THE BREAKWATER.
Breakwaters, Ancient and Modern—Origin and History of that at
Cherbourg—Stones Sunk in Wooden Cones—Partial Failure of the
Plan—Millions of Tons dropped to the Bottom—The Breakwater
Temporarily Abandoned—Completed by Napoleon III.—A Port Bristling
with Guns—Rennie’s Plymouth Breakwater—Ingenious Mode of
Depositing the Stones—Lessons of the Sea—The Waves the Best
Workmen—Completion of the Work—Grand Double Breakwater at
Portland—The English Cherbourg—A Magnificent Piece of
Engineering—Utilisation of Otherwise Worthless Stone—900 Convicts
at Work—The Great Fortifications—The Verne—Gibraltar at Home—A
Gigantic Fosse—Portland almost Impregnable—Breakwaters Elsewhere.
A breakwater, we are told on the highest authority, is an obstruction of
wood, stone, or other material, as a boom or raft of wood, sunken vessels,
&c., placed before the entrance of a port or harbour, or any projection
from the land into the sea, as a mole, pier, or jetty, so situated as to
break the force of the waves and prevent damage to shipping lying at
anchor within them. Thus the piers of the ancient Piræus and of Rhodes;
the moles of Venice, Naples, Genoa, and Castellamare; the piers of
Ramsgate, Margate, Folkestone, Howth, and the famous wooden dike thrown
across the port of Rochelle. The term, of late years, has been almost
exclusively applied to insulated dikes of stone. Of this description of
dike for creating an artificial harbour on a grand scale, Cherbourg,
Plymouth, and Portland present leading examples. The former, already
mentioned in this work, claims our attention.
The French, happily our good friends to-day, were not always so, and there
was a period when the splendid natural harbours, bays, and roadsteads of
this country were a source of annoyance to them. While nature had been
more than kind to us, their coast presented a series of sandy shores,
intermingled with iron-bound coasts, bristling with rocks. De Vauban, the
great engineer, was employed by Louis, the _Grand Monarque_, to inspect
the Channel shores of France, and his natural sagacity and great knowledge
caused him at once to select Cherbourg as one of the best points for
forming an artificial harbour, protected by suitable fortifications. Other
engineers recommended the same port, and one, M. de la Bretonnière,
proposed that a number of old ships should be loaded with stones and sunk,
while a large quantity of stone should be also thrown around them to form
a grand breakwater, which should rise fifty feet from the bottom. This
idea was abandoned, as it appears, partly from the fact that France had
not old vessels enough to spare for the purpose, and that it would cost
too much to purchase them from foreign nations.
In 1781 an eminent French engineer proposed that, instead of one
continuous breakwater, a number of large masses or congregations of
stones, separated from each other on the surfaces but touching at the
bases, should be built on the sea bottom, believing that they would break
the force of the waves almost equally well. As a part of his plan he
suggested that they should be sunk in large conical _caissons_ of wood,
150 feet in diameter at the base and sixty feet broad at the top. These
wooden cones were practically to bind and keep the stones together. They
were to be floated to the site with a number of empty casks attached as
floats, then detached, filled with stones, and sunk. An experiment at
Havre having been considered satisfactory, the Government accepted the
idea, and ordered that operations should be immediately commenced at
Cherbourg. A permanent council was appointed, as were officers and
engineers. In 1783 barracks and a navy-yard were built, and at Becquet, a
short distance from Cherbourg, an artificial harbour, capable of holding
eighty small vessels for the transport of the stone, was literally dug
out.
On June 6th, 1784, the first cone was floated to its destination, and a
month later a second was similarly conveyed, in the presence of 10,000
spectators. Before the latter could be filled with stones a storm, which
lasted five days, half demolished it. In the course of the summer and
autumn not less than 65,000 tons of stone were deposited in and around the
cones. In 1785 several more cones were completed and sunk; at the end of
the year the quantity of stone deposited amounted to a quarter of a
million tons, and at the end of 1787 a million tons. At the end of 1790,
when the works had been seven years in progress and the Government was
getting very tired of the whole matter, between five and six million tons
of stone had been dropped into the sea. M. de Cessart, the engineer, found
that, in order to sink five cones per annum, he had to employ 250
carpenters, 30 blacksmiths, 200 stone-hewers, and 200 masons.
One could hardly expect much permanency from a wooden covering sunk into
the sea, and it is not surprising that, one by one, they burst, few
lasting more than a year. The outbreak of the Revolution put an end, for
some time, to the operations at Cherbourg.
