XXVIII.
THE EAST RIVER BRIDGE.
LAYING THE FOUNDATIONS UNDER WATER.—HOW THE WORK WAS PERFORMED.—THE CAISSON.—HOW IT IS MADE.—ITS MODE OF OPERATION.—WORKING UNDER WATER.—EXPLORING THE BED OF THE RIVER.—DESCENDING INTO THE BOX.—EFFECTS OF A GREAT PRESSURE OF AIR.—AN UNPLEASANT SENSATION.—A STRANGE SIGHT.—ACCIDENTS.—HOW A MAN’S ARM WAS CAUGHT.
A bridge to connect New York and Brooklyn has long been desired, and many plans for such a structure have been made. It was finally determined to erect a suspension bridge high enough to permit the passage of ships beneath it, and stretching, in a single span, from one side to the other of the East River. Work was begun in 1870, and continued, with occasional interruptions. The bridge, by comparison with similar structures, is the longest and largest of its kind in the world.
The Brooklyn Suspension Bridge—Now Building.Length of River Span, 1616 feet.Length of New York Approach, 1441 feet.Total Length, 5878 feet.Each Land Span, 940 feet.Brooklyn Approach, 941 feet.Total Height above High Tide, 268 feet.
The Brooklyn Suspension Bridge—Now Building.Length of River Span, 1616 feet.Length of New York Approach, 1441 feet.Total Length, 5878 feet.Each Land Span, 940 feet.Brooklyn Approach, 941 feet.Total Height above High Tide, 268 feet.
The bridge rests on two piers, one on the east and the other on the west bank of the river. The eastern pier was begun some time before the other, and the work of laying its foundations was of a peculiar character. Ordinarily, where a pier is to be set in the water, a coffer dam is built around the place where it is to stand, and the water is pumped out. But in the present instance, this mode of working was deemed impracticable, and it was decided to lay the foundations by means of a caisson. This is quite a curiosity in its way, and well deserves a visit and a description. I did not visit the one on the east side, but deferred my caisson explorations till the work on the west side was under way.
On the invitation of Colonel Paine and Engineer Cottingwood, I was one of a party of four to descend into thecaisson to examine its workings and inspect its machinery. Arriving at the foot of Roosevelt Street, we found indications of the construction of a large building. There were numerous derricks, scaffoldings, and building materials in the vicinity, and every where there was activity. Just as we reached the works we found a gang of sixty men indulging in hot coffee, which is always served to them previous to their descending the shaft of the caisson. Their coffee drinking over, and the roll-call answered, they walked in single file to the mouth of the shaft, and there waited the arrival of those whom they were about relieving.
Most of the men wore nothing but their shirts and trousers, with water-proof boots reaching above the knees. At a signal given by the foreman of the gang, some of them entered an elevator, while others proceeded down a spiral staircase, and were soon lost to view. Before taking the reader to the interior of the caisson, it may be well to state that it is nothing else than a large box of iron and wood, the full size of the intended abutment. This box is turned bottom upward, and rests upon its edges.
DESCRIPTION OF THE CAISSON.
It is one hundred and two feet wide, and one hundred and seventy-two feet long, and nearly ten feet in height. Its immense weight is supported by several solid trusses of oak and iron, which run across the caisson; and in addition to this, it receives an upward support of forced air equal to forty thousand tons. The pressure of the air in the caisson is forty-four pounds to the square inch, being twenty-nine pounds more than the ordinary atmospheric pressure.
The air is sent down the caisson by means of pumps, there being fourteen engines, each of twenty-four horse power, constantly at work. In the centre of the caisson, an entrance is obtained by means of a shaft having a spiral staircase of over one hundred circular steps, and there is another entrance by an elevator, which, by the by, is the most agreeable way of descending, particularly if the visitor is inclined to corpulence.
It was down this entrance I went with the rest of our party.Like the workmen, each of us swallowed a small quantity of hot coffee and biscuit, as we were told that we should suffer less from the effects of the descent. Under the direction of our guide, we took our stand inside the elevator, for the simple reason that we could not sit. There were no velvet-covered seats, as are generally found in hotel elevators.
