THE BROOKLYN BRIDGE
Harper's Monthly, 1883
PEOPLE who seventeen years ago divided an amphibious existence
between New York and Brooklyn will long remember their arctic
voyages in the East River during the severe winter of 1866-7.
There were days in that season when passengers from New York to
Albany arrived earlier than those who set out the same morning
from their breakfast tables in Brooklyn for their desks in New
York. The newspapers were filled for weeks with reports of the
ice gorges, and with vehement demand for and discussion of the
bridge, which all agreed must be built at once from New York to
Brooklyn.
Public feeling was soon highly gratified by the announcement
that leading citizens of Brooklyn were moving in the matter, and
that a bill for chartering the New York Bridge Company had been
introduced into the Legislature then in session at Albany. The
popular excitement gave but a timely lift to a movement already
ripe, and to a charter already placed before members of the Legislature
and government of the State, months in advance of the session,
while the waters of the East River were sparkling in the warm
sunshine as if ice gorges were never to be known. As early as
1865 Mr. William C. Kingsley, of Brooklyn, of whom the public
has since heard much in connection with this enterprise, had employed
an eminent engineer to draw a plan and make estimates for a suspension
bridge very nearly in the location ultimately fixed for the present
work.
The charter originally and provisionally fixed the capital
at $5,000,000 (with power of increase), and gave the cities of
New York and Brooklyn authority to subscribe to the capital stock
of the company such amount as their Common Councils respectively
should determine. This latter was in effect a sort of "caution
money," or a guarantee of the sound interest which those
who were to govern the work ought to take in it, for it was wisely
judged that neither private capital nor municipal management could
be relied on to carry such a work successfully to completion.
Public credit must be joined with private enterprise, in the hands
of men who had too much at stake in the work to permit it to be
perverted to political purposes.
But by the time the foundations of the towersthe chief
difficulty to be overcomehad been successfully completed,
popular jealousy of a company enjoying the control of so much
public expenditure began to make itself felt in various ways,
and to serve as the instrument of various personal and political
rivalries and enmities. At the same time, the work was so well
advanced, and its plans and methods so firmly fixed by what had
already been done, that its friends now felt prepared to resign
the great enterprise entirely to the two cities (acting through
a commission or board of trustees, appointed half by the Mayor
and Comptroller of each city, and including those officials),
and prepared a bill to that effect, which was approved by the
Legislature and accepted by the city governments. Under the charter
thus amended, the bridge is public property, 662/3
per cent. to be paid for and owned by the city of Brooklyn and
331/3 per cent. by the city of New York,
the actual payments by the private stockholders having been reimbursed
and their title extinguished. The engineers, etc., as well as
the principal working members of the directory, retained their
places as from the first, so that the work is, after all, a unit
from beginning to end.
On the organization
of the company, in May, 1867, one month after the passage of the
incorporating act, John A. Roebling was appointed engineer (May
23,1867), and he made his report of surveys, plans, and estimates
on the 1st of the following September. In March, 1869, a board
of consulting engineers was convened at the request of Mr. Roebling
to examine his plans, and also to report upon the feasibility
of the work. In the following May a commission of three United
States engineers was appointed by the War Department to report
upon the general feasibility of the project, and particularly
as to whether or not the bridge would be an obstruction to navigation.
The plans of Mr. Roebling were fully endorsed by both boards of
engineers, the government commission recommending however, an
increase of five feet in height. The work of preparing the site
of the foundation of the Brooklyn tower was commenced January
3,1870, but Mr. Roebling did not live to see the first stone laid
in the magnificent structure that was to crown his illustrious
career. In the summer of 1869, while engaged in fixing the location
of the Brooklyn tower, a ferry-boat entering the slip thrust the
timbers on which be stood in such a manner as to catch and crush
his foot. The injury resulted in lock-jaw, from which be died
sixteen days after.
A fit successor was found in his son, Washington A. Roebling,
who had not only been the accomplished associate of his father
in some of his principal works, but had aided him most efficiently
in the preparation of the designs and plans of the bridge. We
say a fit successor was found, for at this time, when the grandest
monument of engineering skill the world has ever seen is practically
completed, certainly no other testimony is needed as to the great
engineering ability and preeminent fitness of the younger Roebling
to direct such a great undertaking. During the fire in the Brooklyn
caisson in December, 1871, Mr. Roebling became himself a victim
to the "caisson disease," but even from his sick-room
his oversight of the work has not flagged.
Before the actual work of construction had commenced, however,
it became apparent that in order to more perfectly adapt the structure
to its intended uses, and to make ample provision for the rapidly
increasing volume of inter-urban commerce consequent upon the
development and growth of the cities, considerable modification
must be made in the original design. The changes were, of course,
in the direction of not only a larger and more capacious structure,
but also of increased solidity and strength throughout. Such changes
involved a very considerable addition to the cost. Mr. John A.
Roebling originally estimated the cost of the bridge at $7,000,000,
exclusive of the land required, which has cost about $3,800,000,
and the time of building at about five years. The actual cost
of the bridge, when completed, will be about $15,500,000, which,
as compared with the original estimate of $10,800,000, shows an
increase in cost of nearly $5,000,000. The items of additional
cost are as follows: First, the United States government required
an increase of five feet in height, making the clearance under
the centre of the bridge 135 feet. At the same time it was decided
to widen the bridge from 80 to 85 feet. These changes involved
an increase of 8 per cent. in the cost of the entire bridge, including
superstructure, towers, foundations, and anchorages. Second, the
amount set apart for building the foundations of the towers in
the original estimate was found to be entirely inadequate. For
the New York tower a pile foundation was originally intended,
whereas it was found necessary to go down 78 feet to the bedrock,
and the cost of labor in compressed air at such unprecedented
depths proved to be four and a half times as much as was anticipated,
as was also that of excavating the hard conglomerate under the
Brooklyn tower. Third, steel was substituted for iron as the material
to be used in the construction of both the cables and the suspended
superstructure, thereby vastly increasing the strength of all
the parts. The items thus far enumerated foot up nearly two millions,
which covers the excess in cost on the bridge proper. In his original
plan and estimate, Mr. John A. Roebling contemplated approaches
constructed of light iron girders, or trestle-work, supported
by pillars of brick or stone, but it was concluded to build entirely
of granite and bricka change that has resulted in one of
the finest masonry viaducts in the world. This involved an increased
expenditure of about one and a half millions. The archways have
been constructed with a view to their utilization as warehouses,
and $400,000 has been set apart by the trustees for the placing
of fronts and floors in them. As Mr. Roebling in his original
report says, the cost of these improvements should not be charged
in that of the bridge, and it was accordingly omitted by him.
