Bridges change the world. Because of them, people and goods can travel from place to place, crossing wide, swift rivers easily and quickly. They play a vital role in our lives today—and we take them too much for granted.

But these complicated, delicate structures don't just happen. It takes years of careful planning and work to sink foundations, calculate stresses and loads, and build just the right span for each bridge. This book tells how cofferdams are sunk; the way caissons operate—and the thrilling story of the sandhogs who work in them at the river bottom; the basic principles behind fixes spans, movable and floating bridges, and how men risk their lives high above the water to build them.

This clear, simple explanation of the "hows" and "whys" of bridge construction from earliest times to the present is accompanied by many helpful pictures and diagrams. Handsome picture spreads of famous and unusual bridges, a glossary of special bridge terms, and tables of information on notable modern bridges combine to make this a welcome addition to the popular FIRST BOOKS.

Publisher recommendation: Grades 3-7

From the dust jacket