FLOATING LIGHTHOUSES
Hand in hand with the development of the unattended light for service
on land positions has proceeded the adaptation of the floating
light. This may be described briefly as an enlarged edition of the
lighted buoy, which is such a conspicuous feature of our harbours and
estuaries. Yet it is more than a buoy. It can fulfil all the purposes
of a light-vessel, both as regards the emission of a ray of light or a
distinctive sound, so that both audible and visual warning are given
simultaneously. These lights likewise are automatic in their action,
and, when set going, require no further attention for some time. Nine
months or more are often permitted to pass without human hands touching
them, and they have solved some very abstruse problems in connection
with coast lighting.
For instance, there is probably no such lonely stretch of coastline as
that of British Columbia and Alaska. There is only one large port north
of Vancouver--Prince Rupert--and this rising hive of maritime activity
is 550 miles distant. The coast is as wild as that of Norway, which,
indeed, it resembles very closely, bristling as it does with fjords and
islands, with rugged cliffs rising abruptly from the water to a height
of several hundred feet. Navigation at night is extremely hazardous,
as the path leads by devious ways through deep channels intersecting
the outer barriers of islands, where fogs hang low and thickly. The
captain has to pick his way carefully, determining his course by timing
the period between the blast of his siren and its echo, as it is
thrown from headland to headland. As the passenger traffic developed,
the masters of the vessels entrusted with so many human lives felt
the increased responsibility keenly, and agitated for more adequate
protection. The erection of lighthouses, even of the most economical
type, would have entailed huge expenditure by both the United States
and Canadian Governments, while the question of maintenance would have
bristled with searching problems.
Accordingly, it was decided to adopt the floating automatic system,
which had proved eminently satisfactory in other parts of the world.
In this manner a highly successful and inexpensive solution of the
difficulty was found. These buoys have been installed at all the most
treacherous points leading to sounds and canals, as the lochs are
called, and have been found in every way equal to the simplest type
of attended lighthouse. The southern coast of Nova Scotia has been
protected in a similar manner, a chain of automatic lights, spaced ten
miles apart, having been completed, so that this wild, rugged shore
is patrolled very efficiently at the present moment. Other countries
have not been dilatory in adopting the same methods. Consequently,
to-day the automatic floating lighthouse is one of the handiest, most
efficient and reliable devices for assisting navigation that the
lighthouse engineer has at his command.
The lights assume different forms, this factor being influenced by
position, specific duty, and local conditions. Similarly, the character
of the illuminant employed also varies, acetylene, compressed oil-gas,
petroleum, and electricity, being utilized, according to circumstances.
On the whole, however, acetylene gas appears to be the most favoured
illuminating medium, inasmuch as the preparation of the carbide of
calcium has undergone such marked improvement.
When Mr. Thomas L. Willson discovered the cheap process for the
manufacture of carbide of calcium upon a commercial scale, and the
new industry became placed upon a firm footing, it was only natural
that the inventor should realize the possibilities of applying the
new illuminant to the assistance of navigation. Acetylene gas gives
a brilliant clear light of intense whiteness, which is capable of
penetrating a great distance. Accordingly, he set to work to devise
a buoy lighted by this gas, and able to carry sufficient storage of
calcium carbide to burn for weeks or months without attention. When
he had completed the first apparatus of this character, he handed it
over to the Marine Department of the Canadian Government for submission
to any test that they might consider expedient, in order to ascertain
the limits of its application. The buoy was set in position and
watched carefully. Periodically it was examined to ascertain whether
overhauling and cleaning were necessary, as well as the behaviour
of the light under all conditions of weather. Captains of vessels
passing the beacon were requested to pronounce their opinions upon the
quality of the light, and their remarks concerning its range, facility
with which it might be picked up, reliability, and so forth, were
carefully marshalled and digested by the authorities. Precisely what
the officials thought of the invention is reflected most convincingly
by the fact that to-day over 300 lights working upon this principle are
stationed in Canadian waters, both upon the storm-bound ocean coasts
and upon the wind-swept shores of the Great Lakes and waterways.
