John K. Hillers 1873 Trachytic rocks [Sevier Series.] [U.S. topographical and geological survey of the valley of the Colorado River of the west, by J.W. Powell and A.H. Thompson. No. 040]
Stereoview Library of Congress, Prints and Photographs Division Reproduction Number: LC-DIG-stereo-1s00796 (digital file from original photo, front) LC-DIG-stereo-2s00796 (digital file from original photo, back) LC-USZ62-92670 (b&w film copy neg.)
