Yet the mail-packet of the twentieth
century will be very different from packets which have "made the
running" towards the close of the nineteenth. She will carry little or
no cargo excepting specie, and goods of exceptionally high value in
proportion to their weight and bulk. Nearly all her below-deck
capacity, indeed, will be filled with machinery and fuel. She will be
in other respects more like a floating hotel than the old ideal of a
ship, her cellars, so to speak, being crammed with coal and her upper
stories fitted luxuriously for sitting and bed rooms and brilliant
with the electric light. But in size she will not necessarily be any
larger than the nineteenth century type of mail steamer. Indeed the
probability is that, on the average, the twentieth century
mail-packets will be smaller, being built for speed rather than for
magnificence or carrying capacity.
The turbine-engine will be the main factor in working the approaching
revolution in mail steamer construction. The special reason for this
will consist in the fact that only by its adoption can the conditions
mentioned above be fulfilled. With the ordinary reciprocating type of
marine steam machinery it would be impossible to place, in a steamer
of moderate tonnage, engines of a size suitable to enable it to attain
a very high rate of speed, because the strain and vibration of the
gigantic steel arms, pulling and pushing the huge cranks to turn the
shafting, would knock the hull to pieces in a very short time. For
this very reason, in fact, the marine architect and engineer have
hitherto urged, with considerable force of argument, that high speed
and large tonnage must go concomitantly. Practically, only a big
steamer, with the old type of marine-engine, could be a very fast one,
and, for ocean traffic at any rate, a smaller vessel must be regarded
as out of the running. Very large tonnage being thus made a prime
necessity, it followed that the space provided must be utilised, and
this need has tended to perpetuate the combination of mail and
passenger traffic with cargo carrying.
The first step towards the revolution was taken many years ago when
the screw propeller was substituted for the paddle-wheel. The latter
means of propulsion caused shock and vibration not only owing to the
thrusts of the piston-rod from the steam-engine itself, but also from
the impact of the paddles upon the water one after the other. A great
increase in the smoothness of running was attained when the screw was
invented--a propeller which was entirely sunk in the water and
therefore exercised its force, not in shocks, but in gentle constant
pressure upon the fluid around it. Such as the windmill is for wind
and the turbine water-wheel for water was the screw propeller,
although adapted, not as a generator, but as an application of power.
Having made the work and stress continuous, the next thing to be
accomplished was to effect a similar reform in the engines supplying
the power. This is accomplished in the turbine steam-engine by causing
the steam to play in strong jets continuously and steadily upon vanes
which form virtually a number of small windmills. Thus, while the
screw outside of the hull is applying the force continuously, the
steam in the inside is driving the shafting with equal evenness and
regularity.
The steam turbine does not appear to have by any means reached
finality in its form, such questions as the angle of impact which the
jet should make with the surface of the vane, and the size of the
orifice through which the steam should be ejected, being still
debatable points. But on one matter there is hardly any room for
doubt, and that is that the best way to secure the benefit of the
expansive power of steam is to permit it to escape from a pipe having
a long series of orifices and to impinge upon a correspondingly
numerous series of vanes, or, perhaps, upon a number of vanes arranged
so that each one is long enough to receive the impact of many jets.
Hitherto the steam supply-pipe emitting the jet has been placed
outside of the circle of the wheel; but the future form seems likely
to be one in which the axis of the wheel is itself the pipe which
contains the steam, but which permits it to escape outwards to the
circumference of the wheel. The latter is, in this form of turbine,
made in the shape of a paddle-wheel of very small circumference but
considerable length, the paddles being set at such an inclination as
to obtain the greatest possible rotative impulse from the
outward-rushing steam. The pipe must be turned true at intervals to
enable it to carry a number of diminutive wheels upon which these long
vanes are mounted, and a very strong connection must be made between
these wheels and the shaft of the screw. Inasmuch as a high speed of
rotation is to be maintained, the pitch of the screw in the water is
set so as to offer but slight opposition to the water at each turn.
The immense speed attained is thus due, not to the actual power with
which the water is struck by the screw at each revolution, but to the
extraordinary rapidity with which the shaft rotates.
