<DIV><p>In 2009 the University of Utah Press and the Utah State Historical Society co-published three volumes of long out-of-print journals, letters, and other documents from John Wesley Powell's expeditions down the Colorado River. We are proud to announce the fourth and final volume. <I>Cleaving an Unknown World </I>collects Powell's journal (<I>Smithsonian Journal of History</I>, 1968); Jack Hillers's diary and photographs, previously published as <I>Photographed All the Best Scenery</I>, edited by Don D. Fowler (University of Utah Press, 1972); original maps from Francis Marion Bishop (<I>Utah Historical Quarterly</I>, 1969); Frederick S. Dellenbaugh's letters (<I>Utah Historical Quarterly</I>, 1969); and John C. Sumner's journal from the first Powell expedition (<I>Utah Historical Quarterly</I>, 1969). Roy Webb's foreword provides the context for these disparate pieces.</p><p>This beautifully illustrated book features Hillers's photographs—long regarded as a remarkable and unique record of the Colorado River and the Grand Canyon. <I>Cleaving an Unknown World </I>belongs in the library of any reader interested in the exploration of the American West.<BR>  </p></DIV>