the name submarine may with real appropriateness be applied, for,
sinking in water 100 feet deep, it can remain below and run upon three
wheels along the bottom of the sea. This is the _Argonaut_, invented
by Mr. Simon Lake of Baltimore, and its main portion consists of a
steel framework of cylindrical form which is surmounted by a flat,
hollow steel deck. During submersion the deck is filled with water and
thus saved from being crushed by outside pressure as well as helping
to sink the craft.
When moving on the surface it has the appearance of an ordinary ship,
with its two light masts, a small conning-tower on which is the
steering-wheel, bowsprit, ventilators, a derrick, suction-pump, and
two anchors. A gasolene engine of special design is used for both
surface and submerged cruising under ordinary circumstances, but in
time of war storage batteries are available. An electric dynamo
supplies light to the whole interior, including a 4000 candle-power
searchlight in the extreme bow which illuminates the pathway while
under water.
On the boat being stopped and the order given to submerge, the crew
first throw out sounding lines to make sure of the depth. They then
close down external openings, and retreat into the boat through the
conning-tower, within which the helmsman takes his stand, continuing
to steer as easily as when outside. The valves which fill the deck and
submersion tanks are opened, and the _Argonaut_ drops gently to the
floor of the ocean. The two apparent masts are in reality 3-inch iron
pipes which rise thirty feet or more above the deck, and so long as no
greater depth is attained, they supply the occupants with fresh air
and let exhausted gases escape, but close automatically when the water
reaches their top.
Once upon the bottom of the sea this versatile submarine begins its
journey as a tricycle. It is furnished with a driving-wheel on either
side, each of which is 6-1/2 feet in diameter and weighs 5000 lbs.;
and is guided by a third wheel weighing 2000 lbs. journalled in the
rudder. On a hard bottom or against a strong tide the wheels are most
effective owing to their weight, but in passing through soft sand or
mud the screw propeller pushes the boat along, the driving-wheels
running “loose.” In this way she can travel through even waist-deep
mud, the screw working more strongly than on the surface, because it
has such a weight of water to help it, and she moves more easily
uphill.
In construction the _Argonaut_ is shaped something like a huge cigar,
her strong steel frames, spaced twenty inches apart, being clad with
steel plates 3/8-inch thick double riveted over them. Great strength
is necessary to resist the pressure of superincumbent water, which at
a depth of 100 feet amounts to 44 lbs. per square inch.
Originally she was built 36 feet long, but was subsequently lengthened
by some 20 odd feet, and has 9 feet beam. She weighs fifty-seven tons
when submerged. A false section of keel, 4000 lbs. in weight, can on
emergency be instantly released from inside; and two downhaul weights,
each of 1000 lbs., are used as an extra precaution for safety when
sinking in deep water.
The interior is divided into various compartments, the living quarters
consisting of the cabin, galley, operating chamber and engine-room.
There are also a division containing stores and telephone, the
intermediate, and the divers’ room. The “operating” room contains the
levers, handwheels, and other mechanism by which the boat’s movements
are governed. A water gauge shows her exact depth below the surface; a
dial on either side indicates any inclination from the horizontal.
Certain levers open the valves which admit water to the ballast-tanks
in the hold; another releases the false keel; there is a cyclometer to
register the wheel travelling, and other gauges mark the pressure of
steam, speed of engines, &c.
A compass in the conning-tower enables the navigator to steer a true
course whether above or below the surface. This conning-tower, only
six feet high, rises above the centre of the living quarters, and is
of steel with small windows in the upper part. Encircling it to about
three-quarters of its height is a reservoir for gasolene, which feeds
into a smaller tank within the boat for consumption. The compressed
air is stored in two Mannesmann steel reservoirs which have been
tested to a pressure of 4000 lbs. per square inch. This renews the
air-supply for the crew when the _Argonaut_ is long below, and also
enables the diving operations to be carried on.
