The Great Bridge

by David McCullough

  Outside, on the top of the caisson, such a disparity, in the level of the water in the shafts could be an alarming sight for anyone on duty who did not understand the reason for it. The impression would be that the lower of the two shafts was getting close to the danger level-that it might may blow out at any instant-and the immediate response would be to feed more water into the shaft as quickly as possible.

  This is precisely what happened on more than one occasion and effect inside, naturally, was that the pool beneath one shaft would begin overflowing rapidly, which led those in charge below to assume the air pressure in the chamber was giving out. And since there was no direct communication between those above and those below, somebody had to scramble up through the air lock and find out what had gone wrong. On one such occasion it was discovered that the water in one shaft was above twelve feet from the top while the water in the other shaft was twenty-one feet from the top and despite the fact that a heavy stream of the water was pouring into the shallower shaft. The water was immediately shut off when it was known what was happening below and samples of water were taken from each shaft. Water from lower shaft was found to weight eighty-five pounds per cubic foot, which was twenty-one pounds more than the water from the other shaft.

  On the Sunday of the blowout, apparently the sediment in one shaft had settled to such an extent that the water no longer weighed enough to contain the pressure inside. The normal precaution had been to keep a small stream of the water playing into the shaft to make up for just a likelihood during the days when the work was halted and no dredging was going on. But this time had not been done. Sounding very much like his father, Roebling said “To say that his occurrence was an accident would certainly be wrong, because not one accident in a hundred deserves the name. In this case it was simply the legitimate result of carelessness, brought about by an overconfidence in supposing matters would take care of themselves”

  Trusting matters to take care of themselves was something this extremely competent young man had seldom done in his life. He had had the contrary attitude drummed into him since childhood and from here on more than ever, he would insist on the strictest attention to every detail and to safety precautions especially, and he would come down hard on anyone caught taking such matters lightly. The thing to fight against, he told the men, was the kind of carelessness that comes from familiarity with the job.

  10

  Fire

  When the perfected East River bridge shall permanently and uninterruptedly connect the two cities, the daily thousands who cross it will consider it a sort of natural and inevitable phenomenon, such as the rising and setting of the sun, and they will unconsciously overlook the preliminary difficulties surmounted before the structure spanned the stream, and will perhaps undervalue the indomitable courage, the absolute faith, the consummate genius which assured the engineer’s triumph.

  —THOMAS KINSELLA, in

  The Brooklyn Eagle

  A SECOND contract was signed that October with Webb & Bell to build the New York caisson, according to plans drawn up during the summer. This time the caisson would be slightly larger and there were to be a number of important modifications. Roebling had decided to make the water shafts round instead of square, for example; he wanted the air locks positioned differently; and the entire interior would be lined with boiler plate, as fire protection, Roebling having realized by this time how very inadequate were the preventive measures he had specified in the Brooklyn caisson. With a caisson that might have to go twice the depth of the Brooklyn caisson, he wanted none of the anxieties there had been over fire.

  In November actual construction of the New York caisson got under way at Webb & Bell yards on the other side of the river, while the Brooklyn caisson continued steadily downward. Things were proceeding very nicely now. In the middle of the month Harper’s Weekly published a spectacular double-page view of lower New York and Brooklyn, as though seen from the air (“an unprecedented piece of engraving”), and there, bestriding the East River, bigger and grander by far than anything in sight, was the finished bridge. “This bold and peculiarly American design is not yet wholly beyond the scope of debate,” wrote the editors, whose offices on Pearl Street looked out on the spot where the New York tower would stand. But the beautiful engraved view, placed in the magazine so it could be easily removed and saved by the reader, suggested quite clearly, if their words did not, that they had every confidence in successful results. And for the technical community, Scientific American announced about the same time that “the rapidity with which the work has proceeded is evidence that it is conducted by a man who is fully competent to conduct this greatest engineering feat of modern times,” implying, it would seem, that there had been some doubts about that.

  By the end of the month the Brooklyn caisson had reached a depth of almost forty-three feet, or very nearly as far as it would have to go. Another two feet, maybe even less, another ten days would do it, Roebling told the others. In the drafting room, plans were being drawn up for brick piers, ten feet square, that he had decided to build throughout the interior of the caisson, once it was at rest, to provide absolutely solid support for the mounting load overhead during the time it would take to fill the vast chambers with concrete. An order had already been placed for a quarter of a million bricks.

  So the end of this first momentous step seemed very near indeed, when, on the morning of Friday, December 2, about the time most people were on their way to work, the news swept through Brooklyn that the caisson was on fire.

  The fire had been discovered about nine thirty the previous evening. It had started several hours before that, as near as anyone could judge, in a seam where the frame between chambers No. 1 and No. 2 joined the roof. Every other seam in the roof had long since been pointed with cement, but this one for some unknown reason had been overlooked and the highly inflammable oakum caulking put in when the caisson was being built had been left exposed. In chamber No. 2, just below the place where the fire was discovered, a workman named McDonald had nailed a wooden box about head high, where he evidently stored his dinner pail, and during the change of shifts at three, in order to see into the box, he must have held his candle against the seam just long enough to start the oakum burning.

