. Report of the geological exploration of the fortieth parallel . f the most interestinir and character-istic canons of the range. This stream takes its rise between Bald I\Iount-ain (11,977 feet) and ilount Agassiz (13,000 feet), in an almost circularamphitheatre from 4 to G miles in diameter, studded with shallow mountain-lakes, which occupy glacier-worn basins in the horizontal quartzites, withan average elevation of 10,000 feet above sea-level. It then flows for about10 miles nearly due south through a deep U-shaped canon, cut from 2,000to 3,000 feet into the hard quartzite strata, with al
. Report of the geological exploration of the fortieth parallel . f the most interestinir and character-istic canons of the range. This stream takes its rise between Bald I\Iount-ain (11,977 feet) and ilount Agassiz (13,000 feet), in an almost circularamphitheatre from 4 to G miles in diameter, studded with shallow mountain-lakes, which occupy glacier-worn basins in the horizontal quartzites, withan average elevation of 10,000 feet above sea-level. It then flows for about10 miles nearly due south through a deep U-shaped canon, cut from 2,000to 3,000 feet into the hard quartzite strata, with almost perpendicular walls,■which, when seen from Ixdow, with the bare summit of Bald ]\[ountain attlie head, gives an eftect somewhat like that of the Yosemite Valley, socompletely does it seem to be shut in. Reaching the steeper-dipping-beds,its course is somewhat deflected, and, in the softer IMesozoic rocks, it hascut a broader valley, flowing through a wide alhivial liottom out into theregion of Tertiary benches and plains. U^S 40Parallel PLATE X. < < < < & % ^fc.^fe^^^^ DUCHESNE FORK. 313 In this canon, a section is afiforcled almost at riglit angles to the strike,and all the beds from the Weher Quartzite to the Tertiaries of the UintaValley and the WAoming Conglomerate are shown with more or less dis-tinctness. The shallow dips of 5° and 10° continne from the head of thecanon down to within about 3 miles of Stanton Creek, the main westernbranch of the Duchesne. On the broad flat surface of Rhodes Spur, whichforms the western Ijoundary of the main canon, tlie drab limestones of theUpper Coal-Measures are left for a considerable distance in the shallowerdijDS. From them, the following Carboniferous species Avere obtained: Chonetes fZaphrentisfLifJwstrotion?Enomplialas? Of these fossils, the two latter would seem to indicate a lower horizonthan the Upper Coal-Measure series, having
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