. Annual Reports of the Department of the Interior for the Fiscal Year Ended June 30, 1900--Twenty-First Annual Report of the United States Geological Society. Fromthis point the great talus of porphyry fragments that extends fromthe tower to the very border of the stream may be best observed, andon either side the sandstone is seen to dip inward gently, forming aV-sha])ed sag of wide angle in which the apex is immediately belowthe great columns. The Jurassic section is approximately as follows, from the towerdown: Quartzite. Tancredia limestone. Smoky, fine-grained limestone, Belemnite shales
. Annual Reports of the Department of the Interior for the Fiscal Year Ended June 30, 1900--Twenty-First Annual Report of the United States Geological Society. Fromthis point the great talus of porphyry fragments that extends fromthe tower to the very border of the stream may be best observed, andon either side the sandstone is seen to dip inward gently, forming aV-sha])ed sag of wide angle in which the apex is immediately belowthe great columns. The Jurassic section is approximately as follows, from the towerdown: Quartzite. Tancredia limestone. Smoky, fine-grained limestone, Belemnite shales. Oyster bed. Bluff of tender buff sandstone (sometimes pink). C4reen shales. Thick shell bed, forming a hard band. Buff marl. (iypsiferous red beds (marl). Structure of the toicer.—The tower is sharply divided at a pointmore than a third of the distance from base to summit l>y a line thatmarks the beginning of the columns and a bench formed by the upper VENTY-FIRST ANNUAL liEPORT. lATO TEEPEE, FROM THE SOUTH, SHOWING HORIZONTAL JURASSIC STRATA BELOV JAGGAK.] MATO TEEPEE. 261 limit of the massive uncolumnar base. This massive lower portion isjointed variously, showing sometimes a flat, vertical, rough lamellarparting and in other places irregular joints (PI. XL). It contains not atrace of the perfect colunmar habit of the upper portion, which is seen,however, to merge into the lower portion locally where the columnscurve out and are lost in the massive bench. On the SSW. corner thebasal mass rises to a height of from 40 to 50 feet above the talus,and a narrow columnar band resembling a dike extends downwardand outward into the base from the curved lower portion of the uppercolumns. This band is about 40 feet wide. Seen from this side theupper columns slope back about 4° or 5° from the vertical on thewestern side of the tower and 10^ to 12° on the eastern side. Onthe southwest face of the tower the columns make a curve outward, oflong radius in a western direc
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