When the construction of the Cherbourg breakwater was resumed, the wooden
cone system was abandoned, and the stone was simply sunk from vessels of
peculiar construction. The breakwater was completed under Napoleon III.,
at a cost exceeding two and a half million pounds sterling. The actual
breakwater itself was finished in 1853,(61) but since that time most
important fortifications have been constructed on the upper works. This is
the greatest breakwater in the world, its length being nearly two and a
half miles; it is 300 feet wide at the base and 31 at the top. The
water-space shut in and protected is about 2,000 acres, much of this great
area being, however, too shallow for very large vessels.
Taken in connection with the fortifications, this breakwater has a value
greater than any other in the world. At the apex of the angle formed by
the junction of the two branches of the breakwater there is a grand fort,
and it bristles generally with batteries and forts, as indeed does
Cherbourg generally. Dr. W. H. Russell wrote of it, in our leading journal
in 1860 that, “Wherever you look you fancy that on the spot you occupy are
specially pointed dozens of the dull black eyes from their rigid lids of
stone.” With its twenty-four regular forts and redoubts, not including
those on the mole, floating harbours, building slips, navy-yards,
arsenals, and barracks, Cherbourg is a most formidable place.
[Illustration: CHERBOURG, FROM THE SEA.]
In England Rennie’s great Plymouth breakwater is the most remarkable
specimen, among many others. Its dimensions are not as great as that of
Cherbourg, but it was, nevertheless, a vast undertaking. It consists of an
immense number of blocks of stone thrown into the Sound, and forms a
barrier nearly a mile in length above the surface of the water. This grand
work was commenced in 1812, and by the end of the second year about 800
yards of the breakwater began to appear at low water, and the swell was so
much broken that ships of all sizes began to take shelter behind it; while
the fishermen within its shelter could not judge accurately of the weather
outside the Sound, so great was the change. Several limestone quarries
near the Catwater were purchased of the Duke of Bedford for £10,000, and
some fifteen vessels were constantly employed in removing the blocks,
which ranged in weight from one to ten tons. These vessels were of
ingenious construction; they had two railways laid along them parallel to
each other, with openings in the stern to admit the cars or trucks laden
with stones. These were wheeled from the quarry to the quay, and so on to
the vessels, till the lines of rails were filled with trucks. The vessels
then proceeded to the works, each bearing its load of stone-laden trucks.
On reaching the breakwater each truck was wheeled to the opening, and the
stones tipped into the sea. During the first five years the amount of
stone deposited gradually rose from 16,000 to 300,000 tons per annum. The
large masses were first lowered, and then smaller stones, quarry rubbish,
&c., to fill up the interstices. The structure was completed in 1841, with
the use of 3,670,444 tons of stone(62) and at a cost of something like a
million and a half of money. A distinguished French engineer, M. Dupin,
who visited the works during their progress, describes in glowing terms
the admirable arrangements, the order and regularity visible in all the
proceedings. “Those enormous masses of stone,” he remarks, “which the
quarrymen strike with heavy strokes of their hammers; and those aerial
roads of flying bridges, which serve for the removal of the superstratum
of earth; those lines of cranes, all at work at the same moment; the
trucks, all in motion; the arrival, the loading, and the departure of the
vessels, all this forms one of the most imposing sights that can strike a
friend to the great works of art. At fixed hours the sound of a bell is
heard, in order to announce the blasting of the quarry. The operations
instantly cease on all sides; all becomes silence and solitude. This
universal silence renders still more imposing the noise of the explosion,
the splitting of the rocks, their ponderous fall, and the prolonged sound
of the echoes.”
“The waves,” said Rennie, “were the best workmen” in the construction of a
breakwater of rough stones, and on the whole his belief was confirmed, for
the storms by which his great work was assailed rather helped than
hindered it, by showing the most desirable slope on the sea-side, while
comparatively little damage was done. The slope of the stone barrier was,
however, by their force changed very greatly. An inclination of three to
one was altered to about five to one, and Rennie had recommended that the
authorities should take a lesson from nature and finish the breakwater
according to her teachings. “It would appear,” says Mr. Smiles,(63) “that
Mr. Whidbey, the resident engineer, contrived to finish most of the
exterior face at a slope of only three to one, as before; and that it
stood without any material interruption until several years after Mr.