Then there are the station buildings and the elevated railway
structures that are now building on the approaches, making a connection
of the system of rapid transit of New York with that of Brooklyn
when it shall have been built. Of course this was not originally
contemplated, and it has swelled the cost of the bridge by nearly
half a million. Finally, there is a comprehensive item which could
not have been anticipated, but which would be underestimated at
half a million, namely, the preliminary expenditures, general
superintendence, interest and discount on city bonds, and expenses
legal, medical, funereal, and prandial. These additions to the
cost, however, would never have swelled to so large an amount
if it had not been for the needless and costly delays caused by
the failure of the city of New York to promptly provide its proportion
of the necessary funds. That this has caused an enormous increase
in the cost of the bridge is well known, but it would be difficult
to name an amount. The land expenses will be largely redeemed
by the rentals the cities will receive from the warehouses under
the approaches.
The principal ferry to Brooklyn takes a diagonal course up
stream to a point determined by the abrupt falling off of the
heights near Fulton Street. The bridge takes its Brooklyn departure
in obedience to the same topographical consideration. Its course
is a straight line drawn from near the junction of Fulton and
Main streets, Brooklyn, to the terminus fixed upon in New York,
on Chatham Street, opposite the City Hall. This line and terminus
were fixed upon as the result of Mr. Roebling's exhaustive examination
and discussion of the question in his first report, of September
1, 1867, and no reason has been found to modify or to question
the wisdom of his conclusions.
This line strikes the river at its eastern or Brooklyn shore
close alongside of the north slip of Fulton Ferry. Its course
across the river is not exactly at right angles to the shore,
but makes a little down stream, striking the New York side at
the foot of Roosevelt Streetfour blocks further up stream,
however, than the still more oblique ferry route. Here, then,
are four points defined in a straight line: the two ends, and
the two points at the water line, 1595½ feet apart, to
be connected by the bridge proper with a single span. Three points
in the air line of the bridge are also determined: the central
altitude of 135 feet above mean high water required by the United
States government, and the two terminal elevations, in New York
and Brooklyn respectively, of 38.27 and 61.32 feet above high-water
mark. The rise from these two to the central altitude gives the
line of the bridge a gentle upward curve from either end to the
centre, where it will be fifteen feet higher than at the towers,
and forty-six feet higher than at the anchorages.
The adoption of a suspended span of 1595½ feet, at a
height of 135 feet, also determined (in combination with other
mathematical and mechanical considerations) the height of the
towers (2762/3 feet) from which the span
must be suspended, and two other points in the air line of the
bridge, at which the ends of the suspension cables are securedin
other words, the anchoragesfor the cables are not to pull
on the tops of the tall towers, but to rest on them with nearly
a simple vertical pressure, being not even fastened; and thus,
so far from tending to pull the towers over, the suspended weight
tends only to hold them in position. The cables are therefore
anchored inland, at a distance of 930 feet back from the towers
on each side.
The anchorages are solid cubical structures of stone masonry,
measuring 119 by 132 feet at the base, and rising some 90 feet
above high-water mark. Their weight is about 60,000 tons each,
which is utilized to resist the pull of the cables. The mode of
anchoring the cables will be described in its proper place. Suffice
it for the present to conceive them thus anchored by their extremities
on each side the river 930 feet back from the towers, and at the
water-line on each side lifted up with a long, lofty, and graceful
sweep over the top of a tower 276 feet high, and drooping between
the two towers in a majestic curve which one can liken to nothing
else for grandeur but the inverted arch of the rainbow.
Rising from the towers at an elevation of 118 feet above high-water
mark in gentle but graceful curve to the centre of the river span,
where it meets the cables at an elevation of 135 feet above high-water
mark, is the bridge floor, an immense steel framework bewildering
in its complexity. The framework consists essentially of two systems
of girders at right angles to each other. The principal crossbeams
or girders supporting the floor proper are light trusses thirty-three
inches deep, placed seven feet six inches apart, and to these
are attached the four steel rope suspenders from the cables. Halfway
between these principal floor beams are lighter ones, to give
additional support to the planking. To unite these cross-beams
together, and to give the proper amount of stiffness and strength
to the floor, there are six parallel trusses extending along the
entire length of the bridge. The floor beams are further united
together by small longitudinal trusses extending from one to the
other, which, together with a complete system of diagonal braces
or stays, form a longitudinal truss of eighty-six feet in breadth.
It will be seen, thus, that this combination has immense strength,
weight, and stiffness, laterally, vertically, and in every direction.
To relieve the cables in a great measure of this enormous burden,
and at the same time effectually prevent any vertical oscillations
in the bridge floor, there is a multitude of suspensory stays
of steel wire ropes diverging from the tops of the towers to points
about fifteen feet apart along the bottom of four of the vertical
trusses. These stays extend out for a distance of 400 feet from
the towers, and are of themselves capable of sustaining unaided
that portion of the great frame and its load in position. At the
towers the framework is firmly anchored down, and again confined
against the lifting or pushing force of the wind by a system of
under-stays lying in the plane of the floor, so that no conceivable
cause can ever disturb its rigid fixity of position and form.
At and near the centre of the span, however, where these stays
do not act so efficiently against any tendency to distortion,
and to still further unite and stiffen the whole system, the two
outside cables are drawn inward toward each other at the bottom
of their curves. By this means each of them presents its weight
in the form of an arch against, an oblique pressure from below
and the opposite side, and resists more or less in the same way
any force from the like directions. The two inner cables at the
same time are drawn apart at the bottom of their curves, thus
approaching each its outside neighbor, and pairing with it, so
as to combine their opposing arches against lateral forces from
either direction. The weight of the whole suspended structure
(central span), cables and all, is 6740 tons, and the maximum
weight with which the bridge can be crowded by freely moving passengers,
vehicles, and cars is estimated at 1380 tons, making a total weight
borne by the cables and stays of 8120 tons, in the proportion
of 6920 tons by the cables and 1190 tons by the stays. The stress
(or lengthwise pull) in the cables due to the load becomes about
11,700 tons, and their ultimate strength is 49,200 tons.
The great frame, as above described, presents on its upper
side five parallel avenues of an average breadth of sixteen feet,
separated by the six vertical lines of trussing, which project
upward like so many steel fences. The outside avenues, devoted
to vehicles, are each nearly nineteen feet wide. The central avenue
has a width of fifteen and a half feet, and is elevated twelve
feet above all the others, for a footway, thus giving to the pedestrians
crossing the bridge an unobstructed view of the river. The vertical
trussing forms outside parapets eight feet high above the common
bridge floor, for the security of vehicles, etc., while the inner
lines of the same will form inner parapets to the cars and footways,
supplemented by wire netting which will break the force of the
wind. The intermediate avenues, one on each side of the footway,
will be occupied by cars, constantly and rapidly moving back and
forth from terminus to terminus by means of a stationary engine
and endless wire rope.