The twin screw, with which the best and safest of modern steam-ships
are all fitted, will soon develop into what may be called "the twin
stern". Each screw requires a separate set of engines and the main
object of the duplication is to lessen the risk of the vessel being
left helpless in case of accident to one or other. The advisability of
placing each engine and shafting in a separate water-tight compartment
has therefore been seen. At this point there presents itself for
consideration the advisability of separating the two screws by as wide
a distance as may be convenient and placing the rudder between the
two. Practically, therefore, it will be found best to build out a
steel framework from each side of the stern for holding the bearings
of each screw in connection with the twin water-tight compartments
holding the shafting; and thus will be evolved what will practically
represent a twin, or double, stern.
In the case of the turbine steamer several of the forms of screw which
were first proposed when that type of propeller was invented will
again come up for examination, notably the Archimedean screw, wound
round a fairly long piece of shafting. The larger the circular area of
this screw is the less will be the risk of "smashing" the water, or of
losing hold of it entirely in rough weather. With twin screws of the
large Archimedean type the propelling apparatus of a turbine steamer
will--if the screws are left open--be objected to on the ground of
liability to foul or to get broken in crowded fairways. Hence will
arise a demand for accommodation for each screw in a tube forming part
of the lower hull itself and open at the side for the taking in of
water, while the stern part is equally free. In this way there is
evolved a kind of compromise between the two principles of marine
propulsion, by a screw and by a jet of water thrown to sternward. The
water-jet is already very successfully employed for the propulsion of
steam lifeboats in which, owing to the danger of fouling the
life-saving and other tackle, an open screw is objectionable.
The final extermination of the sailing ship is popularly expected as
one of the first developments of the twentieth century in maritime
traffic. Steam, which for oversea trade made its entrance cautiously
in the shape of a mere auxiliary to sail power, had taken up a much
more self-assertive position long before the close of the nineteenth
century, and has driven its former ally almost out of the field in
large departments of the shipping industry. Yet a curious and
interesting counter movement is now taking place on the Pacific Coast
of America, as well as among the South Sea Islands and in several
other places where coal is exceptionally dear. Trading schooners and
barques used in these localities are often fitted with petroleum oil
engines, which enable them to continue their voyages during calm or
adverse weather. For the owners of the smaller grade of craft it was a
material point in recommendation of this movement that, having no
boiler or other parts liable to explode and wreck the vessel, an oil
engine may be worked without the attendance of a certificated
engineer. As soon as this legal question was settled a considerable
impetus was given to the extension of the auxiliary principle for
sailing ships. The shorter duration of the average voyage made by the
sail-and-oil power vessels had the effect of enabling shippers to
realise upon the goods carried more speedily than would have been
possible under the old system of sail-power alone.
It is already found that in the matter of economy of working,
including interest on cost of vessel and cargo, these oil-auxiliary
ships can well hold their own against the ordinary steam cargo slave.
Up to a certain point, the policy of relying upon steam entirely,
unaided by any natural cheap source of power, has been successful; but
the rate of speed which the best types of marine engines impart to
this kind of vessel is strictly limited, owing to considerations of
the enormous increase of fuel-consumption after passing the twelve or
fourteen mile grade. For ocean greyhounds carrying mails and
passengers the prime necessity of high speed has to a large extent
obliterated any such separating line between waste and economy. It is,
however, a mistake to imagine that the cargo steamer of the future
will be in any sense a replica of the mail-boat of to-day. The
opposition presented by the water to the passage of a vessel increases
by leaps and bounds as soon as the rate now adopted by the cargo
steamer is passed, and thus presents a natural barrier beyond which it
will not be economically feasible to advance much further.
If then we recognise clearly that steam cargo transport across the
ocean can only be done remuneratively at about one half the speed now
attained by the very fastest mail-boats, we shall soon perceive also
that the chances of the auxiliary principle, if wisely introduced,
placing the "sailer" on a level with the cargo ship worked by steam
alone, are by no means hopeless. A type of vessel which can be trusted
to make some ten or twelve knots regularly, and which can also take
advantage of the power of the wind whenever it is in its favour, must
inevitably possess a material advantage over the steam cargo slave in
economy of working, while making almost the same average passages as
its rival.
