Smith was, in fact, a keen and intelligent observer and deserves great credit for his work. His thesis of slower decompression was the key to the puzzle. The only problem was he did not carry it anywhere near far enough.
A man’s health did depend mainly on how sudden and great a change he was subjected to on coming out of the caisson back to normal pressure. If there was to be damage done it happened then. Time in the caisson, the amount of pressure the men were working under, their individual physical make-up and condition, even the temperature both in and outside the caisson, were all important contributing factors. But it was the speed of the exit that really mattered. And by modern standards the men in the New York caisson were making their exits disastrously fast—even when doing as Smith wanted and taking a few extra minutes in the lock. Today the accepted safe rate of decompression is no less than twenty minutes for each atmosphere, or more than a minute for every pound of pressure. So by that standard, at a depth of sixty-five feet in April of 1872, every man coming up from the New York caisson should have spent at least twenty minutes in the lock, instead of two or three as was the average, or five or six as Smith urged.
That bubbles of nitrogen were the true cause of the dreaded disorder had already been discovered in France by a professor named Paul Bert, and at about the same time Smith was conducting his research. But the discovery would not be published until August of that year, and although Smith would read what Bert had concluded before formally presenting his own conclusions, he would decide that Bert was mistaken.
Smith was quite right about one other very crucial matter: how to relieve the agony of the disease. Just when the answer dawned on him is not clear, but it appears quite noticeably twice in his case notes.
The first time was in February, in the case of the foreman Joseph Brown, already quoted. “Pain continued until he went down again for the afternoon watch, when it ceased immediately.” Then in April, Smith described the case of another foreman named Card, who was hit by an attack of extreme trembling, followed by paralysis in the legs and bladder. Smith writes that the man remained in this state for two full days, but then adds, “After the paralysis had passed off in a measure, he went down again into the caisson and remained for a short time with decided benefit.”
The quickest, surest way to relieve the pain was to send the patient right back into compression and when it came time for Smith to present his final report the next year he would write this:
It frequently happened under my observation that pains not sufficiently severe to deter men from returning to work were promptly dissipated on entering the caisson, to return again on coming into the open air. Indeed, I do not remember a single exception to the rule, that any pain which may have been felt before, disappeared almost immediately on going down.
Smith was aware, too, that Pol had prescribed returning the patient at once to the compressed air and that Dr. Antoine Foley, also of France, had said the same thing in a paper published in 1863. Later that same spring of 1872, in his own annual report, Roebling would write that most men got over their troubles either by suffering for a time or “by applying the heroic mode of returning into the caisson at once as soon as pains manifested themselves.”
But the puzzling thing is that Smith never seems to have actually prescribed this “heroic mode.” Not once, according to the records, was a man suffering from a violent attack of the bends taken back down into the caisson. It was only the man who felt fit enough to go down on his own, to work, who ever benefited from this simplest and most effective of all remedies. Smith’s explanation was that the means of access to the caisson were such that to take any but a comparatively healthy patient down inside would have been too difficult—“even if he could be comfortably cared for while there, or if his presence would not interfere with the work.” The remedy was just too much bother, he seems to be saying. It would have deterred progress the same as would more time taken in locking out.
But equally important, it seems, was the fixed idea most of the men had that the pressure itself was the cause of the trouble. They could not get rid of that idea. The thought of going back for more pressure when they were in their agony—of getting back on the horse, so to speak—was more than any of them were up to and particularly if neither the doctor nor the engineers in charge ever insisted on it. The less risky course seemed simply to hold on and suffer it out.
At a depth of sixty-eight feet the caisson’s steady plunge into the earth slowed abruptly. The men were into quicksand now and the going became extremely tedious. The big clamshell dredge buckets dropping down the water shafts were almost useless against the fine sand that, in combination with small stones and boulders, had compacted into a substance about as hard as rock. The teeth of the buckets made hardly any headway at all. The point of a crowbar could be hammered into the material, but just barely. And though the sand pipes still “answered admirably,” as Roebling put it, even they were constantly clogging with coarse gravel and stones. The speed of descent was now perhaps a foot a week.
At a depth of seventy feet Roebling ordered that daily soundings be taken for bedrock. So a couple of men with sledge hammers and a ten-foot iron rod began probing the work surface and among the others there was talk of the caisson going twenty or thirty feet more before Roebling would call a halt. Then at a depth of seventy-one feet the first death occurred.
On the morning of April 22, a heavy-set German, a common laborer, went down through one of the air locks and into the caisson for the first time. Two days before, when he applied for work, the man had given the name of John Myers. Dr. Smith had judged him to be about forty and in good health. The pressure by this time was thirty-four pounds, and the workday, shortened once again, was five hours.