The great steel cables, fifteen and three-quarter
inches in diameter, are not, however, limited to supporting the
main span, but are prolonged over the tops of the towers, and
descend thence to the anchorages on the shores, at distances,
as before stated, of 930 feet. The portions of the cables suspended
from the towers to the anchorages support the shore spans of the
bridge, which are constructed precisely like the central span
already described. The anchorages are therefore the next feature
of the work to be noticed. They are structures at once exceedingly
simple and satisfactory to the mind. There is little more to imagine
than a great four-square mass of masonry, with a pair of broad
arched passages through it, partly to exclude superfluous cost,
and partly to afford convenient avenues for locomotion. The dimensions
of this mass are 90 by 119 by 132 feet, and its weight, which
is its chief importance, the inconceivable amount of 120 million
pounds. At the bottom of the structure, and near its rear side
from the bridge, are imbedded four massive anchor plates of cast
iron, one for each of the cables. These plates measure 16½
by 17½ feet on the face, and are 21 feet thick at the centre.
The weight of each plate is over 46,000 pounds. And yet it is
far from being a solid mass, which would waste perhaps half its
material in perfectly ineffective positions. On the contrary,
it is formed like a star, with many rays stretching from a massive
centre, and tapering to their extremities, where greatly reduced
strength and narrowed bearings are quite sufficient for the simple
purpose of uniting the resistance of the superincumbent masonry
upon the point of pull at the centre. This point is made by two
rows of nine parallel oblong apertures through the two and a half
feet of solid iron, and through these apertures pass eighteen
forged bars of iron, with an eye at each end. Through each of
the nine eyes matched in position as one, below the under side
of the anchor plate, passes a round iron bolt or key, which is
drawn up against the plate, fitting in a semi-cylindrical groove,
and thus the first link in the anchor chain is constructed and
made fast. The link bars average twelve and a half feet long;
and in the first three links, where the pull from the cables is
least felt, they are seven inches wide and three inches thick,
being swelled at the ends sufficiently to preserve their full
strength with eye-holes five to six inches in diameter. The bars
of the fourth, fifth, and sixth links are increased in size to
eight by three inches, and after these the size is nine by three,
with the exception of the last link, in which the number of bars
is doubled, and the thickness halved. The pins or bolts connecting
link to link are turned shafts of wrought iron five feet long
and five to seven inches in diameter.
The four great anchor plates being set in
position at the bottom of the masonry, each with the first double
ninefold link of its anchor chain made fast through its centre,
and standing erect above it, the masonry is next built over the
anchor plates, and close around the chain bars, to the height
of the latter, and extended over the whole area of the structure
to the same height. Then the second link or set of chain bars
is set, the eyes of the new nine fitting between those of the
former nine, and the heavy bolt passing through all the eighteen
eyes at once, and uniting each of the two ninefold links with
a joint like that of a hinge. Each new link after the first two
is now made to incline forward to the bridge a little more than
its predecessor, forming a regular curve, so adjusted as to bring
the chain out near the opposite (upper) corner of the structure
to that from which it started. Here the cables enter the face
of the anchor wall for about twenty-five feet, and meet the ends
of the chains. The bars of the last link number thirty-eight,
arranged in four tiers. There are nineteen strands in each cable,
and the end of each strand is here separately bent and fastened
in a loop around an eye-piece of cast iron, called a "shoe,"
having a groove in its periphery to fit the strand. The ends of
the strands are thus "eyed" like the link bars, and
fraternize with the last set of the latter, fitting between them
eye to eye, and keyed together with them by the eyebolt. The ends
of the great cables are now anchored fast with what seems to the
imagination an enormous superfluity of weight and strength. It
seems as if the cables would be torn apart ten times over by a
force that was sufficient to pluck out their monstrous spread
of iron roots from the foundations of that solid cemented mass
of rock. Undoubtedly this is true; but the intention of the engineer
is not merely to equal the strength of the cables with that of
their anchorage, but also to give the anchorage a solidity to
be absolutely unaffected in the slightest degree by the incessant
pull of loads and tug of storms for a hundred years, so that no
loosening or vibration can ever be initiated.
To make assurance fourfold sure, the metal
for this, as for every part of the work, has been tested by means
of specimen pieces under the enormous power of the hydraulic press
to its breaking point, a wide margin being always required above
the highest possible strain that it is estimated can ever come
upon it.
All this is plain work. The anchorages are far within-land.
But the great suspension towers to be connected by the central
span of the bridge must be pushed out to the extreme wharf line
in deep water, for even then the breadth of water to be bridged
at one spring is such as no engineer ever attempted beforenearly
1600 feetand not only the difficulty but the cost of the
work is increased in an enormous ratio by every foot of added
length in a single span. We have therefore before us here one
of the most interesting problems and one of the most brilliant
triumphs of engineering: to build great works of masonry up from
beneath the bed and through the rushing tides of a deep arm of
the ocean, with all the precision and cemented solidity of the
dryland anchorages we have just been viewing. This part of the
work, therefore, was first in order: this achieved left nothing
problematical, whether as to availability or cost, in the remainder
of the work.
Probably to the end of time thoughtful spectators unversed
in the mysteries of engineering will pause, as they now do, before
these gigantic towers, more wonderful than the Pyramids, with
the everlasting sea beating their mighty bases, and will perplex
themselves in vain to imagine by what means the granite masonry
could have been laid so solid and true beneath not forty feet
depth of rushing tides alone, but eighty feet below their surface,
on the rock which those tides had not touched for untold ages.
To explain this mystery in one word, the submarine
portion of the tower was really built above-water, in the open
air, and thence sunk toward its bed as soon as built. But this
is to put a new mystery in place of the first, for how could such
a mass of masonry be set firmly to a hair's breadth in its bed
against the mighty current, or how could its bed be excavated
to this enormous depth to receive it?