Then, also, the sailless cargo slave, in the keen competition that
must arise, will be fitted with such appliances as human ingenuity can
in future devise, or has already tentatively suggested, for invoking
the aid of natural powers in order to supplement the steam-engine and
effect a saving in fuel. One of these will no doubt be the adoption of
the heavy pendulum with universal joint movement in a special hold of
the vessel so connected with an air-compression plant that its
movements may continually work to fill a reservoir of air at a high
pressure. The marine engines of the ordinary type will then be
adapted to work with compressed air, and the true steam-engine itself
will be used for operating an air compressor on the system adopted in
mines.
The pendulum apparatus, of course, is really a device for enabling a
vessel to derive, from the power of the waves which raise her and roll
her, an impetus in the desired direction of her course. Inventions of
this description will at first be only very cautiously and partially
adopted, because if there is one thing which the master mariner fears
more than another it is any heavy moving weight in the hold, the
motions of which during a storm might possibly become uncontrollable.
When steam was first applied to the propulsion of ships the common
argument against it was that any machine worked by steam and having
sufficient power to propel a vessel would also develop so much
vibration as to pull her to pieces--to say nothing of the risk of
having her hull shattered at one fell blow by the explosion of the
steam boiler. These undoubtedly are dangers which have to be provided
against, and probably the occasional lack of care has been the cause
of many an unreported loss, as well as of recorded mishaps from broken
tail-shafts and screws, or from explosions far out at sea.
The air-compressing pendulum will no doubt be constructed on such a
principle that, whenever there is any danger of its weighty movements
getting beyond control or doing any damage to the vessel, its force
can be instantly removed at will, and the apparatus can be brought to
a standstill by the application of friction brakes and other means.
The weight may be made up of comparatively small pigs of iron, which,
through the opening of a valve controlled from the deck by the stem of
the pendulum, can be let fall out into the hold separately. The
swinging framework would then be steadied by the friction brake
gripping it gradually.
Auxiliary machinery of this class can only be made use of, as already
indicated, to a certain strictly limited extent, owing to the tendency
of any swinging weight in a vessel to aggravate the rolling during
heavy weather. Some tentative schemes have been put forward for
tapping a source of wave-power by providing a vessel with flippers,
resting upon the surface of the water outside her hull, and actuating
suitable internal machinery with the object of propulsion. A certain
amount of encouragement has been given by the performances of small
craft fitted in this way; but it is objected by sea-faring men that
the behaviour of a large vessel, encumbered with outlying parts
moving on the waves independently, would probably be very erratic
during a storm and would endanger the safety of the ship itself. No
kind of floating appendage, moving independently of the vessel, could
exercise any actual force by the uprising of a wave in lifting it
without being to some extent sunk in the water; and, accordingly, when
the waves were running high there would be imminent risk that heavy
volumes of water would get upon the apparatus and prevent the ship
from righting itself. Many of the schemes that have been put forward,
by patent and otherwise, for the automatic propulsion of ships have
entirely failed to commend themselves by reason of their taking little
or no account of the behaviour of a ship, fitted with the proposed
inventions, during very rough and trying weather.
The swinging pendulum, with connected apparatus for compressing air
or, perhaps, for generating the electric current, seems to be the most
controllable and therefore the safest of the various types of
apparatus which are applicable to the utilisation of wave-power for
propulsion. In the construction of connecting machinery by which the
movements of a pendulum hanging up from a universal joint may be
transmitted to wheels or pistons operating compressors or dynamos, it
is necessary to transform all motions passing in any direction
through the spherical or bowl-shaped figure traced out by the end of
the pendulum in the course of its swinging. This may be effected, for
instance, in the case of a pendulum working air-compressors, by
mounting the latter on bearings like those of the gun-carriage in a
field piece, and having two of them operating one at right angles to
the other. The rods which carry the air-compressing pistons are then
connected to the end of the pendulum by universal joints, and the
parts which have been likened to a gun-carriage are fixed on pivots so
as to be able to move horizontally. Air-tight joints in the pipes
which lead to the compressed air reservoir are placed in the bearings
of this mounting. We thus have the same kind of provision for taking
advantage of a universal movement in space as is made in solid
geometry by three co-ordinates at right angles to one another for
measuring such movements.