Rennie’s death. By that time nearly the whole of the intended rubble,
amounting to 2,381,321 tons, had been deposited, and the main arm, with
200 yards of the west arm, making 1,241 yards in length, had been raised
to the required level. The work had arrived at that stage when it had to
experience the full force of another terrific storm, which took place on
the 23rd of November, 1824. It blew at first from the south-south-east and
then veered round to the south-west, and the effect of this concurrence of
winds was to heap together the waters of the Channel between Bolt Head and
Lizard Point, and drive them, with terrific force, into the narrow inlet
of Plymouth Sound. This storm was not only greatly more violent, but of
much longer duration than that of 1817. When the breakwater could be
examined it was found that out of the 1,241 yards of the upper part, which
had been completed with a slope of three to one, 796 yards had been
altered as in the previous storm, and the immense blocks of stone which
formed the seaface of the work had, by the force of the waves, been rolled
over to the landward sides thus reducing the sea-slope, as before, to
about five to one. The accuracy of Mr. Rennie’s view as to the proper
slope—which was indicated by the action of the sea itself—was thus a
second time confirmed;” and a board of eminent engineers reporting in
accordance, the work was so finished. When the action of the sea had
formed its own slope and had wedged together and settled the great mass of
materials which form the breakwater, and when no further movement was
apparent, but the whole appeared consolidated together, then the slope
towards the sea was cased with regular courses of masonry, dove-tailed and
cramped together, the diving-bell being brought into requisition for
placing the lower courses. A lighthouse has been erected on its western
extremity, and the work may be regarded as a magnificent success, worthy
of a great maritime nation.
A third leading illustration of a magnificent breakwater is afforded at
Portland, and it is deserving of particular mention inasmuch as all
authorities agree that it was constructed with little or no waste of the
public money. “In the mind of the inquiring tax-payer,” said our leading
journal,(64) “breakwaters are always associated with millions of money
thrown broadcast into the sea, in out-of-the-way bays and inlets, which
even without these obstacles to make them more dangerous, the most
distressed mariner would be particularly careful to avoid;” and the writer
goes on to mention several which either ought not to have been attempted,
or where extravagant expenditure has been incurred. “In such a woeful list
of hideous failure and costly mismanagement, it is a comfort to perceive
that the long lane begins to turn at last, and that from our now having
one good standard to go by, we may hope for better things for the future.
Portland breakwater is a really grand and magnificent work, and one of
which the nation may well be proud if it is inclined to let bygones be
bygones, and forget the many successive failures before it was able to
attain so much.” Portland breakwater is the right construction in the
right place, and before its erection the Roads afforded doubtful shelter
to vessels in distress. One advantage it enjoys, that of possessing a
splendid anchorage of stiff blue clay, and being free from rock or shoal
from the island of Portland itself up to the very esplanade of Weymouth.
There, too, was the stone on the very spot; steep and rugged heights for
fortifications, a noble harbour for shipping, and rail communication with
all parts. But all these advantages might have been ignored but for the
formidable nature of the works constructed at Cherbourg. The port itself
is about five hours’ steaming from the French Cronstadt it was designed,
_sub rosâ_, to keep an eye upon. So, in 1844, the commissioners
recommended that it should be made a grand fortified naval station. In
1847 an Act was passed authorising the construction of a breakwater, and
in 1849 the foundation-stone was laid by the Prince Consort.
[Illustration: PORTLAND.]
Nature has provided, in the mighty bank known as the Chesil Beach,
practically a great shingle embankment, protection to Portland Harbour on
the west and south-west, and the object of the breakwater was to secure,
by engineering art, a similar protection to the bay on the south-east
side. The Chesil Bank, though now and for long perfectly impregnable to
the tremendous rollers of the south-westerly gales, was not always so, and
as late as the reign of Henry VIII, great breaches had been temporarily
effected by the power of the sea. Still it affords a splendid protection,
as does now the mighty double breakwater designed by Rendel, and brought
to completion by Coode. The breakwater leaves the shore at the
north-eastern extremity of the island, and runs out due east to a distance
of 600 yards. “This inner limb alone,” wrote an authority in
engineering,(65) “is a splendid achievement of human labour and skill. It
has been top-finished by a grand superstructure of hewn granite, and ends
in a circular head, which has been completed as a fort and mounts eight
guns. The foundations of this massive bastion have been most carefully
planned, with especial reference to the safe passage of the largest
vessels through the 400 feet gap which the fort flanks on one side. The
masonry is continued in a perpendicular line to a point 25 feet below the
lowest water-line of spring-tides. A ship of the line, as is well-known,
draws at the utmost 24 feet. An extra foot of perpendicular masonry,
therefore, having been allowed, the lower masses of the fort begin to
slant outwards, and continue to do so till they reach the firm clay
bottom. This lower portion consists of a well-consolidated mass of unhewn
stone. The outer, and by far the longer limb, of the breakwater begins to
bend away to a point very near due north shortly after leaving the gap,
the further side of which is also flanked by a circular head.... The whole
of this vast outer limb, with the exception of the circular head at its
inner extremity and a fort at the other end, consists of nothing more than
a stupendous bank of rough unhewn stones of all shapes and sizes, tumbled
out of the wagons on the timber staging above. Divers, constantly
employed, have effectually prevented the chance of any holes being left in
the rising mass, and have been able to indicate the precise spot over
which a given number of loads were required to be ‘tipped.’ The security
of the bank is further guaranteed by its enormous width at the base; and
although the waves have already rounded many a giant block below the
water-line and made it look as if its present place had been its abode
ever since the Creation, yet this polishing and grinding is the extent of
the effect which they will be able to produce upon a work probably
destined to hold its own as long as Portland itself.”
