380 DESCRIPTIVE GEOLOGY. 



lateral pressure, and that a distinctly-bedded rock may be easily compressed 

 into one which possesses no evidence of bedding except its being bounded 

 above and below by distinctly-stratified rocks, and that the result of this 

 compression may act very unequally on different zones of the same series, 

 giving rise to the appearance of an eruptive rock lying between two mem- 

 bers of a stratified series. That they are not eruptive rocks is clearly to be 

 found by following them out on the strike, where they may almost always 

 be traced into distinct stratification. • 



On the east slope of the range, directly east of Farmington, at the edges 

 of the Tertiary strata, but separated from the Farmington Archsean by great 

 masses of earth and Tertiary debris, is a body of peculiar dark purple quartz- 

 ite, containing large pellucid grains of quartz, and rounded pebbles up to 

 half an inch in diameter. In its dip and strike, it is apparently conformable 

 with the Archsean schists, but, owing to the broken character of its beds, no 

 great weight can be given to this appearance, and, from its close resemblance 

 to almost identical bodies of quartzite found among the Cambrian rocks in 

 other parts of the range, it is probable that it belongs to this series; it has 

 not, however, been indicated on the map. An analysis of this rock gave : 



SiHca 94.04 ' 94.06 



Alumina : ' 3.55 3.60 



Ferric oxide - 0.59 0.60 



Lime .-- -- 0.12 0.14 



Magnesia 0.06 0.05 



Soda--.. - - 0.30 0.24 



Potassa 0.76 0.79 



Ignition 0.44 0.46 



99.86 99.94 



East Canon Creek. — The area between the east slope of the Wah- 

 satch and the valley-bottom of the Weber is occupied by a broad plateau 

 of Tertiary sandstones and conglomerates, belonging to the Vermillion 

 Creek series. Through this plateau is cut East Cation, a narrow valley 

 about 4,500 feet deep, whose flanks slope back with considerable regularity 

 to the high hill-tops on either side; it is only in its lower portion, about 6 