The principle of the diving-bell, supplemented by the air force-pump,
or compressor, is the solution of the difficulty. Only the diving-bell
must be a peculiar one, made to carry on its back the giant tower
as it dives to the bottom, as it delves into the bowels of the
earth, and as it reposes at length and forever on the rock. It
is technically called a caisson (having been first used
in France), from its resemblance to an inverted chest. Imagine
your diving-bell, or caisson, made of an oblong form, corresponding
to the shape and size of its burden, with a margin of eleven feet
excess on all sides. You must, of course, also have it built with
sufficient durability of material and strength of mass both to
carry down the masonry entire, without flinching, and to rest
under it forever without yielding or decay. It will be best to
have the sides of our oblong diving-bell flare a little, and on
the inner side to taper them to a sort of edge (well shod with
heavy iron), so as to make room for the laborers within to excavate
conveniently to the very extremity of the dimensions of their
diving-bell. To obtain sufficient strength and rigidity in the
structure for its tremendous back-load, let its entire top, 102
feet by 172, be built to a thickness of 22 feet of dense Southern
pitch-pine in timbers twelve inches square, laid in solid courses
crossing each other, fastened with powerful through-bolts, and
all the joints and seams filled with pitch. (The bolts and angle-irons
of this caisson at New York aggregated 250 tons.) Let the sides
be eight feet thick at their junction with the top, built in the
same manner, but tapered on the inside, as already suggested,
down to an iron-shod edge only eight inches thick, and let the
iron bolts and angle-irons, of course, be so strong and numerous
that nothing can loosen timber from timber save by tearing each
stick into splinters. Further, let the back or platform that is
to carry down the great tower in its descent to the bed-rock be
supported at intervals by six cross partitions of solid timber
four feet thick, with a door in each for communication between
the compartments thus formed. These partitions, like the four
sides, will ultimately rest on the bedrock, and bear their part
of the monstrous and everlasting load. Finally, let the whole
cavernous interior be lined with boiler iron, seamed air-tight,
for its perfection as a diving-bell, and for protection against
the danger of fire, which experience in building the first or
Brooklyn tower of this bridge has shown to be imminent at all
times while working by gaslight and with blasting explosives in
compressed air.
Of course there must be means of ingress and
egress for men and materials. There must be a well-hole through
the top, and an iron well leading to it from the open air above-water
for the men to go in and out. It must be lined with iron, continuous
and air-tight with the lining of the interior, and must have an
air-tight iron door, or rather two successive doors with an air-tight
chamber between them large enough for a gang of men to enter,
that the outer door may be closed on them while the inner door
is opened to admit, them to the artificial submarine cavern. This
chamber is called an air lock, and its principle is like that
of a canal lock, or still more exactly that of a pump. In going
out, the men enter the air lock while, its outer door is closed
tight, and after the inner door through which they entered is
closed behind them the outer door may be opened for their egress.
Thus the loss of compressed air by the entrance and exit of a
gang of men is simply what the air lock will contain and no more.
This would be too tedious a process, however, for the removal
of the excavated earth. For this purpose water locks are used.
The iron wells for the removal of material descend through the
caisson into open pits in the ground below the level at which
the water is held down by the compressed air. The water of course
rises in the pits and wells to that level, and thus the compressed
air is "locked" out of them, while the earth and stones
dumped into the pits by the miners in the caisson tumble to the
bottom of the wells, where they can be got at by simply reaching
under water. In each of these wells operates a Morris and Cummings
dredging-machine (either of the grapnel or "clam-shell"
pattern, as each was required), like those constantly seen at
work at one point or another in this and most other harbors where
slips and channels have to be made or deepened, or cleared of
deposits, the difference being that these are of the second class
in size and power, adapted to the capacity of the caisson and
workmen for supplying them with materials. While the harbor machines
of forty horse-power remove 2000 cubic yards of mud per day, the
caisson machines of twenty-five horse-power can raise 1500 yards;
and without working their full capacity, clear the pits of earth
as fast as it is practicable to mine it in the caisson. The iron
"clam-shell" scoop of the machine descends by its chain
to the bottom of the well with its jaws open, plunging into the
mud, where the jaws are drawn together by the action of the machinery
through another chain. This action operates like the pull of a
ship's cable on the anchor, dragging its fluke downward into the
bottom. In like manner the flukes of the dredging scoop are forced
down into the mud as they are drawn together, and grasp a giant
handful, exactly imitating, to use Mr. Roebling's expression,
the action of the human hand in picking up handfuls. The force
of this grasp is illustrated by the fact that large rocks are
picked up as well as earth and small stones, even when only a
corner of the rock is seized between the valves of the scoop.
All the rock blasted out in Hell Gate by the vast submarine excavations
was picked up from the bottom and raised in this way.
While the caisson with its entrances and appurtenances
approaches completion in the shipyard, arrangements must next
be made for placing it in position on the bottom of the stream.
First a slip or dock must be built to fix it in the exact position
of the intended tower. The "water lot" marked for occupation
is levelled as well as possible by dredging, and a row of piles
is driven as deep as possible along the landward line, a length
of 172 feet. At right angles with this a row of piles is driven
out 102 feet into the river from each end, making three sides
of an oblong inclosure or stockade. Into this inclosure the caisson
is towed. The exact lines of the pier foundation are mathematically
fixed by the engineers, and the caisson is placed in the proper
position to a hair by blocking and wedging on all three sides.
It now rises and falls with the tide, however, and is therefore
not yet capable of being exactly and finally placed. The next
business, accordingly, is to commence the foundations of the pier
on the massive platform or raft of solid timber 22 feet thick
and 102 by 172 feet square, which we have figuratively called
the back of the submarine monster which is to carry the whole
burden down to its final bed. The huge squared blocks of granite
are now laid at leisure in hydraulic cement in uniform courses,
and soon their weight overcomes the buoyancy of the caisson, and
settles it to the bottom, with its top still visible above-water.
The compressed air is now let into the diving-bell interior, forcing
the water out beneath the iron-shod edges of the sides where they
rest on the bottom. This done, the workmen can go down into the
very wet cellar, and complete the levelling of the earth under
the supporting edges of the structure. Now, while the caisson
barely touches bottom by its weight, but does not rest too heavily,
the engineers can, with their mathematical instruments and wedges,
finally adjust the mass in exact position, and by easing away
the bottom under it wherever required, with much patience, they
at length get it level, and uniformly supported by blocking placed
under its cross partitions. A few more blocks of granite laid
on will make it immovable. All is now ready for the dredges to
begin lifting out the mud and stones which the men of pick, shovel,
and wheelbarrow pour into the water locks or wells beneath the
dredging shafts.
