BOX ELDER REGION. 403 



which leave a very considerable deposit of ferruginous salts. To the north 

 of Willard Peak, the Archaean rocks gradually sink, and are lost beneath the 

 plain and the ddbris which cover the slopes of the ridge toward Brigham City. 

 In a narrow gorge north of this peak is a pretty cascade falling over a straight 

 wall of Cambrian quartzite, which is here apparently deposited in a depres- 

 sion of the Archsean body. North of this point, and on the eastern slopes of 

 the ridge, the hills are so thickly covered by ddbris and soil accumulation 

 that no good outcrops were observed ; but, from the prevalence of quartzite in 

 the debris, it is evident that the upper limestones have been eroded away, and 

 the quartzites themselves probably sink beneath the plain. As these same 

 beds are, however, found in the range farther north, with the same easterly 

 dip, but set back on a line to the east of the axis of the Willard Peak fold, 

 and as no evidence was found of a synclinal fold to connect these two mon- 

 oclinal ridges, we must suppose the whole northern ridge to have been 

 faulted up in this region on a line corresponding with the valley of the 

 north fork of Ogden River. 



Box Elder Region. — In Box Elder Canon, which connects Brigham 

 City with a little mountain-valley, in which is the village of Copenhagen, 

 the beds of the Cambrian are again exposed in section. They consist of 

 quartzites and siliceous slates, with some micaceous schist, having a dip 

 varying from 30° to 70° to the eastward, with a strike of about north 15° 

 west. The quartzite is very similar to that found in Ogden Canon, a com- 

 pact, fine-grained rock, with a somewhat granular texture and slightly 

 reddish-yellow tinge. A specimen collected on the first high point north of 

 the canon possesses a vitreous lustre and conchoidal fracture, but it is so 

 fine as to show but little tendency toward the granular texture. Under 

 the microscope, its quartz grains reveal the presence of liquid-inclusions. 

 To the north of Box Elder Canon, the western foot-hills and the crest of 

 the range for two miles are formed of these Cambrian quartzites, which then 

 gradually sink toward the north, until, at Call's Fort, they disappear beneath 

 the plains. 



Directly east of the summit, in the low valley to the north of 

 Copenhagen Valley, there occurs a heavy bed of dark limestone resting 

 conformably upon the quartzite, which also forms a portion of the ridge to 