  There had been four or five fires in the caisson before this one, in the summer when the men were still unfamiliar with working in compressed air. But none of those early fires had amounted to very much. They had been put out quickly by the men themselves, without any help from the fire department, or any public knowledge that they had ever happened. The pressure then was still comparatively mild and there was still plenty of river water in the chambers to drown fires with. But the need for extreme caution in such an oxygen-charged atmosphere had been pretty clearly demonstrated, and particularly if one imagined the same thing happening when the caisson got down to a depth where the river would be sealed out. Roebling wanted no chances taken. In the time since, he had had steam pipes introduced, as well as fire extinguishers and a couple of hoses that could throw an inch-and-a-half stream at sixty-five pounds of pressure. Two men had also been assigned to do nothing but watch over all the lights.

  Because the fire began directly above the frame, it had remained undetected until the frame itself had burned through near the roof. But once it was discovered, there was a sudden, loud panic among the eighty men inside the caisson at the time. Tools were thrown down, wheelbarrows were overturned in a rush for the ladders. But that had ended quickly enough. Charles Young, the foreman, got the men under control. Nobody left the caisson and Young ordered some of the men to start packing wet clothes, rags, and mud into the cavity where the fire was burning to shut off the draft of compressed air as much as possible.

  The charred opening of the cavity was only about as big as a fist, but inside it looked to be about seven feet long and maybe a foot or more wide and it was all a mass of flame. Men tried throwing buckets of water up into it. Then steam was turned into it for fifteen or twenty minutes. T
he fire extinguishers were tried after that: two big cylinders of carbon dioxide under several hundred pounds of pressure were discharged into the fire in an effort to smother it. But none of this had any noticeable effect. The instant the steam or the fire extinguishers were turned off the timbers would ignite again.

  About ten o’clock, or half an hour after the fire was discovered, Roebling was sent for, and by the time he had come down through the air lock, the hoses had been put into service and were enough to extinguish all the fire, or at least all anyone was able to see. Still, as Roebling noticed immediately, a violent draft of compressed air was rushing through the aperture. He had most of it stopped with cement, but kept the water steadily playing into it for the next two hours, the force of the water being greatly enhanced by the draft.

  In the meantime, Farrington, the master mechanic, had also been sent for and Roebling put him to work drilling holes into the roof to see how far the fire had penetrated. Several holes bored up to two feet showed no signs of fire. Others were then bored a foot deeper and they too showed nothing. But this work went terribly slowly and the tension for everyone was agonizing. Time was lost lengthening out augers, as Roebling told the story later, and the draft carried the chips up into each hole as it was being drilled. There was also the anxiety of knowing that every new hole meant the introduction of another draft of compressed air into the yellow pine and even a small draft of such air, they all realized, would have about the same effect on smoldering wood as a huge bellows.

  It was a strange, unnatural kind of fire they were fighting. There was no flame to be seen now and in the dense atmosphere of the caisson, charged already with lamp smoke and blasting powder, it was impossible to see or to smell whether the cavity was smoking. There was no telling either what damage was being done out of sight, or to what depths the compressed air might force the fire into the fifteen layers of timber overhead, in just the way a great weight might force a spike into wood.

  Roebling worked feverishly with a few hand-picked men; the rest he had get back to their regular duties. He did not intend to lose a night’s work unless he absolutely had to. His own efforts for the next several hours would be described as “almost superhuman” by those who were there.

  The question of flooding the caisson came up. To put the fire out some less drastic, simpler way would be immensely preferable, Roebling said, but if they were to find that the fire was not out, as it appeared to be, then, he said, it was only a matter of time until the entire foundation would be destroyed. The fire would eat through the immense pine roof like a hidden cancer, destroying one course of timber after another, until the structure was so weakened that the vast weight overhead (now about 28,000 tons, Roebling calculated) would come crashing through.

  The problem with flooding, however, was comparable to that of a blowout. Even if water could be substituted for the compressed air as rapidly as the compressed air was allowed to escape, the caisson would lose a considerable, perhaps vital, part of its support. During one of the earlier fires the river had been allowed to rush under the shoe as air was released and a uniform pressure had been maintained until the fire was out. Moreover, the load being borne then was quite light, comparatively speaking. But now the water would have to be poured down the water shafts from above. The supply might be limited, more than likely it would be variable, and so there was a chance the air might get out before the water reached the roof. In that event, of course, the caisson and all it carried would drop suddenly and the blow would probably be enough to destroy all supports.

