580 DESOEIPTIVE GEOLOGY. 



ments ; and this is another instance in which marked peculiarities are pos- 

 sessed in common by the breccia fragments and the including paste. ■ It 

 seems to be a general rule in all the breccias that the paste and fragments 

 are precisely of the same material. To the east, the rhyolites fall off in long 

 spurs, and are overflowed by sheets of fine-grained basalt. 



In Wagon Canon is a limited outcrop of reddish quartzitic sandstone, 

 which is so similar to much of the rock in Agate Canon, while resembling 

 that of the River Eange, that it has been referred to the Weber Quartzite. 

 It is overflowed by a rough, gray sanidin-trachyte consisting of small sani- 

 dins, and laminae of more or less decomposed biotite. The microscope 

 reveals a large proportion of small particles of hornblende, entering promi- 

 nently into the constitution of the groundmass, which consists as well of 

 dull feldspars, and tolerably well-preserved hornblende crystals whose color 

 was originally green. Both in habit and mineralogical constitution, this 

 rock shows close affinity to propylite, and would be so classed, but that 

 the orthoclase predominates over the triclinic feldspar. The peculiar look 

 of the biotite which is noticeable in hand-specimens appears, under the 

 microscope, to be due to the interposition, between the brown laminae of its 

 transverse sections, of colorless muscovite. A little apatite also occurs. A 

 somewhat fissile structure is given to the rock by the prominent parallelism 

 of the biotite. This body of trachyte forms a narrow zone about half a 

 mile wide and four miles long, lying between the foot-hill rhyolites and the 

 body of quartz-propylite which forms Pappoose Peak, The question of 

 age between the trachyte and the rhyolite, in the hills lying to the west of 

 it, is obscure, but it seems probable that the rhyolite is the younger. The 

 rhyolites of the foot-hills overlap the trachytes to the west and also the 

 small body of quartzite which lies along the western edge of the quartz- 

 propylite body, and connect with the rhyolites which surround the head of 

 the valley, lying between Wagon Canon and the Cluro Hills. 



Beginning at Pappoose Peak, and extending along the middle of the 

 range, across Wagon Canon, and up nearly to the Humboldt River, is an 

 irregular zone of quartz-propylite, probably part of the same eruption which 

 occupies the crest of Cortez Peak, and which has been overflowed, to the 

 south of Pappoose Peak, by the rhyolite body. It consists of a fine micro- 



