_The Dana arch_ bears the same relation to Mount Ellen and Jukes Butte that the Pulpit arch bears to Mount Hillers. The streams which flow down have truncated it, and afterward carved a system of cañons below the plane of truncation. The Henry’s Fork conglomerate overlooks it from the base of the Jukes laccolite on one side, and on the other margins it with a monoclinal ridge; and in the interval the Flaming Gorge and Gray Cliff rocks come to the surface. [Illustration: FIG. 45.—The Jukes Butte, as seen from the southeast, showing the Jukes Laccolite, resting upon the Dana Arch. ] _The Crescent arch_ is so perfectly truncated by the existing mountain streams that their flood-plains unite above it in a single broad slope. On the side toward the mountain there are a few insular hills of the conglomerate, and on the side toward the plateau the same rock lifts a low monoclinal ridge which circles about the base of the arch in a crescent. Within the crescent there are few outcrops, but it is probable that the Gray Cliff Sandstone is brought to the surface. Near the center a solitary thin dike juts forth, like a buoy set to mark the place where a laccolite is sunk. Judging the magnitude of the laccolite by the proportions of the uplift, it has a diameter of nearly four miles and a depth of 2,500 feet; and these dimensions indicate a volume of three and a half cubic miles. _The Maze arch_ covers a smaller area than the Crescent, but its height is greater. The drainage from the mountain crosses it on a number of lines, but there is no indication that at any recent stage of the degradation they have produced an even truncation. At present they divide the Gray and Vermilion Sandstones by so intricate a labyrinth of deep cañons that the whole area of the uplift is almost impassable. The monotony of red sandstone, for here all members of the Jura-Trias are brick-red, the variety of dip, complicated to the eye by oblique lamination, the multiplicity of cañons and ridges, conspire to give an impression of chaos from whatever point the tract is viewed; and even from the most commanding stations I was unable to make out completely the arrangement of the drainage lines. Still no faults were discerned, and it is probable that the Maze arch, intricate as it seems, is a simple circular dome. On the north it adjoins the Crescent arch, and the monoclinal ridges of conglomerate which margin the two at the east are confluent. On the south it adjoins rather more closely one of the low arches which have been referred to the Pennell cluster. On the west, or toward the mountain, it is probably met by other arches at its own level; but these if they exist cannot be fully known until the progressing degradation of the country shall have removed certain laccolites which lie above them and slightly overlap the Maze arch.