At Home - Bill Bryson [113]
To ameliorate the sinking problem, nineteenth-century architects developed a technique of constructing a “raft” on which the building could stand, rather as a surfer stands on a surfboard. The raft under the Monadnock Building extends eleven feet beyond the building in every direction, but even with the raft, the building sank almost two feet after construction—something you really don’t want a sixteen-story building to do. It is a testimony to the skills of John Root that the building still stands. Many others weren’t so fortunate. A government office block called the Federal Building, constructed at a staggering cost of $5 million in 1880, took on such a swift and dangerous pitch that it didn’t last two decades. Many other smaller buildings had similarly abbreviated lives.
What architects needed was some kind of lighter and more flexible building material, and for a long time it seemed that that would be the one Joseph Paxton first brought to large-scale fame with the Crystal Palace: iron.
As a building material, iron was of two types: cast iron and wrought iron. Cast iron (so called because it is cast in molds) was great at compression—supporting its own weight—but not so good under tension and tended to snap like a pencil when stressed horizontally. So it made excellent pillars, but not beams. Wrought iron, in contrast, was strong enough for horizontal duty but was more complicated, time-consuming, and expensive to manufacture since it had to be repeatedly folded and stirred while it was still molten. As well as making it comparatively strong, the folding and stirring made it ductile—that is, capable of being pulled, rather like taffy, and bent into shapes, which is why decorative objects like gates are made of wrought iron. Together they were used in large-scale construction and engineering projects all over the world.
Curiously, the one place iron never caught on except incidentally was in housing. (Just once, as far as is known, did anyone of note try to use it extensively in the construction of a house—recall from Chapter VII that the bibulous, erratic architectural adventurer James Wyatt built a cast-iron “Bastille” for George III.) Elsewhere, however, iron went from strength to strength—until, that is, it was realized that strength was not actually its most dependable quality. The disturbing fact was that iron sometimes failed spectacularly. Cast iron in particular tended to splinter or fracture if it wasn’t cast perfectly, and imperfections could be impossible to detect. That became tragically manifest in the winter of 1860 at a textile mill in Lawrence, Massachusetts. There, one cold morning, nine hundred women, mostly Irish immigrants, were at work at their clattering machines when one of the cast-iron columns supporting the roof gave way. After a moment’s hesitation, the other columns in the row failed one by one, like buttons popping on a shirt. The terrified workers rushed for the exits, but before many could get out, the building collapsed with a roar that none who heard it would ever forget. As many as two hundred workers died, though remarkably no one bothered, then or afterward, to make a formal count. Hundreds more were injured. Many of those trapped inside were hideously incinerated as fires spread from broken lamps.
In the following decade iron’s standing suffered a further blow when a bridge over the Ashtabula River in Ohio collapsed as a passenger train crossed over it. Seventy-six people were killed. That accident was recalled with uncanny precision three years later, almost to the day, on the Tay Bridge in Scotland. As a train crossed it in bad weather, a section of the bridge gave way, hurling the carriages into the waters far below and killing almost an identical number of people as had died at Ashtabula. Those were the most notorious of the tragedies, but iron mishaps on a smaller scale were almost routine. Railway