TOOELLE AND RUSH VALLEYS. 455 



terraces is called, is in g-eneral a dry plain of Quaternary gravel and soil, 

 supporting only a growth of sage-brush {Artemisia tridentata), but having 

 along the bottoms of a few streams, especially that of Clover Creek, some 

 alluvial soil. Eush Lake, a little sheet of Water hear the Stockton Hills, 

 receives the surplus Waters of the valley, and, though only existing as a lake 

 since the time of the settlement of this region, its waters have alread}?- a 

 slightly brackish taste. In the middle of the valley, near the southern limit 

 of the map, is a loW ridge, in which were found horizontal beds of a white 

 limestone, With a silky texture. When treated by acid, this limestone leaves 

 a pumiceous mass of glassy needles, which would indicate that it is a vol- 

 canic tufa which has been dejiOsited under water and become impregnated 

 with carbonate of lime. 



Since the completion of the field-work of the Survey, it is reported that 

 beds carrying coal have been discovered in the Valley-slopes on the east side 

 south of Rush Lake, where the Quaternary covering has been cut through 

 by a stream-bed. From the description given of the beds, it is evident 

 that they represent a sduthern extension of the beds of the Green Eiver 

 Eocene, which Were discovered, also carrying coal, on the edge of the Great 

 Desert, at the eastern foot of the Ombe Mountains* 



The low ridge of the Stockton Hills, between these two valleys, is made 

 up principally of quartzites of the Weber groupj but shows at the south- 

 eastern extremity a small development of limestone beds, which apparently 

 form the northern point of the Ophir City anticlinal. Opposite the north- 

 ern corner of RUsh Lake these limestones strike northwest, dipping steeply 

 to the southwest, and are overlaid in the hills farther west by quartzite 

 beds, whose strike gradually changes to north and south, preserving a gen- 

 eral westerly dip, as far as can be detected under the accumulations of 

 gravel and detrital material. 



Li the terrace-bench of the extreme eastern foot-hills of the AquI Mount- 

 ains, opposite the western end of the Stockton Hills, ridges of cherty white 

 quartzite are seen striking a little west of north and dipping 75° to the west- 

 ward. These are supposed to be a continuation of the beds of the Weber 

 Quartzite, with slightly inverted dip^ inasmuch as the adjoining beds in the 

 foot-hills of the Aqui Mountains^ which have about the same strike and 