Another plan is to have the pendulum swung in a strong steel collar
and carrying at its end three or more air-compressing pumps set
radially, with the piston-rods thrust outwards by a strong spring on
each, but with the ends perfectly free from any attachment, yet fitted
with a buffer or wheel. As the pendulum moves it throws one or more
of these piston-rod ends into contact with the inner surface of the
ring, driving it into the compressing pump. At the top of the pendulum
there is a double or universal pipe-joint through which the air under
pressure is driven to the reservoir, and by which the apparatus is
also hung. This is the simplest, and in some respects the best, form.
A very simple type of the wave-power motor as applied to marine
propulsion is based upon an idea taken from the mode of progression
adopted by certain crustaceans, namely the possession of the means for
drawing in and rapidly ejecting the water. Something of the kind will
most probably be made available for assisting in the propulsion of
sailing ships which are not furnished with machinery of any type
suitable for the driving of a screw. A very much simplified form of
the pendulous or rocking weight is applicable in this case. A
considerable amount of cargo is stowed away in an inner hull, taking
the shape of what is practically a gigantic cradle rocking upon
semicircular lines of railway iron laid down in the form of ribs of
the ship. To the sides of these large rocking receptacles are
connected the rods carrying, at their other ends, the pistons of large
force-pumps which draw the water in at one stroke and force it out to
sternwards, below the water line, at the other.
In this arrangement it is obvious that only the "roll" and not the
"pitch" of the vessel can be utilised as the medium through which to
obtain propulsive force. But it is probable that fully eighty per
cent. of the movements of a vessel during a long voyage--as indicated,
say, by the direction and sweep of its mast-heads--consists of the
roll. Each ton of goods moved through a vertical distance of one foot
in relation to the hull of the vessel, has in it the potentiality of
developing, when fourteen or fifteen movements occur per minute, about
one horse-power. A cradle containing 200 tons, as may therefore be
imagined, can be made to afford very material assistance in helping
forward a sailing ship during a calm. In such tantalising weather the
"ground-swell" of the ocean usually carries past a becalmed vessel
more waste energy than is ever utilised by its sails in the briskest
and most propitious breeze.
For sailing ships especially, the rocking form of wave-motor as an aid
to propulsion will be recommended on account of the fact that when the
weather is "on the beam" both of its sources of power can be kept in
full use. The sailing vessel must tack at any rate with the object of
giving its sail power a fair chance, and thus, when it has not a fair
"wind that follows free," it must always seek to get the breeze on its
beam, and therefore usually the swell must be taking it sideways. It
would be only on rare occasions that a sailing vessel, if furnished
with rocking gear for using the wave-power, would be set to go nearer
to the teeth of the wind than she would under present conditions of
using sail-power alone. The advantage of the wave-power, however,
would be seen mainly during the calm and desultory weather which has
virtually been the means of forcing sail-power to resign its supremacy
to steam.
For checking the rocker in time of heavy weather special appliances
are necessary, which, of course, must be easily operated from the
deck. Wedge-shaped pieces with rails attached may be driven down by
screws upon the sides of the vessel, thus having the effect of
gradually narrowing the amplitude of the rocking motion until a
condition of stability with reference to the hull has been attained.
In the building of steel ships, as well as in the construction of
bridges and other erections demanding much metal-work, great economies
will be introduced by the reduction of the extent to which riveting
will be required when the full advantages of hydraulic pressure are
realised. The plates used in the building of a ship will be
"knocked-up" at one side and split at the other, with the object of
making joints without the need for using rivets to anything like the
extent at present required. In putting the plates thus treated
together to form the hull of a vessel the swollen side of one plate is
inserted between the split portions of another and the latter parts
are then clamped down by heavy hydraulic pressure. This important
principle is already successfully used in the making of rivetless
pipes, and its application to ships and bridges will be only a matter
of a comparatively short time. Through this reform, and the further
use of steel ribs for imparting strength and thus admitting of the
employment of thinner steel plates for the actual shell, the cost of
shipbuilding will be very greatly reduced.