Many formidable difficulties have thus been surmounted, and
the curious observer now sees how everything so far can be done
by the puny hand of man when guided by his mighty mind. But with
our thoughts fixed on the mountain-like mass of rock descending
full built, we are staggered still by the difficulty of letting
it down eighty feet into the submarine earth, with its position
as plumb and level and unchangeable at every moment of descent
as that of the cornerstone at rest in its bed under any great
building on land. If it should sway from its position ever so
little, the mathematical accuracy and beauty of the whole after-work
would be marred, and what power on earth could move it back a
hair's-breadth toward its place? If a side or a corner should
be hindered or hastened in its descent a little more than the
rest, the mass would be wrenched and disjointed by its own irresistible
weight, and the disintegrating force thus initiated within the
structure could never be eradicated or counteracted. But the mode
of achieving this miracle of descentnot only moving mountains,
but moving them to a hair, through the earth, as the piston descends
in the cylinder of a steam-engineis so commonplace and simple
that it seems almost childish. No machinery of vast and imperceptibly
slow leverage or screw-power, and of admirably scientific adjustment,
is here called to our aid. Nothing but pine blocking under the
six cross partitions of timber on which, as on so many legs or
feet, the monstrous burden-carrier stands. As fast as the earth
is dug away to make room for the descending-tower, the blocking
is knocked away to let it down. Impossible? Let us see. Suppose
a blocking at every two or four feet beneath the supporting partitions,
can not we knock out alternate blockings all round? True; but
how shall we knock out the rest, and what would become of the
structure deprived of support now at this point and now at that,
and pitching downward this way and that with rock-rending force?
Not so fast. By knocking out the alternate blockings we have just
doubled the weight and compression on their fellows. By such increased
compression of its supports the tower has settled in some measure,
of course, and in the most uniform measure possible. Now we just
drive in again the blockings we have removed, as tightly as possible,
after levelling, away the earth under them. But it is evident
that we can not drive them as tight as they were before under
the actual weight of the tower. Besides, the new ground they now
rest on is susceptible of fresh compression. Therefore, if we
next knock out the blockings before undisturbed, the tower will
settle down on the replaced blockings as far as its weight can
compress them and the new ground under them. The fact proves to
be that one complete process of this kind lets the tower down
about one inch by the compression alternately of the two sets
of blockings and the subjacent earth.
But what if our blockings should be driven
tighter or prove harder, themselves or their foundations, at some
points than at others: will not this produce an unequal settling,
and strain the integrity of the masonry? No; for both the weight
and strength of the mass are so predominant as to make nothing
of such minor resistances, and the only result is that the presumptuous
block is crushed. This mode of equalizing the pressure by its
own irresistible weight was frequently observed. Again, if it
be asked how we are to restrain so uncontrollable a mass from
veering in one direction or another from its true position as
it descends, the answer to this difficulty also is given by that
same uncontrollable weight. Since it can not be influenced in
position a hair's breadth by all the power that man could bring
to bear upon it, it will be equally insensible to all the fortuitous
forces that would bias the direction of a more limited mass in
descending, such as bowlders temporarily encountered by the under
edges of the caisson at particular points, or the pressure of
the tides. The mass and its movement are too majestic to suffer
any influence whatever from such casual obstructions. Only if
an obstruction were permanently left in the way at one point,
while the caisson was lowered at other points, could such causes
act against the plumb descent of the structure.
The last operation, after laying bare the bed-rock, and testing
its soundness and solidity at all points, is to fill up the caisson
with a solid hydraulic concrete, which will harden into rock and
unite itself immovably with the rock on which it rests, becoming
to the caisson what a tenon is in a mortise. This concrete is
rammed as tightly as possible under the roof of the caisson; but
if it be impossible to drive it as tight as if the weight of the
tower actually rested on it, this is not amiss. For the continued
and increasing weight on the wooden supports will certainly compress
them further in time, and will eventually, in all probability,
bring the weight of the tower firmly, if not altogether, upon
the incompressible concrete with which the caisson is filled.
With regard to the danger of decay in wood, which presents
itself to most minds in this connection, experience has long since
shown that, when buried beyond reach of air and changes of temperature,
wood is perfectly incorruptible, and will endure, so far as we
can judge, as long as stone. Oxygen, chemically free as it is
in air, is the agent of decomposition, and in its absence all
substances are alike incorruptible. The seaworms make no trouble
at the depth below the bottom where we have left our timber platform.
It may safely be trusted to support the bridge between New York
and Brooklyn as long as there shall be need of it.
The caisson for the Brooklyn tower was towed into its berth
on the 2d of May, 1870. Ten of the fifteen feet thickness of timber
in its roof were built on after this, in situ. On the 15th
of June the first granite blocks were laid on the timber. They
are of from four to seven tons weight. The masonry, faced throughout
with granite, is partly built of the less expensive blue limestone
from Kingston, New York. The compressed air was let in, the water
driven out, and excavation commenced on the 10th of July. The
bed being a tenacious conglomerate of clay, sand, and bowlders,
extending to a great depth, it was not necessary on this side
to sink the pier to the bedrock, and at forty-five and a half
feet beneath the bottom of the river the caisson was filled up
with concrete and left in its final position. The latter operation
was completed on the 11th of March, 1871. Two months had been
lost by the accident of a fire in the caisson, requiring the interior
to be flooded with water to extinguish it. This accident cost
$15,000, and its recurrence in the New York caisson was guarded
against by a lining of boiler iron throughout, at an expense of
$20,000.
The New York foundation was a work of much greater magnitude
and difficulty. From the sandy nature of the ground it became
necessary to sink the pier to the bed-rock, seventy-eight feet
below high-water mark. The process was not different in method,
but was much more trying to the workmen, from the greater pressure
of air required in the caisson to keep out the water. The caisson
was placed in its berth in October, 1871, and rested on the rock
in May, 1872, after less than one year's work in sinking it to
its bed.
The Construction of the towers above the water line was, of
course, a simple though enormous piece of mason-work. The Brooklyn
tower was completed in May, 1875, and the New York tower in July,
1876. Everything was now ready for the work of cable-making, into
which, having already anticipated the construction of the great
floor or bridge proper, we must enter somewhat minutely, to give
the reader a clear idea of its curious and interesting processes.
Let us first imagine the cable as constructedsimply
a bunch of wires, not twisted, but laid parallel, and bound together
by a continuous wrapping of wire. The wires are of size No. 7,
or a little over one-eighth inch in thickness; they number over
5000 in each cable, and make a bundle 15¾ inches thick.
To lay and bind this prodigious bunch of wires straight and parallel
would be impossible except by subdividing the mass into skeins
or strands, which are first laid and bound separately, and afterward
united. Each cable contains nineteen strands of 278 wires each.
They are formed precisely like skeins of yarn or thread. Each
skein is a continuous wire almost exactly one million feet, or
nearly 200 miles, in length, passing from anchorage to anchorage,
back and forth, 278 times. The turns of the wire at each extremity
of the skein pass around a solid block of iron shaped externally
like a horseshoe, with a groove in its periphery, in which the
bend or bight of the skein lies as a skein of yarn is held on
one's thumbs for winding. Each shoe or eye-piece is fixed (after
the strand is finished) between the ends of two anchor bars, a
seven-inch iron bolt passing through the three, and so connecting
the strand with the great anchor chain at either end. After a
skein is fully laid in position (passing, of course, over the
tops of the towers) it is compressed to a cylindrical form at
every point by large clamp tongs, and tightly bound with wire
at intervals of about fifteen inches throughout its length. The
men who do this work go out for the purpose on the strand in a
"buggy," so called, which is a board seat slung by ropes
from the axis of a grooved wheel fitting and travelling on the
strand as bound together. When the strands are thus completed
and duly regulated, the final work of wrapping the cable is accomplished
in a similar manner, as hereafter described.
