Children have a natural interest in windmills, waterwheels, steam engines, canals, covered bridges, and the other raw material of industrual archaeology--but Weitzman's labored efforts to drum up enthusiasm, along with his blathery presentation of the actual subject-matter, may well turn them off. In any case, they'd be better served by straightforward, fully illustrated, factual works like Edwin Tunis's. The one topic Weitzman develops in unusual (and disproportionate) detail is the truss: how trusses work; the various kinds of truss bridge, who developed each and what they're called. (Later, assorted roof trusses are also displayed.) But even this highly technical material comes with patronizing hype: ""Sit down there in the shade, rest a minute, and look at some real nineteenth-century bridge engineering. Now, aren't you glad you stopped?"" In sum: much sales talk, some imaginary dialogues (""Whew!"" says the old miller), and disconnected bits of information.