[Illustration: FIG. 16.--SECTIONAL ELEVATION OF THE WILLSON AUTOMATIC
FLOATING LIGHT. (See next page.)]
The Willson buoys are absolutely automatic in their operation. All
the impurities in the gas are removed by passing it through a special
purifier, so that the burner cannot become clogged or the light
impoverished. A charge of 1,300 to 1,500 pounds of carbide is carried
within the apparatus, and the gas is generated _under low pressure_.
The lantern is fitted with a Fresnel lens, so that the light is
condensed into an intensely powerful and penetrating horizontal beam.
One prominent feature is that the candle-power of acetylene gas is
seven times as high as that of compressed oil-gas, while the reservoir
of a given size will contain this equivalent of more light. The
candle-power of these floating lights obviously varies, the largest
size being capable of emitting a beam of 1,000 candle-power, this flame
being the maximum that the lens will stand without breaking.
The construction and the principle of operation are exceedingly simple,
as may be gathered from reference to Fig. 16. The beacon comprises
a gas generator tube of steel (1), which is supported by the steel
float chamber (2), on the upper side of which is placed the support
(3) carrying the lantern (4). Stability is insured by means of the
counterweight (6) attached to the lower end of the generator tube.
A few feet from the bottom of the latter is a diaphragm (7), fitted
centrally with a conically-seated valve (8) which is mounted on a stem
(9). This extends through the centre of the generator and its head
(10). The upper end of the valve stem carries a hexagonal nut (11),
while the stem itself at this point has a keyway cut into it. A spline
is fitted into the generator head to engage the keyway, and when the
nut (11) is turned to close or to open the valve, the stem itself
cannot move with it, except in two directions only--up or down. The nut
itself cannot be turned too far, in which event it might drop the stem
and valve, as there is a stop-collar (12). Leakage of gas is prevented
by a cap (14), which is screwed into the generator head and sealed with
a rubber washer. This cap is sufficiently long to permit the valve stem
to be raised or lowered so as to adjust the movement of the valve. The
stem of the valve is protected from the carbide by enclosure within
a tube (13), which works through a guide bar (24) bolted to the side
of the generator tube. A grid (23) is fitted in the centre of the
diaphragm (7) and surrounding the valve (8), so as to prevent small
pieces of carbide, which may pass through the grate (16), from falling
into the water, and thereby being wasted. The steel grate upon which
the carbide rests is attached to the inside of the generator, a short
distance above the diaphragm. The grid (23) also acts as a valve seat,
and is provided with a rubber packing (15), which is held in a groove
in the seat, and projects a sufficient distance to make a good joint
with the valve (8) when it is closed, even if the valve happen to be
foul.
The carbide of calcium, in the form of large crystals measuring about
8 by 4 inches, is placed in the generator tube when the beacon is
immersed in the water, the valve (8) being opened and the valve-cap
(14) screwed down. In the centre of the counterweight (6) is an orifice
through which the water enters from the outside, and passes through
the open valve, to come into contact with the carbide resting upon the
grate. Gas is generated instantly, to ascend through the carbide into
the purifying chamber (5), where all deleterious matter is removed, the
gas escaping thence through the small aperture (17) and pipe (18) to
the lantern, to which the supply-pipe is connected by the aid of the
coupling (19).
Of course, at times gas is liable to be generated more rapidly than
it can be consumed. What happens? The apparatus is not provided with
facilities to receive the surplus gas. Being unable to escape upwards
through the generator tube, it collects at the bottom, and as the
pressure increases it gradually forces the water away from the carbide,
so that generation ceases, and is not resumed until the surplus gas has
been absorbed, when the water once more is able to come into contact
with the carbide. Thus it will be seen that the gas generation is
controlled automatically, and that it is almost impossible for the gas
pressure within the plant to reach a disruptive degree, owing to the
fact that when it exceeds a certain limit it has a free vent from the
bottom of the device, where the water normally is permitted to enter to
carry out its designed purpose.