But to follow the process of construction, we return to the
day when the towers and anchorages stood complete, but disconnected,
with the intermediate spaces occupied only by the trackless air,
and the question was how to initiate a connection between them
all. To this end a three-quarter-inch wire rope, long enough to
reach from anchorage to anchorage over the tops of the towers,
was coiled on board a scow by the Brooklyn shore. First, its end
was hoisted up the water face of the Brooklyn tower, and passed
over the top, let down the land face, and then carried back to
the top of the anchorage, and made fast. Nextwaiting until
an opportunity when the river was clear of vessels at that point,
and stationing boats as to warn coming vessels to haltthe
scow was towed across to the New York tower, paying out the wire
rope into the water as it went. The end remaining on board was
then hoisted up the water face of the New York tower, passed over,
and lowered again on the landward side. Then it was made fast
to a drum connected with a powerful steam-engine, which wound
up the rope from the bed of the river and over the tower, until
it swung clear from side to side in mid-air, and the first connection
between the shores was made. It remained only to carry the New
York end back to the anchorage, hoist it up, and secure it in
position there.
A second span of three-quarter-inch rope was
carried over in substantially the same manner, and the ends of
the two were then joined at the anchorages around grooved driving-wheels
or pulleys, making an endless belt or "traveller" revolving
by steam-power throughout the whole distance from anchorage to
anchorage.
To accomplish the succeeding operations would require men to
work hanging on this slender cord all the way from tower to tower.
Mr. E. F. Farrington, the master-mechanic who superintended this
part of the work on the bridge, and who had previously been engaged
on the suspension bridges at Cincinnati and Niagara Falls, now
took the resolution to make the first passage of the line, and
to give his men as good an example of courage and confidence as
they would ever have occasion to copy.
On Friday afternoon, August 25, 1876, the running gear for
the endless traveller rope was in readiness. A boatswain's chair,
consisting of a bit of board for a seat, slung by the four corners,
with as many short ropes uniting in a ring overhead, was secured
to the traveller rope at the Brooklyn anchorage, and Mr. Farrington
took his seat on the slung bit of board for a private trip over
the line of the future bridge in sight of his men. Having made
his preparations so quietly, and being so quiet a man, his surprise
was great, on looking down from his high starting point, to see
the house-tops beneath him black with spectators, the streets
far below paved, as it were, with upturned faces, the ferryboats
conveying like stacks of humanity, and the New York shore crowded
in a similar manner. As he gave the signal to start the wheels
and swung out, with the rushing rope hissing and undulating like
a flying serpent through the air, the boom of cannon far below
announced to the modest and unsuspecting aeronaut that his intended
private trip for the encouragement of his men was a public triumph.
Away went the whirring rope, invisible or like a spider's thread
to the eyes below, bending and swaying with the human weight that
rode its cantering waves, to all appearance self-impelled, like
some strange creature of serpentine flight, sweeping first downward
toward the house-tops till the deepest curve his weight could
give the slender rope was passed, and thence soaring sharply upward
to the top of the first tower in his course. Here he gave a signal
to slow the rope nearly to a stop, while the men on the tower,
with excited cheering, lifted the rope and its slung rider over
the parapet, supported both across to the other side, and launched
them off the dizzy height again. Again the cannon roared, and
the myriads of spectators swung their hats and cheered with wild
excitement, while all the steam-whistles on land and water shrieked
their uttermost discordance. The trip occupied twenty-two minutes,
and at the end the explorer was glad to hide from the pursuing
crowds that would fain have caught him as a trophy and carried
him through the streets in triumph.
It was after this an easy matter to carry
across the other carrier ropes; the ropes from which the "cradles,"
or hanging platforms, for regulating the wires, were suspended;
those which supported the foot-bridge for the workmen, over which
sight-seers were sometimes allowed to pass; and the "storm
cables," which, stretching upward from the towers below the
roadway, steadied the temporary structure against the wind.
Meanwhile all was ready in the large sheds that covered the
Brooklyn anchorage for the regular and long-to-be-protracted machine-work
of cable-making. Thirty-two drums, eight feet in diameter, were
rigged in the position of carriage-wheels just clear of the floor,
eight drums behind the destined position of each of the four cables.
Hundreds of coils of wire, already delivered in the yard below,
had been dipped in linseed-oil and dried again and again. A screw
thread had been cut on every end of wire by a convenient machine
constantly at work for this purpose (opposite ends being cut with
right and left screws respectively), and the little steel coupling
tubes, with inside screw-threads to match, had united fifty-two
coils, or nearly ten continuous miles of wire, upon each of the
thirty-two drums.
Now the shoe, or eye-piece, around which the skein of wire
to form a strand of the cable is to be turned at each extremity,
is secured in a temporary position on the anchorage, and the work
of winding the skein is begun. A wire is fastened to the shoe,
and passed around a sheave or grooved pulley fixed and suspended
to the traveller rope by iron arms reaching up from its axle.
The traveller rope is set in motion, and bears forth the sheave,
carrying the bight or turn of wire before it, thus taking across
two spans, or a complete circuit, of the wire at once. On reaching
the New York side (which takes about eight minutes) the bight
of wire is passed around the shoe, completing once the circuit
of the skein. The sheave, released, returns empty to the Brooklyn
side.
Next the circuit of wire that has been carried
across must be "regulated," that is, adjusted to the
exact length and height required by its place in the strand. On
the top of the Brooklyn tower, first, a clamp is fastened on the
first span of wirei.e., that directly reaching from
the end fastened at the Brooklyn anchoragea small tackle-block
is hooked on, and two men haul up the slack between the tower
and anchorage until the regulator men in the cradle signal that
the position is accurately adjusted at their respective points.
A similar regulation is made on the New York tower to adjust the
curve of the wire between the towers, and the same process is
likewise repeated on the New York anchorage, until the fall of
the wire off that point is also accurately located. The return
span is then adjusted in the same manner, in reverse order, beginning
at the New York tower. On the Brooklyn side, when the last span
of this circuit of wire is adjusted in position, it is passed
around the shoe, held fast, and the bight is again placed on a
sheave, and the traveller starts again to carry over a second
circuit of the skein. Thus the skein is wound round and round
its eyepieces at either anchorage with unbroken continuity, with
uniform tension, and with exact parallelism between all its threads,
until the full number of 139 circuits has been made, and 278 wires
are ready to be bound together in a round and solid cord three
inches thick. On either side the eyepiece, of course, the cord
is parted, and for a few inches is bound in two separate strands
of 139 wires each, but it is shortly brought into one, leaving
a loop at each end of the strand, inclosing the eye-piece or shoe,
which, as before stated, is pinned between and together with two
of the eighteen anchor bars in which the great anchor chains unite
with each cable. Strands for each of the four great cables are
made and placed simultaneously. A circuit of wire is laid and
regulated in about thirty minutes, including ordinary delays.
