Through the story of the 1907 Quebec Bridge disaster, in which seventy-six men died, author Dan Levert teaches a powerful object lesson in what can happen when that Obligation is forgotten. Woven from transcripts of the inquiry into the collapse, the report of the commissioners, and other sources including the coroner's inquest, On Cold Iron plays out like a fast-paced thriller. Levert recounts the original 1850s proposals to bridge the St. Lawrence near Quebec City, through the design and construction of what was to be the longest clear span bridge of any kind in the world, to its shocking collapse during construction in August 1907. The missteps, poor policies, hubris, and wrong-headed actions begin to build like a death by a thousand cuts, until its inevitable and horrifying culmination. The meticulously researched and deftly delivered story of this terrible historical event makes fascinating reading for anyone, but even more, it is a powerful cautionary tale and a clarion call for the obligation and responsibility of an engineer.