GOING INTO THE INTERIOR.
At a given signal, we began our journey into the East River, and descended until we reached what our conductor termed the “lock.” Here we changed our stands again, and entered the lock by crawling through an opening at the bottom of the elevator sufficiently large for a man of ordinary size to pass easily. This lock is an oblong iron box, or boiler, of just sufficient size to allow half a dozen persons to stand erect. It is eight feet long, and six feet in diameter. At the bottom of the lock there is an iron door or opening, similar to that through which we entered, which gives admission to the interior of the caisson. These iron doors are fitted with rubber, so as to make them perfectly air-tight.
When we had all entered, the door was closed upon us. We looked at each other, wondering what would be done next, and we soon found out. Our conductor, previous to starting the lock, gave us what he termed a few useful hints, so that we might be able to make the trip as agreeable as possible under all the circumstances.
“Now, gentlemen,” said he, “in descending, you will find a disagreeable sensation, particularly about your ears. You will find great ease by closing the nostrils every few seconds,—as the pressure of the air will act upon the tympanum of the ear,—and also by inflating your cheeks to their full extent.”
These instructions were given that we might cause an artificial pressure upon the inside of the ear, and thus prevent its rupture.
Our conductor then proceeded to turn a cock, to admit the air forced from above. In a moment it rushed in with a tremendous force, making a noise similar to that of a locomotiveblowing off steam. The effect of this was anything but pleasant. A sudden deafness seemed to overtake us, as if a cannon had been fired under our noses; our voices were also changed, and appeared cracked, and we almost wished our curiosity had not led us so far.
A HEAVY PRESSURE OF AIR.
This feeling was caused by the air rushing too fast into the orifice of the ear. There was just sufficient light inside the lock to discern our faces, and that was all. It took five or six minutes to get the necessary amount of pressure into the lock, and then the air was turned off.
We seemed suddenly to lose our footing, and then to regain it; and no sooner had we righted ourselves than we had another sudden shoot, and this continued until we reached the bottom. The actual descent was made in about a minute and a half, or perhaps two minutes; but owing to the pain we suffered, it appeared to be three times as long.
The sensation we experienced was certainly very disagreeable and painful, and for a pleasure trip I certainly would not recommend any one to undertake the journey. Should a lady go down, however strong-minded she might be, I would not answer for the consequences. One of the party was so much affected by the pressure of the air that our conductor had to turn off the cock frequently. The stranger’s ears pained him greatly, and blood began to spurt from them.
Having reached the bottom of the caisson, where the workmen were digging out the earth and blasting rock, we were detained in the lock some minutes, to allow the admission of air of the same density as that below. This being done, I descended a short iron ladder leading into the bottom of the caisson, and speedily found myself standing on the bed of the river, seventy-eight feet below water-mark.
There were several men working in their shirt sleeves, with big drops of perspiration rolling off their cheeks. The subterranean vault was very well lighted with gas forced down the pipes in the same manner as the air; and it is a curious fact, that in the compressed air a foot burner gives as much light as a four foot one would in the ordinary atmosphere.The caisson seemed to be full of steam, as if a hundred washerwomen were plying their avocation at the tub. The bottom of the caisson is divided into several chambers by means of iron and wood partitions, with entrances leading into each other. The air does not seem impure nor unpleasant. According to an examination made a few days before my visit, it was then found to contain a small percentage of carbonic acid, but not enough to do any harm.
OPERATIONS BELOW.
As soon as the sand is dug, it is sent up various pipes, four inches in diameter, which operate in the same way as siphons. It is odd to notice with what force the sand ascends to the top of the caisson, and it is all that six men can do to shovel it in fast enough. Boulders of trap rock were found embedded in the quicksand. These were broken up and hoisted out by an apparatus similar to a dredging machine, working in an immense shaft filled with water.