The maximum speed at which the _Argonaut_ travels submerged is five
knots an hour, and when she has arrived at her destination--say a
sunken coal steamer--the working party pass into the “intermediate”
chamber, whose air-tight doors are then closed. A current of
compressed air is then turned on until the air is equal in pressure to
that in the divers’ room. The doors of this close over india rubber to
be air and water-tight; one communicates with the “intermediate,” the
other is a trap which opens downwards into the sea. Through three
windows in the prow those remaining in the room can watch operations
outside within a radius varying according to the clearness of the
water. The divers assume their suits, to the helmets of which a
telephone is attached, so arranged that they are able to talk to each
other as well as to those in the boat. They are also provided with
electric lamps, and a brilliant flood of light streams upon them from
the bows of the vessel. The derrick can be used with ease under water,
and the powerful suction-pump will “retrieve” coal from a submerged
vessel into a barge above at the rate of sixty tons per hour.
It will thus be seen how valuable a boat of this kind may be for
salvage operations, as well as for surveying the bottom of harbours,
river mouths, sea coasts, and so on. In war time it can lay or examine
submarine mines for harbour defence, or, if employed offensively, can
enter the enemy’s harbour with no chance of detection, and there
destroy his mines or blow up his ships with perfect impunity.
To return the _Argonaut_ to the surface it is only necessary to force
compressed air into the space below the deck and the four tanks in the
hold. Her buoyancy being thus gradually restored she rises slowly and
steadily till she is again afloat upon the water, and steams for land.
We have now glanced briefly at some of the most interesting
attempts--out of many dozens--to produce a practicable submarine
vessel in bygone days; and have inquired more closely into the
construction of several modern designs; among these the _Holland_ has
received especial attention, as that is the model adopted by our
Admiralty, and our own new boats only differ in detail from their
American prototype. But before quitting this subject it will be well
to consider what is required from the navigating engineer, and how far
present invention has supplied the demand.
[Illustration: _The “Holland” Submarine in the last stages of
submersion._]
The perfect submarine of fiction was introduced by Jules Verne, whose
_Nautilus_ remains a masterpiece of scientific imagination. This
marvellous vessel ploughed the seas with equal power and safety,
whether on the surface or deeply sunk beneath the waves, bearing the
pressure of many atmospheres. It would rest upon the ocean floor while
its inmates, clad in diving suits, issued forth to stroll amid aquatic
forests and scale marine mountains. It gathered fabulous treasures
from pearl beds and sunken galleons; and could ram and sink an
offending ship a thousand times its size without dinting or loosening
a plate on its own hull. No weather deflected its compass, no movement
disturbed its equilibrium. Its crew followed peacefully and cheerfully
in their spacious cabins a daily round of duties which electric power
and automatic gear reduced to a minimum. Save for the misadventure of
a shortened air-supply when exploring the Polar pack, and the clash of
human passions, Captain Nemo’s guests would have voyaged in a
floating paradise.
Compare with this entrancing creation the most practical vessels of
actual experiment. They are small, blind craft, groping their way
perilously when below the surface, the steel and electrical machinery
sadly interfering with any trustworthy working of their compass, and
the best form of periscope hitherto introduced forming a very
imperfect substitute for ordinary vision.
Their speed, never very fast upon the surface, is reduced by
submersion to that of the oldest and slowest gunboats. Their radius of
action is also circumscribed--that is, they cannot carry supplies
sufficient to go a long distance, deal with a hostile fleet, and then
return to headquarters without replenishment.
Furthermore, there arise the nice questions of buoyancy combined with
stability when afloat, of sinking quickly out of sight, and of keeping
a correct balance under water. The equilibrium of such small vessels
navigating between the surface and the bottom is extremely sensitive;
even the movements to and fro of the crew are enough to imperil them.
To meet this difficulty the big water-ballast tanks, engines and
accumulators are necessarily arranged at the bottom of the hull, and a
pendulum working a helm automatically is introduced to keep it
longitudinally stable.
