Eleventh annual report of the United States Geological and Geographical Survey of the Territories : embracing Idaho and Wyoming : being a report of progress of the exploration for the year 1877 . he usual dark gray or brown vesic-ular variety, holding small globules of white quartz which have a fusedappearance. It occurs in heavy layers, broken into irregular cross-frac-tured columnar fragments, and undulating as though the material flowedover an uneven surface. The same ledges appear in the bluff-face of thelower plateau bench that fills the opposite side of the valley, where, how-ever, they
Eleventh annual report of the United States Geological and Geographical Survey of the Territories : embracing Idaho and Wyoming : being a report of progress of the exploration for the year 1877 . he usual dark gray or brown vesic-ular variety, holding small globules of white quartz which have a fusedappearance. It occurs in heavy layers, broken into irregular cross-frac-tured columnar fragments, and undulating as though the material flowedover an uneven surface. The same ledges appear in the bluff-face of thelower plateau bench that fills the opposite side of the valley, where, how-ever, they appear to incline gently in the direction of the opposed mount-ain border. This appearance is not readiiy accounted for, unless theflows have been slightly tilted by forces acting in the mountain beltalong the southwest border of the valley. This high volcanic bench continues tbence to Pyramid Creek, every-where showing the same sloping surface outlying the sedimentarymountain border, across which numerous little streams have eroded deep,narrow channels, on their way to the river. On the opposite side of thevalley, corresponding benches are seen along the farther border of the PLATE Lower Valley of the SnctJce above Fall Cr*
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