| Timothy O'Sullivan (possibly) / William Bell (possibly) Rock carved by the Colorado 1871-1875 (ca) Collotype Rijksmuseum RP-F-2001-7-794-6 LL/79114 George M. Wheeler et al., 1875, Report upon Geographical and Geological explorations and surveys west of the One Hundreth Meridian, vol. III - Geology, (Washington [D.C.]: Government Printing Office)
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