To sink the boat, which is done by changing the angle of the
propeller in the _Goubet_ and some others, and by means of horizontal
rudders and vanes in the _Nordenfelt_ and _Holland_, it must first be
most accurately balanced, bow and stern exactly in trim. Then the boat
must be put into precise equilibrium with the water--_i.e._ must weigh
just the amount of water displaced. For this its specific gravity must
be nearly the same as that of the water (whether salt or fresh), and a
small accident might upset all calculations. Collision, even with a
large fish, could destroy the steering-gear, and a dent in the side
would also tend to plunge it at once to destruction.
Did it escape these dangers and succeed in steering an accurate course
to its goal, we have up to now little practical proof that the mere
act of discharging its torpedo--though the weight of the missile is
intended to be automatically replaced immediately it drops from the
tube--may not suffice to send the vessel either to bottom or top of
the sea. In the latter case it would be within the danger zone of its
alarmed enemy and at his mercy, its slow speed (even if uninjured)
leaving it little chance of successful flight.
But whatever the final result, one thing is certain, that--untried as
it is--the possible contingency of a submarine attack is likely to
shake the _morale_ of an aggressive fleet.
“When the first submarine torpedo-boat goes into action,” says Mr.
Holland, “she will bring us face to face with the most perplexing
problem ever met in warfare. She will present the unique spectacle,
when used in attack, of a weapon against which there is no defence....
You can send nothing against the submarine boat, not even itself....
You cannot see under water, hence you cannot fight under water. Hence
you cannot defend yourself against an attack under water except by
running away.”
This inventor is, however, an enthusiast about the future awaiting the
submarine as a social factor. His boat has been tested by long voyages
on and below water with complete success. The _Argonaut_ also upon one
occasion travelled a thousand miles with five persons, and proved
herself “habitable, seaworthy, and under perfect control.”
Mr. Holland confidently anticipates in the near future a Channel
service of submerged boats run by automatic steering-gear upon cables
stretched from coast to coast, and eloquently sums up its advantages.
The passage would be always practicable, for ordinary interruptions
such as fog and storms cannot affect the sea depths.
An even temperature would prevail summer and winter, the well-warmed
and lighted boats being also free from smoke and spray.
No nauseating smells would proceed from the evenly-working electric
engines. No motion cause sea-sickness, no collision be apprehended--as
each line would run on its own cable, and at its own specified depth,
a telephone keeping it in communication with shore.
In like manner a service might be plied over lake bottoms, or across
the bed of wide rivers whose surface is bound in ice. Such is the
submarine boat as hitherto conceived for peace or war--a daring
project for the coming generation to justify.
ANIMATED PICTURES.
Has it ever occurred to the reader to ask himself why rain appears to
fall in streaks though it arrives at earth in drops? Or why the
glowing end of a charred stick produces fiery lines if waved about in
the darkness? Common sense tells us the drop and the burning point
cannot _be_ in two places at one and the same time. And yet apparently
we are able to see both in many positions simultaneously.
This seeming paradox is due to “persistence of vision,” a phenomenon
that has attracted the notice of scientific men for many centuries.
Persistence may be briefly explained thus:--
The eye is extremely sensitive to light, and will, as is proved by the
visibility of the electric spark, lasting for less than the millionth
part of a second, _receive_ impressions with marvellous rapidity.
But it cannot get rid of these impressions at the same speed. The
duration of a visual impression has been calculated as one-tenth to
one-twenty-first of a second. The electric spark, therefore, appears
to last much longer than it really does.
Hence it is obvious that if a series of impressions follow one another
more rapidly than the eye can free itself of them, the impressions
will overlap, and one of four results will follow.
(_a_) _Apparently uninterrupted presence_ of an image if the
same image be repeatedly represented.
(_b_) _Confusion_, if the images be all different and
disconnected.
(_c_) _Combination_, if the images of two or a very few objects
be presented in regular rotation.
(_d_) _Motion_, if the objects be similar in all but one part,
which occupies a slightly different portion in each
presentation.
In connection with (_c_) an interesting story is told of Sir J.
