John Wesley Powell 
Exploring the Colorado River [EPUB ebook] 

When geologist Powell and his party of explorers first assayed the Colorado in 1869, it was North America’s longest stretch of uncharted river. This is the story of that three-month, thousand-mile excursion, told in the words of the men who negotiated and mapped the river, through their journals, accounts, and letters. Black-and-white illustrations.