In the chart of the Ellen cluster, Figure 38, an attempt is made to show the horizontal grouping of the laccolites and the order of their superposition wherever they overlap. It will be observed that where the limits are imperfectly known the outlines are left incomplete, and that the central area remains blank, not because it contains no trachyte masses, but because its alpine sculpture has prevented their study. Where it is not evident which of two encroaching laccolites is the superior, they are separated by a straight line. [Illustration: FIG. 40.—Section of the Lewis Creek Cañon through the Newberry Arch. 1, Henry’s Fork Conglomerate. 2, Upper portion of Flaming Gorge Shale. 3, Newberry Laccolite. ] The line _a a_ in the chart is the springing line of a broad, flat arch which underlies all the other arches of the western flank. If it covers but one laccolite, that one is the rival in magnitude of the Hillers nucleus, although widely different in proportions; but it is more probable that it contains a greater number. The upper surface is rolling and uneven, and has not the degree of symmetry which laccolites usually display. At the points _b_, _c_, _d_, and _e_ the altitude of the arch is 3,800, 3,500, 2,000 (estimated) and 2,500 feet. Nevertheless there is nothing in its simple outline to indicate a compound structure; the monoclinal ridges by which it is margined do not exhibit the flexuous curves which are commonly seen about the bases of confluent arches. Whether the nucleus is simple or compound it sends no branches to the surface; the only outcrops of trachyte belong to the overlying arches. The upper parts of the arch have been so carried away that the steepness of the mountain flank is not increased by it, and inferior strata are brought to the surface. At the north the crown of the arch bears the Henry’s Fork conglomerate, while beyond its base the plateau is built of Blue Gate sandstone. At the south the arch bears the Tununk sandstone, and the Masuk lies outside. [Illustration: FIG. 39.—The Newberry Arch and Laccolite. ] _The laccolite marked “E”_ on the chart rests upon the Tununk sandstone. The Blue Gate shale which once buried it has been all washed away except some metamorphosed remnants upon the top, and the trachyte itself has wasted to such an extent that its original form cannot be traced. The laccolite has no near neighbor, and the erosion has left it prominent upon the mountain flank. A continuous and solitary spur joins it to the central ridge.