Herschel by Charles Babbage:--[4]
[4] Quoted from Mr. Henry V. Hopwood’s “Living Pictures,” to
which book the author is indebted for much of his information
in this chapter.
“One day Herschel, sitting with me after dinner, amusing himself by
spinning a pear upon the table, suddenly asked whether I could show
him the two sides of a shilling at the same moment. I took out of my
pocket a shilling, and holding it up before the looking-glass, pointed
out my method. ‘No,’ said my friend, ‘that won’t do;’ then spinning my
shilling upon the table, he pointed out his method of seeing both
sides at once. The next day I mentioned the anecdote to the late Dr.
Fitton, who a few days after brought me a beautiful illustration of
the principle. It consisted of a round disc of card suspended between
two pieces of sewing silk. These threads being held between the finger
and thumb of each hand, were then made to turn quickly, when the disc
of card, of course, revolved also. Upon one side of this disc of card
was painted a bird, upon the other side an empty bird-cage. On turning
the thread rapidly the bird appeared to have got inside the cage. We
soon made numerous applications, as a rat on one side and a trap on
the other, &c. It was shown to Captain Kater, Dr. Wollaston, and many
of our friends, and was, after the lapse of a short time, forgotten.
Some months after, during dinner at the Royal Society Club, Sir Joseph
Banks being in the chair, I heard Mr. Barrow, then secretary to the
Admiralty, talking very loudly about a wonderful invention of Dr.
Paris, the object of which I could not quite understand. It was called
the Thaumatrope, and was said to be sold at the Royal Institution, in
Albemarle Street. Suspecting that it had some connection with our
unnamed toy I went next morning and purchased for seven shillings and
sixpence a thaumatrope, which I afterwards sent down to Slough to the
late Lady Herschel. It was precisely the thing which her son and Dr.
Fitton had contributed to invent, which amused all their friends for a
time, and had then been forgotten.”
The _thaumatrope_, then, did nothing more than illustrate the power of
the eye to weld together a couple of alternating impressions. The toys
to which we shall next pass represent the same principle working in a
different direction towards the production of the living picture.
Now, when we see a man running (to take an instance) we see the _same_
body and the same legs continuously, but in different positions, which
merge insensibly the one into the other. No method of reproducing that
impression of motion is possible if only _one_ drawing, diagram, or
photograph be employed.
A man represented with as many legs as a centipede would not give us
any impression of running or movement; and a blur showing the
positions taken successively by his legs would be equally futile.
Therefore we are driven back to a _series_ of pictures, slightly
different from one another; and in order that the pictures may not be
blurred a screen must be interposed before the eye while the change
from picture to picture is made. The shorter the period of change, and
the greater the number of pictures presented to illustrate a single
motion, the more realistic is the effect. These are the general
principles which have to be observed in all mechanism for the
production of an illusory effect of motion. The persistence of vision
has led to the invention of many optical toys, the names of which, in
common with the names of most apparatus connected with the living
picture, are remarkable for their length. Of these toys we will select
three for special notice.
In 1833 Plateau of Ghent invented the _phenakistoscope_, “the thing
that gives one a false impression of reality”--to interpret this
formidable word. The phenakistoscope is a disc of card or metal round
the edge of which are drawn a succession of pictures showing a man or
animal in progressive positions. Between every two pictures a narrow
slit is cut. The disc is mounted on an axle and revolved before a
mirror, so that a person looking through the slits see one picture
after another reflected in the mirror.
The _zoetrope_, or Wheel of Life, which appeared first in 1860, is a
modification of the same idea. In this instrument the pictures are
arranged on the inner side of a hollow cylinder revolving on a
vertical axis, its sides being perforated with slits above the
pictures. As the slit in both cases caused distortion M. Reynaud, a
Frenchman, produced in 1877 the _praxinoscope_, which differed from
the zoetrope in that the pictures were not seen directly through
slits, but were reflected by mirrors set half-way between the pictures
and the axis of the cylinder, a mirror for every picture. Only at the
moment when the mirror is at right angles to the line of sight would
the picture be visible. M. Reynaud also devised a special lantern for
projecting praxinoscope pictures on to a screen.