This invention has been utilized for a wide variety of purposes, from
the lighting of harbours, navigable channels, rivers, bays, and so
forth, to that of exposed coasts. The automatic beacon, properly so
called, has a tower, which brings the focal plane to an elevation
varying between 50 and 100 feet, this tower being built of lattice
steelwork attached to the top half of the buoy, with a day mark
surrounding the lantern gallery, access to which is secured by an iron
ladder. This type of light carries a sufficient storage of carbide
in a single charge to keep the light burning continuously for about
forty weeks. In this instance the only modification from that already
described is that the water for the production of the gas is admitted
into the top instead of to the bottom of the generator. When an excess
of gas occurs, the pressure thereof drives the water away from the
carbide until the surplus has been consumed. Another type, somewhat
smaller, carrying a charge sufficient for nearly six months, has proved
highly successful as a coastal light, some thirty beacons of this class
being stationed along the shore of British Columbia. The only trouble
experienced therewith in these waters has been due to frost, which,
solidifying the water around the buoy, has interrupted the designed
functions.
But probably the most complete and useful type of Willson acetylene
gas beacon is that in which the Courtenay whistling device is
incorporated, so that in thick weather audible warning of the danger
may be extended. In this instance the floating chamber which supports
the superstructure carrying the light and also the generator tube, is
fitted with two further tubes which project from the base like huge
legs. These tubes are open at the bottom, but are closed at the top
except for a connection with a valve-casing, which is fitted with a
ball-valve, and upon which a powerful whistle is bolted. Now, if the
buoy is lowered and anchored in absolutely still water, the water will
rise to the same level within the tubes as it is outside; but when the
buoy is lifted upon the crest of a wave, the level of the water falls,
so that the air space within the tubes is increased. Air enters this
augmented space through the ball-check inlet valve in the valve-casing.
When the beacon falls, naturally the water endeavours to maintain its
level within the tubes, and therefore the air which was admitted into
the space becomes compressed, to be expelled through the only possible
vent--the whistle--thereby producing a very powerful blast. Thirty of
these combined light and whistling buoys have been strung along the
rugged Nova Scotia coast, and have proved highly popular, that outside
Halifax harbour being known colloquially among seafarers as the “Outer
Automatic.”
Another acetylene system, but working upon a better principle, has been
perfected in Sweden, and, indeed, now has been adopted universally,
owing to its many excellent features. This is the “Aga” light, which
is the invention of Mr. Gustaf Dalén,[C] and which has been brought
to a high stage of commercial success by the Gas Accumulator Company
of Stockholm. I have pointed out the one objection to the Willson
acetylene automatic light--namely, its uselessness when the surrounding
water becomes frozen. While this drawback does not affect its sphere
of utility to a noticeable degree in Canadian waters, it acts somewhat
adversely in other seas where similar conditions prevail, but where
the navigable channels are kept open by ice-breakers, such as, for
instance, in the Baltic Sea. Mr. Dalén recognized this weak point in
any system wherein contact with water is responsible for the generation
of the gas, and accordingly sought for a superior method. Fortunately,
the perfection of a new means of handling acetylene, by French
inventors, offered the complete solution of the problem in a practical
way. The principle of this lies in the use of dissolved acetylene,
which is perfectly safe from explosion, and can be handled with the
greatest facility. The gas can be stored in cylinders similar to those
used for containing oxygen and hydrogen under pressure, gases which
are easier to transport than carbide of calcium, and, what is far more
important, climatic conditions do not exercise the slightest influence
upon it.
[C] The humane labours of Mr. Dalén received recognition by the
award of the Nobel Peace Prize in 1912.
Dissolved acetylene may be stored within the cylinder, or accumulator,
as it is called, to a pressure of at least ten atmospheres, and at
this pressure it contains 100 times its own volume of acetylene gas.
The accumulators may be made of any desired size, this factor being
governed by considerations of transport and application, as well as of
the consumption of the burner.