The shape of the interior of the caisson resembles very much the lips of an enormous bell, and in reality it is worked upon the same principle as an ordinary diving-bell, the water being kept out by the great pressure of air. As soon as the caisson is perfectly settled, and all the sand and debris down to the bed rock is removed, the interior is filled with concrete and masonry, and thus the pier obtains a foundation perfectly solid.
While making a tour through the various chambers, I found a pair of doves, which had been placed there for testing the effect of the compressed air. The birds appeared to have become accustomed to their new habitation, where they had been for several weeks. They looked, however, rather disconsolate and sickly, and I learned, a day or two later, that one had died from the effects of its imprisonment.
A black and tan terrier had also been taken into the caisson, but after it had been down a few hours it became paralyzed in its hind legs, and was taken up; and for more than a fortnight it did not recover from the shock to its system.
SCENES IN THE CAISSON.
The scene in the caisson is a very novel one. The water, seen through the gas jets, sparkles in the pools at the bottom of the river, the men are toiling and perspiring amid the rushing and rumbling noise of the sand siphons, and everything appears in confusion. While our party was making its tour, it was found that our voices had completely changed; each one appeared to stutter, and altogether the voice had a very unnatural sound, as if we spoke in a half screeching key.
An attempt was made to whistle, but whistle we could not. The lips might be puckered, and you might blow as hard as you pleased, but it was all in vain, as not a note could be heard. Some of us tried to whistle by our fingers, but were unsuccessful.
Communication is had with the upper-world by means of a movable iron rod and a couple of dials, one above and the other below. These form the telegraph. On each dial are printed, in plain letters, the words, “All right,” “Start,” “Faster,” “Slower,” “Stop,” “Less,” “More,” “Bucket is caught,” “Highest corner,” “Stopped,” “Come up all;” and the last is the most pleasing call of the entire number to the laborers below.
Adjoining the dial is a thermometer, which indicated the atmosphere to be eighty-two degrees Fahrenheit.
Accidents occur in the caisson, in spite of all precautions. A short time before my visit, a small stone caught in the pipe of the siphon, and one of the workmen came very near losing his arm while attempting to pull it out. His hand was drawn into the pipe, as if by a powerful magnet. The man was thrown upon his face by the great power of the atmosphere, and at the same time his arm was drawn up the pipe: had it not been for four of his comrades instantly pulling his arm down, the limb would have been torn from his shoulder. He received severe injuries, and is not likely to be so careless again. The skin of the arm looked as if a quantity of boiling oil had been poured over it, and it soon became blistered from his shoulder downward.
After a stay of nearly an hour, the party proceeded to return once more to terra firma. We entered the lock, as on making the descent, through the small iron door; then the compressed air was allowed to escape until the pressure of the air was equal to that of the atmosphere outside.
CHANGE OF ATMOSPHERE.—THE JAMS.
While this was going on, a peculiar sensation was experienced, but it was not as disagreeable as that of making the descent. It seemed as though there was a rush of water through the ears, and we were diving. Ascending to the top of the caisson occupied about ten minutes, as the physician in attendance recommends that the change from the high pressure should not be made rapidly. We were all glad to breathe the pure air and enjoy daylight again. Several of the workmen stated that nearly every day some of them suffered from the work below, and said one,—
“We have all had the jams.”
“What are the jams?” said I.
“Well,” said another, “they ain’t the jim-jams, brought on by drink, for we dare not take much, but a feeling like the flesh a tearin’ off of our bones.”
“We have the cramps in our legs, body, arms, and chest,” said another, “and at times it causes us so great pain that we cannot work; we do not notice anything amiss until we have been out of the caisson for some hours, sometimes not until the next day. These ‘jams,’ as we call them, go away as quickly as they come, but sometimes return after another visit to the caisson.”
The men are cautioned to abstain from drinking spirits, but with some the caution is not heeded, and those that will drink spirits in preference to coffee are generally the greatest sufferers.
The construction of the abutments of this bridge is a novel one. It was first introduced on the building of the St. Louis suspension bridge, and since then great improvements have taken place. When completed, the bridge will be a noble monument of engineering skill.