According to Smith’s subsequent account of the case, Myers worked the morning shift, just two and a half hours, without any discomfort, and hung about the yard for nearly an hour after coming up, apparently heeding the doctor’s rules about rest. But then he had complained of not feeling well and started for his boardinghouse, which was quite close by. “As he passed through the lower story of the house,” Smith wrote, “on his way to his room, which was on the second floor, he complained of pain in the abdomen. While ascending the stairs, and when nearly at the top, he sank down insensible, and was dead before he could be laid upon his bed.” An autopsy at the city morgue showed that brain, heart, and kidneys were perfectly normal. The lungs, however, as Smith reported, were “congested to a very remarkable degree.”
On April 30, just eight days later, with the pressure still at thirty-four pounds, Patrick McKay, of Ireland, age fifty, was listed as the second fatality attributable to the caisson disease. McKay had been working in the caisson for four months with no ill effect. On the afternoon of the 30th he had stayed down a half hour longer than usual, and on his way out through the lock, the others in the lock saw him suddenly slump to the floor, his back against the iron wall, quite insensible. He was at once carried into the open air and taken to Park Hospital, where Smith looked in on him some time later that evening. “He was there in an unconscious condition,” Smith wrote in his notebook; “face pale and dusky; lips blue; pulse irregular and feeble. Under the administration of stimulants, he recovered some degree of consciousness, and begged incessantly for water.” But only a little later the man went into convulsions and died. This time, however, the autopsy indicated Bright’s disease in the kidneys and Smith would conclude that “the effect of the compressed air was merely to hasten an event which, at best, could not have been very long delayed.”
Be that as it may, the word was out—not just among the work crew, but everywhere in the neighborhood of the bridge—that men were dropping dead of caisson sickness. A third man who had died some time earlier of spinal meningitis was also said to have been a victim, “if the truth were known.” The stories became greatly exaggerated and spread like wildfire through the crowded tenements near the site of the New York tower.
One of the children to gr
ow up on South Street in the 1870’s was Al Smith, who would one day be almost as much a symbol of New York as the bridge itself. In later years he would describe his mother talking in tones of awe about the many workers who had died while struggling to sink the great caissons. “Perhaps if they had known,” she had said, “they would never have built it.”
On May 2 a man named Heffner began vomiting and despite everything done for him he was still vomiting twenty-four hours later. On May 8 the entire force of caisson men went out on strike. They stood about in the street nearby, talking to newspaper reporters and anyone else who would listen. Conditions below had become so dangerous, so terrifying, they said, that they wanted three dollars for a four-hour day. By noon or thereabouts the Bridge Company had agreed to $2.75, but the men turned that down angrily and a man who tried to break through their lines was badly beaten. Negotiations dragged on for another three days. But then William Kingsley announced that if the men did not all go back to work immediately he would fire every last one of them and with that the strike ended.
There were more attacks of the bends during the next week and the caisson kept descending little by little. From the soundings Roebling had ordered, a picture of the underlying bedrock had begun to emerge.
“The surface was evidently very irregular,” he wrote, “composed of alternate projections and depressions, the extreme difference in elevations encountered being 16 feet, and occurring chiefly along the water edge.” Throughout the central section, however, and covering at least two-thirds of the entire area, the irregularities were much less, amounting to maybe no more than three or four feet. As near as he could tell, the caisson was about to settle on a broken ridge of rock running diagonally from one corner of the caisson to the other and having a dip of perhaps five feet in a hundred toward the land, but falling off rapidly toward the east.
Roebling now faced what would be the most difficult decision of his career. He himself was very near to a physical collapse. He had been spending as much time in the caisson as anyone, but going up and down through the locks, to check on this or that below, many times more often than the average laborer. He was on the job constantly, working twelve to fourteen hours a day, six days a week, frequently making three and four trips a day on the ferry, going back and forth from the Brooklyn offices. Most of his time was spent on the site itself. But it was the only way he could have worked. He was not an office engineer and had little regard for those who were.
At this point he could either keep the caisson descending until he had level rock on which to leave it or he could stop about where he was, before reaching rock. To continue deeper would mean enormous expense and time lost blasting the irregular rock ridge down to a comparatively even surface. It might also mean more lives lost. Already Smith had recorded more cases of the bends than Jaminet had in St. Louis. And whereas Eads had not suffered a single fatality until his first caisson was down ninety-four feet and the pressure was at forty-four pounds, Roebling, for some unknown reason, had already lost two men. So at this rate the New York caisson might take even more lives than the thirteen the St. Louis foundations had cost by the time they were in place.
Emily Roebling would remark later that her husband estimated it would take another year to go to bedrock and that it would cost another half a million dollars and possibly a hundred lives.
