The naturalist & explorer Alexander von Humboldt (1769-1859) achieved unparalleled fame in his own time, particularly in the U.S. Here, Sachs traces Humboldt¿s influence on Amer. history, specifically looking at the lives & careers of several 19th-cent. explorers who used Humboldt¿s notion of ¿unity in diversity¿ & his spirit of exploration to develop a critique of their increasingly industrialized society. Includes: J. N. Reynolds, who explored the South Seas from 1829 to 1831; Clarence King, first dir. of the U.S. Geol. Survey; George Melville, Arctic explorer & chief engineer of the U.S. Navy; & John Muir, explorer of Alaska & Siberia. Discusses the Amer. writers & artists indebted to Humboldt, incl. Emerson, Whitman, Thoreau, Melville, Poe, & Frederic Church.