The perfection of the dissolved acetylene process came as a great boon
to the Swedish lighting authorities, inasmuch as they have probably
the most difficult stretch of coastline in the world to protect. At the
same time, owing to the wild, exposed character of many of the points
which demanded lighting, a perfect, economical, and reliable automatic
system was in urgent demand. Acetylene was an obvious illuminant,
since, while the country is deficient in the essential resources for
the preparation of other fuels, carbide of calcium is very cheap,
Sweden, in fact, being the largest producer of this commodity. The
Swedish Board of Pilotage experimented with acetylene lighting for six
or seven years, submitting every known acetylene lighting system to
searching practical trials, but failed to be sufficiently convinced on
the vital question of reliability. Freezing-up was the most pronounced
shortcoming, but when dissolved acetylene appeared as a commercial
product this disadvantage was removed completely, and acetylene was
adopted.
[Illustration: THE “KALKGRUNDET,” SWEDEN’S LATEST AUTOMATIC LIGHTSHIP.
The Dalén Flasher is used, and this undoubtedly is the finest vessel of
its type in the world.]
Yet dissolved acetylene, though completely successful, possessed one
drawback. It was expensive as compared with oil-gas. Accordingly, there
was great scope for a means of economizing the consumption of the fuel
without interfering with its lighting value and efficiency. At the same
time a superior flashing system was desired. The methods which were
in vogue to this end were satisfactory so far as they went, but they
involved a considerable useless consumption of gas.
This is where Mr. Gustaf Dalén completed one of his greatest
achievements. He perfected a flashing apparatus wherein the gas passes
to the burner in intermittent puffs, to be ignited by a small invisible
pilot light. The device was tested and proved so successful that it
was adopted throughout the service. In Swedish waters to-day there are
127 aids to navigation operating upon this system, of which five are
lightships. The success of the invention in the land of its origin
attracted other nations to its possibilities. At the present moment
over 700 lights, scattered throughout the world, are working upon this
principle.
If a beacon throws a fixed light, unless it is of extreme power, it is
liable to be confused with a ship’s mast-light, a fact which was found
to be one of the greatest objections to the fixed white light of the
acetylene aid to navigation. On the other hand, a flashing warning must
be of such a character that it cannot be mistaken for the twinkling
of a brilliant star, or of a light which has nothing to do with
navigation. This is where the “Aga” flasher emphasizes its value. It
throws a short, powerful gleam at brief intervals. The mariner cannot
possibly confuse or misconstrue it; the regularity of the flash arrests
his immediate attention, and its purport may be divined instantly. The
apparatus is simple and highly effective, while it has the advantage
that the periods of light and darkness can be altered in relation to
one another, or grouped, as desired.
From the maintenance point of view, however, the invention is of far
greater significance. As the gas is consumed only during the light
periods, which are very brief in comparison with the eclipse, the
economy effected is very appreciable. When the apparatus was first
brought within the range of practical application, many authorities,
which had become wedded to the oil-gas lighting system, wherein the
light flashes are of long duration in comparison with the dark periods,
maintained that the Dalén flash was too short to be of any value. They
disregarded the fact that the power of the acetylene-gas flash is about
seven times as intense as that of the oil-gas light. For instance, when
the United States acquired the first Aga light in the autumn of 1908,
the authorities demanded either a characteristic signal comprising ten
seconds of light followed by five seconds of darkness, or flashes and
eclipses of equal duration--five seconds.
[Illustration: THE “SVINBĀDAN,” UNATTENDED LIGHTSHIP IN SWEDISH WATERS.
It works upon the Dalén system with flasher, giving a flash of 0·3
second duration, followed by darkness for 2·7 seconds.]
There was a prejudice against short, powerful, and oft-repeating
flashes, mainly because their advantages were misunderstood. Practical
experience, however, demonstrated the fact that the period of light
might be reduced very considerably, and, as a result of prolonged
investigations, the Swedish Board of Pilotage adopted a characteristic
comprising 0·3 second light followed by darkness for 2·7 seconds. This
has become known since as the “one-tenth flash,” owing to the luminous
interval occupying one-tenth of the combined period of light and
darkness. It will be seen that, as a result of this arrangement, twenty
flashes are thrown per minute.
