258 DESCRIPTIVE GEOLOGY. 



valley, surrounded by castellated peaks and ridges, formed of nearly hori- 

 zontal beds of the Weber Quartzite, but having already a slight inclination 

 of 3° to 5° to the southward. Jones's Pass, at the head of this valley, the 

 lowest point in the divide from the western limit of the map nearly to 

 Leidy's Peak, has an altitude of over 11,000 feet. From this saddle, the 

 trail descends the canon of the Ute Fork, in which the southerly dip 

 increases very gradually, being less than 10° at Emmons' Peak, while it 

 is only near the southern flanks of the range that the steep angles of 40° 

 to 45° are reached, and the overlying limestones of the Upper Coal- 

 Measures found. 



The form of the Tertiary ridge to the east of Smith's Fork, which is 

 covered by the Wyoming Conglomerate, would suggest that this formation 

 might resemble that of the Pliocene Conglomerate of California, in that it 

 had filled an ancient stream-bed in the Eocene Tertiaries, which, owing to 

 its being more resisting than the strata out of which it was cut, is left in 

 the present topography as a ridge. 



In the basin-like heads of Henry's Fork, next east from Smith's Fork, 

 which are thickly timbered, only quartzite formations are found; but the 

 low, sharp ridges which enclose them on the north, are evidently, as farther 

 west, outcrops of the harder limestones of the Upper Coal-Measure group. 

 On the northern spurs of Gilbert's Peak, the quartzite beds are found 

 dipping 42° north, up to within a few miles of its base. The beds which 

 form the peak itself have a slight southern dip, and are formed of purple 

 quartzite, with several strata of greenish clayey beds, about 100 feet in 

 thickness. These are entirely wanting in the upper 1,000 feet of the peak. 

 From the summit of this peak, an excellent view is had of the interior of 

 the range over the broad, shallow, glacier-formed basins at the head of the 

 various creeks which flow to the north and south, and the steep, narrow 

 ridges, formed of nearly horizontally-stratified beds of quartzite, whose 

 slope, when appreciable, is always to the south. From here, the axis of 

 the range is seen to have a northeasterly direction from the Tokewanna 

 Ridge to this point, probably bending outward still more to the north at 

 Smith's Fork, while to the eastward it assumes a general east and west 

 trend. The northern shoulders of the main ridge, to the eastward of Gil- 



