"We have needed ways to cross valleys, rivers, and mountains for as long as there have been people on Earth. Over time, scientists and engineers began to understand the laws of nature that apply to bridges and tunnels. They understood the strengths and weaknesses of materials better, too--and began to create new ones, like concrete and steel. This . . . guide to bridges and tunnels explores unique examples of each, what they're made of, and all of the unexpected twists and turns taken in their development"--Provided by publisher.