To leave the tower standing on anything other than bedrock, however, would seem to put the stability of the entire bridge in jeopardy. Yet Roebling, to the surprise of many, was now not so sure about that. The sand and gravel covering the rock was so compact, so very hard, he said, that it might provide as solid a footing as rock itself. Earlier, when they were down sixty feet or so, the men had uncovered the bones of a domestic sheep, and just below that fragments of brick and pottery, indicating that the strata at that level had changed within the time man had been around. But in the last ten feet and more, no such evidence had been unearthed; the strata showed no signs of having been disturbed since the time of deposit several millions of years in the geologic past and so in all likelihood it would remain perfectly stable. As Roebling noted, it was now nearly impossible to drive in an iron rod without battering it to pieces. The material, he would write in his forthcoming report, was “good enough to found upon, or at any rate nearly as good as any concrete that could be put in place of it.”
If he was right about this, then the enormous stone tower could rest there as well as anywhere and his problems would be solved. But if he was wrong, then there was the chance that the tower might begin to lean or slip and the bridge would be a disastrous failure. Possibly, others noted, the tower might even slide into the river.
“The period of time at the end of the sinking of the New York caisson was,” his wife would say, “one of intense anxiety for Colonel Roebling.”
But the decision could wait a little.
At a depth of seventy-five feet the first spur of bedrock, the ordinary gneiss of Manhattan Island, was encountered under the shoe on the river side. “No part of its surface shows the rounding action of water or ice,” Roebling reported. “On the contrary, the outcrop is in the form of sharp thin ridges, with steep vertical sides occurring in parallel ranges.”
On May 17 one man became paralyzed in the legs and arms; another complained of savage pains in his legs; a third, an Englishman named Reardon, began retching violently after coming up from the afternoon shift. In minutes he was seized by excruciating leg cramps and pitched forward, unable to walk or stand. The vomiting continued all night and Dr. Smith had him taken to the Center Street Hospital, where he grew steadily worse. The following morning he died. Smith wrote in his notebook that Reardon had been “corpulent” and that the autopsy showed his spinal cord to be “intensely congested.”
That same day, May 18, 1872, with the caisson at a depth of seventy-eight feet six inches, Roebling ordered that the digging stop. He had decided not to go to bedrock, staking his reputation and career on the decision. The New York tower would rest on sand.
The second and last great caisson was therefore in position, and as Collingwood noted, the differences of level at the extreme corners, as measured on the masonry above, was only three-fourths of an inch. It had been a spectacular feat of engineering.
The work of filling the air chamber began at once and Roebling finished his report to the directors. If anyone was upset about the incidence of caisson sickness, Roebling said only that the trouble had not been so serious as he had anticipated. He made no mention of the number of cases there had been and claimed that just two deaths could be charged directly to the effects of pressure. As for the unsung individual suffering there had been, he said only this: “The labor below is always attended with a certain amount of risk to life and health, and those who face it daily are therefore deserving of more than ordinary credit.”
At the end of May, Dr. Smith resigned his position and went back to the Eye and Ear Hospital, satisfied his work was complete, his services no longer needed now that the caisson was at rest. But work inside the caisson continued right along, the concrete for filling it in being mixed above, then let down through the supply shafts. No brick piers were built this time; the caisson was quite strong enough on its own. (With 53,000 tons on its back, it showed not the slightest sign of deflection in the roof.) But about a third of the space was filled with stones, earth, and sand left inside during the sinking. With the concrete going in at the rate of one hundred cubic yards a day, Roebling figured to have the entire job done by early July. The saying was that the concrete would keep pouring into the caisson until there was room enough left for one last Irishman, who would make his final exit by one of the water shafts.
But some time before that happened, Roebling suffered another attack of the bends. There is nothing in the official record to indicate just when it happened, only that it was late spring, while the concrete work was going on. Apparently he collapsed again, as he had the night of the Brooklyn caisson fire, and he was immediately taken back to Brooklyn
on the ferry.
Who was on hand to help him is not known. There would be nothing said of the incident in the papers, suggesting that perhaps he and the others wanted no more adverse publicity than they already had or that they thought the seizure would soon pass. He himself made only the briefest mention of what happened in a report published later that fall. The attack, he said, resulted from a stay of several hours in the caisson, suggesting that he still believed the time spent below was the determining factor and had never accepted Smith’s theory on speed of decompression. “Relief from the excruciating pain,” Roebling wrote, “was afforded in his [the writer’s] case by a hypodermic injection of morphine in the arm, where the pain was most intense, and a further stupefaction by morphine, taken for twenty-four hours internally until the pains abated.” According to Emily Roebling, however, in an account written a few years later, his condition was so serious the night of the attack that he was expected to die before morning.
There is no telling whether Smith was called back, whether the idea of returning to pressure (“the heroic mode”) was even considered, or if so, why it was rejected in favor of drugging the patient into a stupor.
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