These and other somewhat similar contrivances, though ingenious, had
very distinct limitations. They depended for their success upon the
inventiveness and accuracy of the artist, who was confined in his
choice of subject; and could, owing to the construction of the
apparatus, only represent a small series of actions, indefinitely
repeated by the machine. And as a complete action had to be crowded
into a few pictures, the changes of position were necessarily abrupt.
To make the living picture a success two things were needed; some
method of securing a very rapid series of many pictures, and a machine
for reproducing the series, whatever its length. The method was found
in photography, with the advance of which the living picture’s
progress is so closely related, that it will be worth while to notice
briefly the various improvements of photographic processes. The
old-fashioned Daguerreotype process, discovered in 1839, required an
exposure of half-an-hour. The introduction of wet collodion reduced
this tax on a sitter’s patience to ten seconds. In 1878 the dry plate
process had still further shortened the exposure to one second; and
since that date the silver-salt emulsions used in photography have had
their sensitiveness to light so much increased, that clear pictures
can now be made in one-thousandth of a second, a period minute enough
to arrest the most rapid movements of animals.
By 1878, therefore, instantaneous photography was ready to aid the
living picture. Previously to that year series of photographs had been
taken from posed models, without however extending the choice of
subjects to any great extent. But between 1870 and 1880 two men, Marey
and Muybridge, began work with the camera on the movements of horses.
Marey endeavoured to produce a series of pictures round the edge of
one plate with a single lens and repeated exposures.[5] Muybridge, on
the other hand, used a series of cameras. He erected a long white
background parallel to which were stationed the cameras at equal
distances. The shutters of the cameras were connected to threads laid
across the interval between the background and the cameras in such a
manner that a horse driven along the track snapped them at regular
intervals, and brought about successive exposures. Muybridge’s method
was carried on by Anschütz, a German, who in 1899 brought out his
electrical Tachyscope, or “quick-seer.” Having secured his negatives
he printed off transparent positives on glass, and arranged these last
round the circumference of a large disc rotating in front of a screen,
having in it a hole the size of the transparencies. As each picture
came opposite the hole a Geissler tube was momentarily lit up behind
it by electrical contact, giving a fleeting view of one phase of a
horse’s motion.
[5] A very interesting article in the May, 1902, issue of
_Pearson’s Magazine_ deals with the latest work of Professor
Marey in the field of the photographic representation of the
movements of men, birds, and quadrupeds.
The introduction of the ribbon film in or about 1888 opened much
greater possibilities to the living picture than would ever have
existed had the glass plate been retained. It was now comparatively
easy to take a long series of pictures; and accordingly we find
Messrs. Friese-Greene and Evans exhibiting in 1890 a camera capable of
securing three hundred exposures in half a minute, or ten per second.
The next apparatus to be specially mentioned is Edison’s Kinetoscope,
which he first exhibited in England in 1894. As early as 1887 Mr.
Edison had tried to produce animated pictures in a manner analogous to
the making of a sound-record on a phonograph (see p. 56). He wrapped
round a cylinder a sheet of sensitized celluloid which was covered,
after numerous exposures, by a spiral line of tiny negatives. The
positives made from these were illuminated in turn by flashes of
electric light. This method was, however, entirely abandoned in the
perfected kinetoscope, an instrument for viewing pictures the size of
a postage stamp, carried on a continuously moving celluloid film
between the eye of the observer and a small electric lamp. The
pictures passed the point of inspection at the rate of forty-six per
second (a rate hitherto never approached), and as each picture was
properly centred a slit in a rapidly revolving shutter made it visible
for a very small fraction of a second. Holes punched at regular
intervals along each side of the film engaged with studs on a wheel,
and insured a regular motion of the pictures. This principle of a
perforated film has been used by nearly all subsequent manufacturers
of animatographs.