Two travellers are running, so that four circuits, or eight full
lengths, of wire might be laid per hour. If weather never interfered,
the 21,000 wires of which the four cables are composed could have
been laid in less than a year. In point of fact, however, as it
was useless to make the strands faster than the engineers could
locate and adjust them in the cableswhich is the grand difficulty
of the workit was doing well to lay forty wires on an average
each working day.
On the commencement of impracticable weather in winter, such
as incrusts the wires with snow and ice, it becomes impossible
to regulate the wires properly. Then the work is necessarily suspended
for the time being.
But the chief delay, as before remarked, arose from the difficulty
of regulating the strands from two causessun and wind. Obviously
the unity and strength of the cable depend on getting each strand
into its exact and peculiar place. As the locations of the individual
strands vary in height, the strands must vary in length. Each
must hang in its own peculiar length and curve to a mathematical
nicety; for if left but half an inch too long or too short for
its true position, it will be too slack or too taut for its fellows,
and it will be impossible to bind them solidly in one mass, and
make them pull equally together. In the abstract this is a matter
of exact mathematical science. But in practical engineering the
actualization of the calculations is interfered with by variable
forces which can not be resisted, evaded, or calculated. The chief
of these in cable-making is temperature, which fluctuates so irregularly
and unceasingly that the length of the strand is rarely the same
for an hour together; and what is far more baffling to the engineer,
the different spans are unequally acted on by the sun. One curve
is in shadow while another is in full sunshine; one is exposed
vertically to the sun, while another is struck by its rays at
an extremely dull angle. In short, when the sun shines the several
curves of each strand are all "at sixes and sevens,"
too unstable in position to be adjusted. The same is true of them
in another sense when they are kept swaying and undulating by
the wind. Hence the engineers can do nothing with them except
at hours when two conditions concurfreedom from the influences
of wind and direct sunshine. The hours from daylight to sunrise
(when calm), and occasionally a few hours of calm and cloudy weather,
are the only times available to the engineer for adjusting the
length of his strands. This is done by changing the position of
the "shoe." The figures of the engineer show that the
deflection of the cables from the tops of the towers is 127.64
feet at 50 degrees F., while at 90 degrees it is 128.64 feeta
variation of nearly one-third of an inch for every degree of temperature,
so that the engineer is likely to find his cables varying as much
as half a foot in height In the course of a day. In short, the
ponderous thing, though neither small nor agile, has a trick in
common with the minute and lively insect which, when you put your
finger on him, isn't there.
The running and regulating of the cable wires
commenced June 11, 1877, and the last wire was run over October
15, 1878. The nineteen strands for each of the four cables having
been thus made and located, the final operation is to unite and
wrap them with wire. This is done by a little machine. An iron
clamp is provided, the interior of which is of the size and cylindrical
shape of the cable before wrapping. The temporary fastenings of
wire around each strand are removed as fast as this work proceeds,
and the clamp, screwed tightly, compresses the nineteen strands
together, symmetrically arranged in a true cylinder, with the
odd strand in the centre, and the other eighteen filling two circles
around it. The wrapping machine follows up the clamp, and binds
the cable with a close spiral wrapping of wire. This machine or
implement consists of an iron cylinder cast in halves, to be bolted
together about the cable, compressing it firmly. A reel or drum
of wire encircles the cylinder. The wire winds off the drum through
a hole in a steel disk on the rear end of the cylinder, whence
it passes with a single turn around a small roller attached to
the disk, and thence to the cable. The disk is turned by hand
by a lever attached to it, and thus the wire, being held in severe
tension by its turn around the roller, is tightly wound on the
cable, and as it advances in its spiral or screw travel pushes
forward the cylinder from which it is reeled.
The cables, thus completed, were ready for their load, the
floor or bridge proper, already described. The suspender bands
were next put on the cables; to these are attached the wire rope
suspenders, and these in turn hold the steel floor beams of the
roadway. The suspender bands are made of wrought iron five inches
wide and five-eighths of an inch thick. The bands are cut at one
point, and the two ends turned outward, so that they may be opened
(by heating), and placed over the cables. The two ends, or ears,
which hang vertically down when the bands are in place, have holes
through them for a screw-bolt one and three-quarter inches in
diameter, which serves as the support of the suspenders, and also
for tightening the bands and the cable. By the aid of these suspenders
at short intervals all the way, it was easy to place, first, the
crossbeams of the bridge floor, beginning with those nearest each
anchorage and each face of the towers. The nearest suspenders
hanging ready to receive the first iron beam had only to be drawn
in and attached thereto by their clamps or stirrups, and the beam
was swung out in position, ready to support planks for the workmen
to stand on and launch the second beam, and so on. The cross beams
being laid and braced together, forming the horizontal truss,
the vertical truss-work is also put in, with the diagonal bracing
below the floor, and the stays from the towers both above and
below, and the bridge is at last ready for the planking.
The suspenders are for the most part at equal distances from
each other But it will be noticed that at the centre two suspenders
from each of the four cables hang close together, sometimes but
a few inches, sometimes more than a foot, apart, These give the
clew to that problem of engineering and puzzle to the public as
to how the expansion and contraction, by heat and cold, of the
floor or bridge proper, are to be provided for. The great span
may be said to be in two pieces or half-lengths connected at the
centre by an "expansion joint." Each half of a truss
is attached to one of the two suspenders mentioned, and the two
halves are connected by plates attached to one, and sliding in
channels or ways in the other. No weight comes upon these guide-plates,
as the two suspenders support the halves of the truss independently
of each other. The planking is so arranged as to be always continuous,
and the iron rails for the cars are at this point split in half
lengthwise, so that one half plays upon the other, guide-rails
on either side protecting the cars.