Hoisting and unloading machines will play a notable part in minimising
the expenses of handling goods carried by sea. The grain-elevator
system is only the beginning of a revolution in this department which
will not end until the loading and unloading of ships have become
almost entirely the work of machinery. The principle of the miner's
tool known as the "sand-auger" may prove itself very useful in this
connection. From a heap of tailings the miner can select a sample, by
boring into it with a thin tube, inside of which revolves a shaft
carrying at its end a flat steel rotary scoop. The auger, after
working its way to the bottom of the heap, is raised, and, of course,
it contains a fair sample of the sand at all depths from the top
downwards. On a somewhat similar principle the unloading of ships
laden with grain, ore, coal, and all other articles which can be
handled in bulk and divided, will be carried out by machines which, by
rotary action, will work their way down to the bottom of the hull and
will then be elevated by powerful lifting cranes. For other classes of
goods permanent packages and tramways will be provided in each ship,
and trucks will be supplied at the wharf.
For coastal passages across shallow but rough water like the English
Channel, the services of moving bridges will be called into
requisition. One of these has been at work at St. Malo on the French
coast opposite Jersey, and another was more recently constructed on
the English coast near Brighton. For the longer and much more
important service across the Channel submarine rails may be laid down
as in the cases mentioned, but in addition it will be necessary to
provide for static stability by fixing a flounder-shaped pontoon just
below the greatest depth of wave disturbance, and just sufficient in
buoyancy to take the great bulk of the weight of the structure off the
rails. In this way passengers may be conveyed across straits like the
Channel without the discomforts of sea-sickness.
The stoking difficulties on large ocean-going steamers have become so
acute that they now suggest the conclusion that, notwithstanding
repeated failures, a really effective mechanical stoker will be so
imperatively called for as to enforce the adoption of any reasonably
good device. The heat, grime, and general misery of the stoke-hole
have become so deterrent that the difficulty of securing men to
undertake the work grows greater year by year, and in recruiting the
ranks of the stokers resort had to be had more and more to those
unfortunate men whose principal motive for labour is the insatiable
desire for a drinking bout. On the occasions of several shipwrecks in
the latter part of the nineteenth century disquieting revelations took
place showing how savagely bitter was the feeling of the stoke-hole
towards the first saloon. As soon as the mechanical fuel-shifter has
been adopted, and the boilers have been properly insulated in order to
prevent the overheating of the stoke-hole, the stoker will be raised
to the rank of a secondary engineer, and his work will cease to be
looked upon as in any sense degrading.
On the cargo-slave steamer and sailer a similar social revolution will
be brought about by the amelioration of the conditions under which the
men live and work. Already some owners and masters have begun to
mitigate, to a certain extent, the embargo which the choice of a
sea-faring life has in times past been understood to place upon
married men. Positions are found for women as stewardesses and in
other capacities, and it is coming to be increasingly recognised that
there is a large amount of women's work to be done on board a ship.
By and by, when it is found that the best and steadiest men can be
secured by making some little concessions to their desire for a
settled life and their objections to the crimp and the "girl at every
port," and all the other squalid accessories so generally attached in
the popular mind to the seaman's career, there will be a serious
effort on the part of owners to remodel the community on board of a
ship on the lines of a village. There will be the "Ship's Shop" and
the "Ship's School," the "Ship's Church" and various other
institutions and societies.
Thus in the twentieth century the sea will no longer be regarded, to
the same extent as in the past, as the refuge for the ne'er-do-well of
the land-living populace; and this, more than perhaps anything else,
will help to render travelling by the great ocean highways safe and
comfortable. It is a common complaint on the part of owners that by
far the larger part of maritime disasters are directly traceable to
misconduct or neglect of duty on the part of masters, officers or
crew; but they have the remedy in their own hands.