Early last fall I gave a talk at Merrimack College in North Andover, Massachusetts, about 25 miles north of Boston. After the question-and-answer period, an engineering professor introduced himself to me and asked if I had seen the historic bridge in front of the college's science and engineering building. I had known there was a reconstructed iron bridge on the campus, and I was grateful for the reminder. On our way off campus, my wife and I took a slight detour, and I am glad that we did. Seeing the 150-year-old bridge motivated me to seek out information about its design and its engineer, which in turn led me to a fascinating bit of technological history.
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