At 118 feet above high-water mark each of the towers of the
bridge is divided into three masses by the two broad openings,
31½ feet wide, which here commence. The six lines of the
great steel trusses or framework forming the bridge pass, unbroken
in their continuity, through these openings of the piers, resting
on the masonry underneath, and firmly anchored down to it by huge
bolts and ties of wire rope. An idea of the strength of these
trusses may be obtained when it is considered that for over one
hundred feet out from each side of the tower they are of themselves,
without any support whatever from the cables or stays, sufficiently
strong to carry all the load that may ever come upon them. The
openings continue to the height of 120½ feet, where they
are closed by pointed arches. Above these arches the reunited
tower rises thirty feet higher, where it receives a set of iron
bed-plates, on which rest the "saddles" in which the
great suspension cables ride. These are iron castings in the form
of a segment of a circle, with a groove to receive the cable on
the upper and convex side. The under and plane side lies on a
layer of small iron rollers held in place by flanges on the surface
of the bed-plate. The object of these is to give sufficient play
to the bearings on which the cables rest to prevent the cables
themselves slipping and chafing in the saddles if affected by
the force of storms or variations of load, or when lengthening
and contracting under changes of temperature. From the saddles
each way the cables sweep downward in a graceful curve, the landward
ends entering the anchor walls, as already described, and supporting
the shore ends of the bridge, while the main bow, or inverted
arch, hanging between the towers, holds up the central truss of
nearly 1600 feet span.
A great work of engineering is a battle with nature, in which,
as in other wars, Death must take his toll. There have been employed
upon the works at one time as many as six hundred men, a small
army in themselves, and in the fourteen years since the master-mind,
John A. Roebling himself, became the first sacrifice, more than
twenty men have been fatally hurt. Several more have been victims
to the it "caisson disease,"* resulting from
working in compressed air; but, despite the dizzy height, no one
has fallen from the main span into the water below. Besides the
fire in the Brooklyn caisson, which cost no lives, and the fall
of the derricks on the Brooklyn tower, which had more serious
results, there has been one great accident only; but the imagination
can scarcely picture anything more dreadful. On June 19, 1878,
one of the great strands broke loose from the New York anchorage,
carrying with it the "shoe" and its ponderous attachments.
As the end swept from the anchorage it dashed off several of the
men at work, and then, with a frightful leap, grazing the houses
and peopled streets below, it landed for the instant in the bridge
yard close under the Now York tower. The great weight mid-stream
whizzed it over the tower with frightful and increasing rapidity,
and the whole span plunged madly into the river, narrowly missing
the ferry-boats that ply, crowded with human freight, below the
line of the bridge. In these years the enterprise has lost also
its president, Henry C. Murphy, and its first treasurer, J. H.
Prentice, as well as its chief engineer. But, in strange and happy
contrast, there has not been a single break in the engineering
staff, Engineers Martin, Paine, Collingwood, McNulty, Probasco,
and Hildenbrand having served continuously, most of them from
the very first. And now all the extraordinary engineering difficulties
are overcome, and with them the vexatious delays from unfriendly
opposition, political feuds, the stoppage of financial supplies,
and the adoption of a new structural material. In a few years
these will have been forgotten, and the forty million passengers
who are expected to cross the bridge yearly will think only of
the great boon that emancipates them from the delays of fog and
ice, the possible collisions, and the old-time delays in waiting
for the ferry-boats. Yet the ferries will still have plenty to
do.
The summer of 1883 will be memorable for the opening of the
great bridge, uniting New York and Brooklyn into a metropolis
of nearly two million peoplea population that will soon
outgrow Paris, and have only London left to vie with. The bridge
is practically a new street, belonging jointly to the two cities,
and making with Third Avenue, the Bowery, and Chatham Street,
New York, and Fulton Street continuing into Fulton Avenue on the
Brooklyn side, a great thoroughfare fourteen miles long, already
continuously built up, from the Harlem River to East New York.
This is longer than the great street which stretches east to west
across London, under its various names, from Bow to Uxbridge Road,
spanning the valley where was once the Fleet brook by that other
fine work of engineering, the Holborn Viaduct. The bridge roadway
from its New York terminus opposite the City Hall to Sands Street,
Brooklyn, is a little over a mile long (5989 feet), and it will
take the pace of a smart walker to make the aerial journey, with
its arched ascent, in twenty minutes. The cities will probably
decide, confining the tolls to vehicular traffic, not to charge
him the one cent first proposed for the privilege of taking this
trip on "foot's horse." But for five cents he can jump
at either end into fine cars, built on the pattern of the newest
Manhattan elevated cars, which move apparently of their own volition,
until one finds the secret in the endless wire rope underneath
that is worked by stationary engines on the shore and makes continual
circuit, across under one roadway and back under the other. These
will take him across in a little less than five minutes, and it
is not improbable that through trains will ultimately convey passengers
from the northernmost end of New York over the Brooklyn Elevated
that is to be, bringing them nearer to the health-giving beaches
of Long Island by nearly half an hour's time.
But the wise man will not cross the bridge in five minutes, nor
in twenty. He will linger to get the good of the splendid sweep
of view about him, which his aesthetic self will admit pays wonderful
interest on his investment of nothing. The bridge itself will
be a remarkable sight, as he looks from his central path of vantage
down upon the broad outer roadways, each with its tide of weighted
wagons and carriages of his wealthier but not wiser brethren,
and nearer the centre the two iron paths upon which the trains
move silently and swiftly. Under him is the busy river, the two
great cities now made one, and beyond, completing the circuit,
villa-dotted Staten Island; the marshes, rivers, and cities of
New, Jersey stretching to Orange Mountain and the further heights;
the Palisades walling the mighty Hudson; the fair Westchester
country; the thoroughfare of the Sound opening out from Hell Gate;
Long Island, "fish-shaped Paumanok," with its beaches;
the Narrows, with their frowning forts; the Bay, where the colossal
Liberty will rise; at last the ocean, with its bridging ships.
And when he takes his walks about New York he can scarcely lose
sight of what is now the great landmark which characterizes and
dominates the city as St. Peter's from across the Campagna dominates
Rome, and the Are de Triomphe the approach to Paris, and the Capitol
on its height our own Washingtonthe double-towered bridge,
whose massive masonry finds no parallel since the Pyramids. Those
huger masses were the work of brutal force, piling stone upon
stone. The wonder and the triumph of this work of our own day
is in the weaving of the aerial span that carries such burden
of usefulness, by human thought and skill, from the delicate threads
of wire that a child could almost sever.
* The "caisson disease" is the result
of living under atmospheric pressure greatly above that to which
the human system is normally adapted. The blood is driven in from
the exterior and soft parts of the body to the central organs,
especially the brain and spinal cord. On emerging into the open
air, violent neuralgic pains and sometimes paralysis follow. Advanced
consumption is, on the other band, stayed, and sometimes remedied,
by compressed air. Dr. Andrew H. Smith, surgeon to the Bridge
Company, reported one hundred and ten cases of the "caisson
disease," of which three were presently, and probably more
finally, fatal.
Brooklyn Bridge | Bridge
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