As the flame is lighted for only one-tenth of the signal period,
it will be seen that the saving of gas amounts to 90 per cent., as
compared with the light which is burning constantly. Accordingly, the
gas charge will last ten times as long with the flashing apparatus;
consequently, the accumulator need have only one-tenth of the capacity
of that for a similar beacon which burns constantly. The economy really
is not quite 90 per cent., as a certain volume of gas is consumed by
the pilot flame, which ignites the charge of gas issuing from the
flasher burner. This, however, is an insignificant item, inasmuch as
the quantity of gas burned by the pilot light does not exceed one-third
of a cubic foot per twenty-four hours.
Not only has this highly ingenious system been adapted to varying types
of buoys, similar in design and range of action to those described in
connection with the Willson apparatus, wherein the light may be left
unattended for as long as twelve months, according to the capacity of
the accumulator, but it has also been applied to “light-boats” and
light-vessels. The “light-boat” is a hybrid, being a combination of the
buoy and the lightship, and was devised to meet special conditions.
Thus, the “Gerholmen” light-boat stationed in the mouth of a Swedish
river, where the current runs exceedingly strongly, resembles a small
boat with a water-tight deck. From the centre of this rises a steel
tripod, at the top of which the lantern is placed. The gas accumulators
are stored within the hull, and are of sufficient capacity to maintain
the light for a round twelvemonth without attention, as the flashing
apparatus is incorporated.
The Aga light has come to be regarded as one of the greatest
developments in lighthouse engineering, and has been adopted
extensively throughout the world in connection with either floating
or fixed aids to navigation. The United States have decided to adopt
the system exclusively henceforth, until a further progressive step is
achieved, and several floating lights of this type have been acquired
already to guard wild and lonely stretches of the coastline.
Here and there attempts have been made to apply electricity to
inaccessible lights. The most interesting endeavour in this direction
was in connection with the lighting of the Gedney Channel from the
open Atlantic to New York harbour. This formerly constituted the only
available highway for the big liners, and it is exceedingly tortuous
and treacherous--so much so that vessels arriving off Sandy Hook
in waning daylight invariably anchored and awaited the dawn before
resuming the journey. The great difficulty in connection with Gedney’s
Channel was the distance of the main lights on shore, the direct range
at one part being over thirteen miles. Consequently the land lights
were of little utility to the pilot.
The authorities decided to convert the channel into an electric-lighted
waterway. Buoys were laid down on either side of the thoroughfare. They
were of the spar type, resembling decapitated masts projecting from
the water, and were held in position by mushroom anchors, weighing
4,000 pounds, or nearly 2 tons, apiece. Each buoy was crowned with
a 100 candle-power incandescent electric lamp, encased within a
special globe having a diameter of 5 inches. An electric cable was
laid on either side of this street and connected with each buoy. The
first section was completed in 1888, the electric gleams being shed
for the first time on November 7 of that year. The system appeared
to give such complete satisfaction that it was extended. Altogether
six and a quarter miles of cable were laid down, which in itself was
no easy feat, while prodigious difficulties were experienced in its
maintenance, owing to the severity of the currents and the treacherous
character of the sea-bed. The lights were controlled from a central
point ashore, and the idea of being able to switch on and off a chain
of aids to navigation by a simple movement presented many attractive
features. Although navigation appreciated this improvement, the Great
White Waterway did not prove a complete success. It did not possess
that vital element of complete reliability which is so essential to
navigation.
Compressed oil-gas has been employed extensively for unattended
floating lights, but it possesses so many shortcomings that it is being
superseded on all sides by acetylene, with the exception of one or two
countries which appear to be inseparably wedded to this principle. It
is expensive both to install and to maintain, while the “radius of
action”--otherwise, the period during which it may be left without
human attention--is unavoidably brief. For temporary purposes, such as
the indication of a submerged wreck, it is efficient, while it is also
serviceable for accessible positions, but it is not regarded as being
a satisfactory system for places which human hands cannot reach for
months at a time.
Crude petroleum in conjunction with the Wigham long-burning petroleum
lamp, wherein the flame is produced from a moving wick, has been
adopted widely. Lights installed upon this principle may be left for
ninety-three days at a time without anxiety. In many instances the
Wigham light is mounted upon steel boats; in other cases it is attached
to floating wooden structures. The British Admiralty in particular is
partial to this type of light, and it must be confessed that it has
proved highly serviceable and reliable.