The rapidity with which the breakwater was constructed reflected great
credit on Mr. Coode. The actual routine of the construction followed, when
the line for the structure had been sounded and carefully marked out, was
to commence piling for the railway that was to carry the long trains of
wagons filled with the stone; and when a short piece of this was
completed, to go on “tipping in” the rubble and rough stone till they made
their appearance above water at last; then the piling was carried forward
a few yards more, and the process repeated, and so on by successive stages
to the completion of the work. All appears very simple on paper until we
learn that it had to be accomplished through eleven fathoms of rough
tumbling waves. One night’s rough weather often swept away the timber-work
that cost many thousands of pounds, and many months of labour to construct
and fix in its position in the sea. The piling that had to resist the
action of a deep and heavy sea, and to carry also, at a height of 90 feet,
a railway for the heaviest traffic, required to be something more than a
common framework of timber. Every log used had to be first of all
saturated to its very centre with creosote, and this was done in a most
ingenious manner. A great boiler, 100 feet long and 7 feet in diameter,
was filled with the largest and finest logs procurable; the mouth being
closed with a solid air-tight cover, the air was pumped out, not only from
the tube, but from the very pores of the wood itself. When the vacuum was
as complete as possible, the creosote was admitted from tanks at the
bottom and forced into the timber by hydraulic power of about 300 lbs. to
the square inch. In this the logs remained for two or three days, by which
time the creosote was forced into the fibre of the wood. Several of the
logs thus prepared were bolted and bound together, till one huge spar 90
feet long, and eight or nine tons in weight, was formed. Then an iron
“Mitchell” screw—as used in the lighthouses built on sands, already
described—was affixed at the lower end, and the whole sunk till it rested
on the bottom, when it was worked round by a capstan till it was firmly
screwed into the clay. Thus secured, they were tolerably safe, though
single heavy waves would uproot piles and moorings together, to obviate
which two or three piles were generally set at the same time, and well
bound together by powerful cross timbers.
The stone quarried for the breakwater from the very top of Portland Island
was largely excavated and brought to the spot by convict labour. The stone
itself used was unfit for architectural purposes, but quite suitable for
the breakwater. The convict prison, also on the top of the island, was
virtually the barracks for 900 labourers, who were more profitably
employed than in walking a treadmill or picking oakum. The quarries were
some 400 or 500 feet above the level of the breakwater, and the stone was
conveyed to it by three inclines of broad double gauge rails. The trains
of trucks or wagons were worked up and down with a wire rope over a drum,
the weight of the loaded descending wagons winding the empty ones up again
to the quarries. A powerful locomotive pushed the loaded trains to the end
of the work, where the stone was tipped into the sea, as much as 3,000
tons a day having been sunk at Portland. The total amount so committed to
the deep was about 5,360,000 tons, and the area protected by the
breakwater would accommodate sixty of the very largest men-of-war, and
almost any number of smaller vessels.
“During the progress of the works,” wrote Mr. Moule, “the engineer has
from time to time instituted some highly interesting investigations into
the structure of the Chesil Bank.... During a single night’s gale, between
three and four _millions of tons_ weight of pebbles have been found to be
swept away into the gulfs of the Atlantic, being gradually thrown back
again in the three or four following days. The size of the pebbles had
long been observed to vary greatly at the two opposite ends of the beach.
At the western, or Abbotsbury end, they are exceedingly small, more
resembling gravel than shingle. At the Portland end it is not uncommon to
meet with them several inches in diameter, and several pounds in weight.
