Whether wading through the waters of the Columbia River or walking through the woods, biologist and history teacher Nisbet finds the remains of the Pacific Northwest's past and goes to great lengths to explain how these remnants got there. Nisbet (Sources of the River; Purple Flat Top; etc.), whose blood races when he touches ancient things, finds a trilobite fossil and is flushed with warmth, despite being knee-deep in icy water. He begins with historical accounts of trilobites and salamanders, and quickly moves up the evolutionary ladder to mammoths and even humans. He catalogues numerous historical encounters with California condors, including an amusing one in which naturalist John Kirk Townsend winged a condor along the Willamette River in 1835. Shedding his clothes and gun, Townsend crossed the river and, completely naked. battled the condor, which had a 10-foot wingspan, until he managed to knock the bird unconscious by hitting it with a well-thrown stone. The author also reports humankind's less victorious encounters with nature, including the terrible toll that smallpox and other diseases took on the Native American tribes of the Northwest. Although Nisbet's histories can veer into litanies (he cites more than 20 condor encounters), his passion and attention to detail will make this an informative read for nature lovers and historians of the Pacific Northwest. B&w drawings, map not seen by PW. (Oct.)