I have described already the general principles and features of this
system. When it is applied to a floating beacon, and it is desired
to save the oil dropping from the drip valve, a tank is fixed to the
deck of the floating structure, and connected by a flexible pipe to
the coupling at the bottom of the float cylinder. A universal joint is
attached to the connection on the top of the tank to prevent the pipe
being twisted by the swinging and swaying motion of the lamp on the
gimbals. When the lamp is inspected, the oil may be pumped out of the
tank, strained, and used time after time in the float cylinder.
One of the most interesting of this type of floating boat-lights is
to be seen in Queenstown harbour. The hull is 30 feet in length, and
has a beam of 11 feet. On this, within a conical structure measuring
7½ feet high and 6½ feet in diameter at the deck, is mounted the
lantern. Although the lamp is exposed to drenching seas and heavy
storms, it has never yet failed, a fact which conclusively points to
its efficiency. It rides well, and the lamp is kept much drier than the
lights on ordinary buoys, according to the observations of the engineer
responsible for its maintenance. In this case the focus of the light is
brought 12 feet above the level of the sea.
Probably the most compelling illustration of the utility of the
automatic beacon is offered by the unattended lightship. The Otter Rock
vessel is one of the most interesting examples of this development.
It was designed by Messrs. D. and C. Stevenson, and comprises a
substantial steel hull, the deck of which is covered so that the
interior is absolutely water-tight. The craft is provided with a
central and heavy bilge keels, so as to reduce rolling to the minimum.
Two heavy steel bulkheads divide the craft into three water-tight
compartments, in the centre of which two large welded-steel gas tanks
are stowed. These are of sufficient capacity to feed the light for
several months without replenishment. The light is mounted upon a steel
tower placed amidships, which brings the focal plane 25 feet above the
water. The gas is fed from the tanks to the lantern through the tower,
a valve reducing the pressure, while a ladder enables the attendants
to climb to the lantern gallery to adjust the burner and flame, and to
clean the lenses, upon the occasion of their periodical visits.
The gas cylinders are charged from the supply-ship through flexible
hoses, the gas being compressed to about 180 pounds per square inch.
The light is of sufficient power and elevation to be seen from a
distance of some twelve miles. The beacon gives not only a visual, but
also an audible warning. On the deck of the boat a bell is mounted,
this being rung not only by the motion of the ship, in the manner of
a bell-buoy, but also by the gas on its passage from the tanks to the
lantern, the bell being fitted with two clappers for this purpose. The
gas in passing from the tank enters a receptacle having a flexible
diaphragm, which, as it becomes filled with gas, is naturally pressed
outwards. On this is mounted a central metal piece, which is connected
to a rod and lever. As the diaphragm is forced outwards, it moves the
rod and actuates the lever, which, when the diaphragm falls, return
to their normal positions. Attached to this mechanical arrangement
is the bell-clapper, which alternately is lifted and dropped upon
the dome of the bell, thereby causing it to ring. After the gas has
performed its duty in raising the clapper lever and rod, it passes
to the lantern to be consumed. Thus, while the light gleams brightly
and steadily, the bell rings with unerring regularity--about three
times per minute--day and night for months on a single charge; both
must continue in operation until the supply of gas is expended. The
success of this interesting and novel lightship has been responsible
for similar installations in other similarly wild and exposed positions
where approach is uncertain and often impossible for weeks at a time.
[Illustration:
_Photo by permission of Messrs. Edmondsons Ltd., Dublin._
THE LANTERN USED IN THE WIGHAM AUTOMATIC PETROLEUM BEACON.
The circular shallow reservoir contains the burning-oil, which feeds
the wick as it moves towards the burner, and also acts as a deck on
which the lantern is built. In this ingenious system the flame is not
produced at the end of the wick as in the ordinary lamp, but from the
flat side of the wick, which is moved continuously in a horizontal
direction over a small roller. By this means a light of uniform
intensity is obtained, as carbonization cannot occur.]