This phenomenon has been explained by the very probable assumption that
the pebbles are driven eastward by the wind-waves, and not moved by the
slow and (for purposes like this) powerless tidal current. The larger
pebbles, presenting a broad surface to the waves, are easily rolled
forward, while the smaller ones are passed by, offering a less surface,
and becoming more easily imbedded in the sand.” It is said that a
practised smuggler on that coast could tell his whereabouts on the bank in
the darkest night or thickest fog, by feeling the size of the pebbles on
which he stood. And smugglers and “wreckers” were once very numerous among
the Portlanders. In these better days their courage and great personal
strength has saved many a life and ship endangered off the bank.
An old and popular song says that—
“Britannia needs no bulwarks,
No towers along the steep,”
but recent legislators have evidently not been so thoroughly satisfied of
the fact, or they would not have authorised the construction of the great
fortifications at Portland, which make it almost the Gibraltar of the
Channel. The splendid breakwater there did not need protection. All the
battering it is ever likely to get could not injure it seriously, and
whatever ruins Macaulay’s New Zealander may stand upon, they are not
likely to be those of a great breakwater, each year of the existence of
which renders it generally more compact. But it was for good reasons that
the extensive works of Portland were undertaken. “We,” said the _Times_,
“of all people in the world, who so toiled and suffered, lavishing blood
and treasure under the walls of Sebastopol, should be the last to
underrate the importance of a good fortification as a check to an invading
army.” The reader will hardly require any defence of such policy, for
naval arsenals contain the very germ of our power, as the iron safe of the
prudent man contains his valuables.
The Bill of Portland greatly resembles the situation of Gibraltar. There
are the same bold, steep, rocky headlands; the breakwater stands in place
of the Mole, and Chesil Bank connects it with the mainland, as the neutral
ground does our great Mediterranean citadel with Spanish soil. “Its
height, its isolation, and the harbour it commands, all pointed it out as
a place for an impregnable—we had almost said an inaccessible—fortress. To
the late Prince Consort is due the credit of having seen its vast
importance in this respect, as it was also owing to his enlightened
judgment that the breakwater was begun at last, and he himself laid the
foundation-stone. Portland is rising, as we have said, into a first-class
fortress, of which the Verne is the great key or citadel.” So spoke the
_Times_, in 1863; and now Portland is the best fortified port and naval
station in the kingdom.
The Verne is a height which, like La Roche at Cherbourg, dominates over
all around it for miles, especially on the side which overlooks the
breakwater and the sea. On the north side it is protected by nearly
perpendicular cliffs; elsewhere it is fully protected by art. One of its
greatest defences is the dry ditch which completely encircles the whole
work, except on the north side just mentioned, where it is both
unnecessary and impossible. This ditch is one of the greatest ever
undertaken in ancient or modern days. Its depth is 80 feet, and its width
100, and in some places 200 feet; its length is nearly a mile, and its
floor is 368 feet up the hill-side. Nearly two million tons of stone had
to be blasted to form it; and it would never have been excavated on the
colossal scale indicated, but that all the said stone was utilised in
building the breakwater. With this tremendous artificial ravine to cross,
with fortifications and bastions fully prepared with heavy Armstrong
ordnance towering above, what enemy is ever likely to attack the citadel
of the Verne? Our leading journal spoke of it as more compact than
Cherbourg, Cronstadt, or Sebastopol, while it is more than three times
their elevation above the sea.
Jutting out from the main fortress are two bastionettes, one of which has
eight faces, mounting guns on each so as to sweep with a murderous fire
two-thirds of the whole length of the fosse or ditch. The other is nearly
as formidable, and both are pierced with loop-holes in all directions for
the fire of riflemen. The great barracks in the enclosure of the Verne
can, at a pinch, accommodate 10,000 men, the peace garrison being about a
third of that number. The arrangements for water supply are perfect, great
reserve tanks having been cut from the solid rock, and covered with
shot-proof roofs. These are kept full, and, protected from air and light;
the water is always sweet. Portland bristles with batteries; but the Verne
commands everything in range of cannon, inside or outside the breakwater,
including all parts of the island, and can cross fire with other important
forts. It is probably the strongest fortified harbour in the world.
[Illustration: HOLYHEAD BREAKWATER.]
Other and important breakwaters, like that of Holyhead, which cost a
couple of million sterling, and which is generally cited as an example of
much money thrown into the sea; Alderney, which has swallowed up close on
three-fourths of the above sum; and Dover, which has a fine _vertical_
sea-wall, might be mentioned. Enough has been said to show the general
importance of the subject to a maritime people, and that, on the whole,
England has been fully alive to the fact. Indeed, counting large and small
breakwaters and sea-walls, more has been expended in this country for
these works than in any two or three foreign countries possessing
sea-boards.