. Annual report. 1st-12th, 1867-1878. theGrand. Where the tributaries of that stream leave their caiions, thelatter have walls 3,000 feet in height, while the plateau edge is but 400feet lower than the divide between the two rivers. We have, therefore,in this instance, one of those peculiar cases which could be explainedby the same assumption that Professor Powell claims for so many ofhis observations in the region of the Colorado River. This explana-tion asserts that during the period in which flowing water followed ap-proximately the same courses as to-day, the southern edge of this pla-teau
. Annual report. 1st-12th, 1867-1878. theGrand. Where the tributaries of that stream leave their caiions, thelatter have walls 3,000 feet in height, while the plateau edge is but 400feet lower than the divide between the two rivers. We have, therefore,in this instance, one of those peculiar cases which could be explainedby the same assumption that Professor Powell claims for so many ofhis observations in the region of the Colorado River. This explana-tion asserts that during the period in which flowing water followed ap-proximately the same courses as to-day, the southern edge of this pla-teau would have been elevated; that the erosive power of the waterwas more than adequate to the rapidity of the elevation, and that, inconsequence, the water maintained its own former level, while the caiionwalls grew higher and higher. No doubt this view is a very ingenu-ous one, and, if applicable anywhere, it would seem that here in thesesoft shales there was an excellent opportunit3r for its consummation. 7ZS. Geol, Survey. Plate VT. •MoTvaments irv Wahsatbh Group. AM. PHOTO-LITHO. CO. (OSBORNES PROCESS.) GREEN RIVER GROUP. 83 I am opposed, however, for many reasons, to an explanation that would,if correct, necessarily bo corroborated by other facts, the existence ofwhich we nowhere observe. I have not had an opportunity to studythe localities which Professor Powell has examined. It is therefore notmy place to enter into any discussion upon a question of which I auipersonally acquainted with but one side. Proceeding westward from this area we reach the divide between Pte-ce-ance and Douglas Creeks. Upon this a number of stations are located,some of them being the most prominent within the district. On theeast side of tbis divide the narrow ridges, separated by steep canons,gently slope toward Pte-ce-ance. Within a horizontal distance of twentymiles these ridges fall approximately 1,800 feet, retaining a very evenangle of slope, however. West of the divide the sl
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