One misadventure befell the Otter Rock light-vessel, which is moored in
an open position over the rock of that name near Islay, although it was
not the fault of either the system or the designing engineers. There
was a flaw in one of the shackles, and while the ship was sawing and
tugging at her anchors during a heavy gale the flaw asserted itself,
the shackle broke, and the lightship got away. She was recovered with
some difficulty, after having drifted about twenty miles. She was found
stove in, having embraced the rocks during her wayward journey, but
otherwise was unharmed. She was towed into port, repaired, and then
taken back to her station, where she was secured more firmly than ever,
while her chains were closely inspected to make assurance doubly sure.
No repetition of the accident has occurred since, and the Otter Rock
lightship, tethered firmly to the rock, rides gales and calms, throwing
her welcome rays and droning her musical warning the whole year
round as steadily and efficiently as if she had a crew aboard.
A similar lightship was built for the Trinity House authorities from
the designs of their engineer, Sir Thomas Matthews, for service on the
English coast. This boat, built of steel, measures 65 feet in length,
by 18½ feet beam and 10½ feet depth, with the lantern carried at the
point of an open steel pyramidal structure, rising sufficiently high
above the boat’s deck amidships to bring the focal plane 26 feet above
the level of the water, thereby giving it a visible range of some ten
miles. The boat is provided with two holds, in which the gas reservoirs
are placed, the total gas capacity being about 1,500 cubic feet--enough
to keep the light burning for one hundred days.
This light is of the revolving type, and the rotation of the apparatus
is accomplished very ingeniously. Before the gas passes to the burner,
it drives a tiny three-cylinder engine, the crank-shaft of which is
connected to the revolving apparatus through gearing. The speed of the
turntable is kept constant by the aid of a governor, and the apparatus
works so smoothly and perfectly that there is not the slightest
divergence from the rate at which the apparatus is set. As the gas
emerges from the engine, it passes to the burner to be consumed. By
means of a novel apparatus, should anything befall the little motor or
the rotating mechanism, the light does not drop out of service. In that
event the gas flows directly to the burner, the only difference being
that a fixed instead of a revolving light is emitted.
[Illustration:
_By permission of Messrs. Edmondsons Ltd., Dublin._
THE “6-BAR” FLOATING AUTOMATIC WIGHAM LIGHT IN PORTSMOUTH HARBOUR.
This beacon, burning crude petroleum, burns for thirty days on a single
oil charge.]
When the Scandinavian liner _Norge_, while on her way to the United
States in July, 1904, fouled the terrible Rockall and lost 750 of her
passengers, the outcry about the absence of all means of indicating
this spot to the navigator vibrated round the world. Yet it was a
useless agitation. Rockall is a no-man’s land; no nation has planted
its flag upon its cone of granite; no Power cares whether it continues
its harvest of human lives or otherwise. The various countries appear
to think that it is too much off the map to be worthy of a moment’s
thought; its existence is brought home only by a holocaust.
After this heartrending disaster, Messrs. D. and C. Stevenson
adumbrated a promising means of indicating this awful graveyard to
the seafarer. They suggested that two automatic unattended lightships
should be constructed, and that one should relieve the other every six
months. The project was eminently practicable, but every country seemed
to shirk responsibility in the expense of its adoption. But Rockall is
a unique danger spot; in no other part of the known world does such a
formidable isolated peak of granite rise from the ocean depths, for
it is in mid-Atlantic, 160 miles west of St. Kilda, and 290 miles off
the Scottish mainland. It may be away from the great steamship lanes
of the Atlantic, yet a vast volume of shipping passes within sight
of its curious formation. Seeing that the foremost maritime Powers
defray between them the cost of maintaining the light off Cape Spartel,
surely the dictates of humanity are sufficiently pressing to secure the
indication of this islet. The maintenance of an unattended automatic
beacon, such as Messrs. Stevenson advocated, would not impose a severe
strain upon the treasuries of the leading Powers of the world, whose
interests are associated intimately with the North Atlantic.
The perfection of the unattended lightship, working automatically, has
provided the lighthouse engineer with a powerful weapon for marking the
most exposed and out-of-the-way danger spots. When the new development
is carried to its uttermost lengths, no graveyard of the ocean, no
matter how remote and inaccessible, need be without means of warning
shipping of its whereabouts.