  To compound the problem, one water shaft was resting on several boulders at that particular moment. It had been capped above earlier, drained, and a gang of men were busy that same night digging the boulders out. But if the caisson were to be flooded immediately and settled abruptly as a result, even if only a foot or so, the water shaft would smash down on the boulders with such force as to wrench it permanently out of kilter. And this, quite likely, would leave the caisson leaking so badly that it could never be inflated again.

  About three in the morning, water began to drip from the charred seam for the first time, suggesting that the compressed air had driven water into every possible crevice above, that the timber was now totally saturated for fifteen feet up, and that the fire was at last out.

  Roebling was so exhausted he could barely stand. He had been in the caisson much of the previous day and had gone home that evening completely played out. The air was also bothering him a good deal. The men now urged him to leave. Then, about five o’clock in the morning, having decided that the fire was out, he had what appears to have been an almost total physical collapse. The accounts there are do not say exactly what his condition was, only that he had to be helped up through the air lock.

  Apparently the sharp night air revived him some at first, but then suddenly he felt the beginnings of paralysis. In a matter of minutes he was unable to stand or walk. Nearby, Charles Young, the foreman, who had also been carried up through the lock about the same time, was in an equally bad state.

  Roebling was driven directly home in a carriage just as it was turning light. For the next three hours he was rubbed vigorously all over with a solution of salt and whiskey. It was the best way to restore circulation they believed. He was conscious the whole time and he was in no pain apparently. After a bit, with a little help, he was able to get up and walk about, but he was very weak.

  At eight, or thereabouts, a man was at the front door with a message. Fire had been discovered again deep in the caisson roof. Roebling dressed and returned immediately to the caisson.

  He was down only a few minutes this time. The carpenters had drilled four feet into the overhead timbers and discovered that the whole fourth course of pine was a mass of living coals. The caisson would have to be flooded, Roebling said. It was a last-ditch decision and he made it on the spot, without any hesitation.

  In his absence the men working on the boulders beneath the water shaft had succeeded in removing them, so that at least was one worry he could forget about. He ordered the men all up to the surface. An alarm was sounded in the yard and it was only a matter of minutes after he himself had come up out of the air lock that fire engines were clanging through Brooklyn toward the river with hundreds of people chasing after them.

  The time was just about nine. Rumors were everywhere. People were saying there had been a terrible explosion beneath the river, that the caisson had been ripped apart, that half the men had been killed and the rest were still trapped below. At the ferry slip, along Fulton Street, Water and Dock, noisy crowds gathered, everybody trying to find out what was happening and nobody able to see very much. The best view, as usual, was from one of the ferries. But hundreds of people worked their way right into the bridge yards, mingling among swarms of firemen who were rolling out hoses from what appeared to be every last fire engine in Brooklyn. On the river, a New York fireboat and two tugs were being brought up alongside the caisson.

  “The crowd dispersed, re-gathered, looked here and peered down there to discover the dread destroyer,” the Eagle reported later in the day, “but to the general eye no fire was seen.”

  Men, muddied by splashing liquid clay, dampened by the streams of bursting hose, made their difficult way over all obstacles, climbed upon the elevation whence the water shaft is accessible, and looked down, only to see the unrevealing surface of the column of muddy water, with which the shaft is filled. Others again, climbed upon the platform about the air lock, up and down in which the huge rubber pipes go, and in pursuit of knowledge under difficulties, climbed down as far as they might.

  Before the morning was out it seemed the whole of Brooklyn had been down to the river’s edge. A double line of police was needed to keep back the crowd. “Everybody was there,” the Eagle said, “and there was considerable lively calculations going on. Persons in every walk of life wandered about the spot, Senators, merchants, laborers. To most of them the whole thing was a mystery.”

  It was in tr
uth the damnedest fire anyone could remember seeing. There was no flame, nothing to be seen burning, not even much smoke. In some respects the scene was more like that following a mine disaster, the trouble all concealed below, unexplained and out of reach, except here there was no anguish over human suffering, not even much indication that things were serious. Were it not for rumors and the anxious looks of a few officials, no one would know there was any particular trouble below. The idea that there was even a fire had to be taken pretty much on faith.

  About the closest thing to real excitement the whole morning was the bursting of a hose that sent up a spectacular plume of spray “upon which the sunlight played,” said the Eagle, “forming a beautiful, clearly marked rainbow, with a fainter one reflected on the mist and spray from the streams.”

  A grand total of thirty-eight streams were pouring into the water shafts by ten o’clock, eight from the fireboat, five from the tugs, the rest from fire engines, including two or three brought over on the ferry from New York. One tug alone was pumping eight thousand gallons a minute and estimates were that inside the caisson the water was rising across the entire interior about eighteen inches an hour. But even at this rate it would be another five hours anyway before the chambers were flooded to the top, and therefore it would be that long or longer until the water did any good, since the fire was all in the roof. So fire, fed by compressed air, would be eating through the timberwork with nothing to restrain it until at least three in the afternoon, which accounted for the “degree of anxiety” noted “on the faces of those familiar with the character of the works.”