On June 15 McLure wrote to Cooper: "In riveting the bottom chord splices of [the] south anchor arm, we have had some trouble on account of the faced ends of the two middle ribs not matching...This has occurred in four instances so far, and by using two 75-ton jacks we have been partly able to straighten out these splices, but not altogether."
Cooper replied: "Make as good work of it as you can, it is not serious. It would be well...in future work to get the best results in matching all the members before the full strains [forces] are brought upon them."
When work on the central, suspended span began in July--as the span crept out over the river--the rapidly increasing stresses on the compression members farther back became intolerable. The instability of built-up, latticed compression members in a major work under construction was poorly understood then, so key portions at the ends of the Quebec Bridge's weight-bearing lower chords were still unriveted, even as the stresses upon them grew insupportable with the steady outward advance of the span.
By early August the end details of the compression chords began to show signs of buckling. On August 6 McLure reported to Cooper that lower chords 7-L and 8-L of the south cantilever arm were bent. Cooper was troubled. He wired back with instructions, and with the almost plaintive question: "How did bend occur in both chords?"
On August 12 McLure informed him that the splice between lower chords 8-L and 9-L was now bent as well. Cooper's concern grew, but it was not shared in Phoenixville. Chief Engineer Deans insisted that chords 7-L and 8-L had already been bent when they left the shop. McLure insisted that they only began to show deflection after being installed on the bridge. The debate over chords 7-L and 8-L occupied the greater part of August. Meanwhile work continued, and the stresses on the lower chords grew.
On August 27 the crisis should have been obvious to all. A week before, chord 9-L of the south anchor arm had been only three-quarters of an inch out of line. On the morning of August 27 McLure measured it again. The deflection was now two and one-quarter inches. McLure wrote to Cooper immediately. Had he been more experienced, he might have sent a telegram, the way a younger Theodore Cooper had once wired Captain Eads at midnight years before.
As word of what had happened to chord 9-L of the anchor arm swept the bridge, gusts of anxiety swept along with it. By the end of the day B.A., Yenser, the Phoenix Company's general foreman on the bridge, decided to suspend work, saying that he feared for his own life and the lives of the men under his charge. The next morning he changed his mind and ordered work to continue. Chief Engineer Hoare of the Quebec Company endorsed this decision--there is some evidence that he may have requested it. He saw no immediate danger, and he was afraid that stopping work then might mean that it would not resume until spring.
Officials of the Phoenix Bridge Company continued to insist that all the bends detected in the lower chord members had been present before installation. They made no effort at all to explain how the deflection of chord 9-L had grown by an inch and a half in the past week.
Fear was everywhere on the bridge on August 28, while the men in charge at the site were paralyzed by a vacuum of authority. Hoare, the Quebec Company's responsible engineer on the project, was technically unqualified--and thus unable--to take command. After much discussion, he dispatched McLure to New York to brief Cooper in person.
Shortly before 11:30 a.m. on August 29, Theodore Cooper arrived at his Manhattan office and found Norman McLure waiting for him. McLure's letter of August 27 had arrived as well. Cooper read it, spoke briefly with McLure, and at 12:16 p.m. he sent a terse telegram to Phoenixville that read: "Add no more load to bridge till after due consideration of facts. McLure will be over at five o'clock."
Cooper was unaware that work was still going on at Quebec. He was under the impression, based on McLure's letter, that construction had stopped two days before. In his haste to catch a train to Phoenixville, McLure neglected to wire Cooper's decision to Quebec as he had promised to do, and so work continued through the afternoon.
Cooper's telegram reached Phoenixville at about 3:00 p.m. John Deans read it--and disregarded it. The workers stayed on the bridge. When McLure arrived at five o'clock, Deans and Peter Szlapka met with him. They agreed to meet again in the morning, when a letter from Phoenix's field engineer at Quebec was due to arrive. The letter would support the Phoenix Company's position that the chords had left Phoenixville slightly bent but serviceable. Almost precisely as the meeting adjourned, chords 9-L and 9-R of the anchor arm buckled, and the Quebec Bridge collapsed. (See Exhibit A3)
